Introduction

volcano, vents or fissures in the earth's crust through which gases, molten rock, or lava, and solid fragments are discharged. Their study is called volcanology. The term volcano is commonly applied both to the vent and to the conical mountain (cone) built up around the vent by the erupted rock materials. Volcanoes are described as active, dormant, or extinct. The soil resulting from decomposition of volcanic materials is extremely fertile, and the ash itself is a good polishing and cleansing agent.

Occurrence

Volcanoes are found in association with midocean ridge systems (see seafloor spreading) and along convergent plate boundaries, such as around the Pacific Ocean's "Ring of Fire" (see plate tectonics), the ring of plate boundaries associated with volcanic island arcs and ocean trenches surrounding the Pacific Ocean. Continental volcanoes are also associated with converging plate boundaries, such as the volcanoes of the Cascade Range along the W coast of the United States. Isolated volcanoes also form in the midocean area of the Pacific apparently unrelated to crustal plate boundaries. These sea mounts and volcanic island chains, such as the Hawaiian chain, may form from rising magma regions called hot spots; an example of a continental hot spot is found atYellowstone National Park.

Volcanic Cones and Craters

Shapes of volcanoes include composite cones, or stratovolcanoes, with steep concave sides such as Mt. St. Helens in the W United States; shield cones have gentle slopes and can be relatively large such as the Hawaiian Islands; and cinder cones as Parícutin in Mexico, with steep slopes made of cinderlike materials. Explosive eruptions build up steep-sided cones, while the nonexplosive ones usually form broad, low lava cones. Cones range in height from a few feet to nearly 30,000 ft (9 km) above their base. Usually the cone has as its apex a cavity, or crater, which contains the mouth of the vent. Such craters are typically less than 1 mi (1.6 km) across, but larger craters, called calderas, ranging in diameter from 3 mi to—in a few instances—50 mi (5–80 km), are formed by particularly large eruptions (see crater).

Volcanic Eruptions

More than 500 volcanoes are known to have erupted on the earth's surface since historic times, and many more have erupted on the ocean floor unobserved by humans. Fifty volcanoes have erupted in the United States, which ranks third, behind Indonesia and Japan, in the number of historically active volcanoes. Of the world's active volcanoes, more than half are found around the perimeter of the Pacific, about a third on midoceanic islands and in an arc along the south of the Indonesian islands, and about a tenth in the Mediterranean area, Africa, and Asia Minor.

Evidence of extraterrestrial volcanic activity also has been found. Space probes have detected the remnants of ancient eruptions on earth's moon, Mars (which has the largest volcano in the solar system, Olympus Mons, 340 mi/550 km across and 15 mi/24 km high), and Mercury; these probably originated billions of years ago, since these bodies are no longer capable of volcanic activity. Triton (a satellite of Neptune), Io (a satellite of Jupiter), and Venus are known to be volcanically active. The volcanic processes that occur in the outer portion of the solar system are very different from those in the inner part. Eruptions on earth, Venus, Mercury, and Mars are of rocky material and are driven by internal heat. Io's eruptions are probably sulfur or sulfur compounds driven by tidal interactions with Jupiter. Triton's eruptions are of very volatile compounds, such as methane or nitrogen, driven by seasonal heating from the sun.

Terrestrial volcanic eruptions may take one or more of five chief forms, or phases, known as Hawaiian, Strombolian, Vulcanian, Peleean, and Plinian. In the Hawaiian phase there is a relatively quiet effusion of basaltic lava unaccompanied by explosions or the ejection of fragments; the eruptions of Mauna Loa on the island of Hawaii are typical. The Strombolian phase derives its name from the volcano Stromboli in the Lipari, or Aeolian, Islands, N of Sicily. It applies to continuous but mild discharges in which viscous lava is emitted in recurring explosions; the ejection of incandescent material produces luminous clouds. A more explosive volcanic eruption is the Vulcanian, where the magma (lava before emission) accumulates in the upper level of the vent but is blocked by a hardened plug of lava that forms between consecutive explosions. When the explosive gases have reached a critical pressure within the volcano, masses of solid and liquid rock erupt into the air and clouds of vapor form over the crater. The Peleean, derived from Mt. Pelée, is more violent, emitting fine ash; hot, gas-charged fragments of lava; and a characteristic superheated pyroclastic flow that travels downhill at great speed. Plinian, or Vesuvian eruptions, derives its name from Pliny the Younger, who described the eruption of Vesuvius in A.D. 79. The Plinian eruption is similar to Strombolian and Vulcanian eruptions with significant ash and pumice and pyroclastic flows, but it also produces a characteristic massive, sustained eruptive column of hot ash that can reach 28 mi (45 km) in height.

Eruptions are often accompanied by torrential rains caused by the condensation of steam. The erupted fragments vary in size, including minute particles of volcanic dust and ash, lapilli (cinders or pellets), bombs (rounded or ellipsoidal masses of hardened magma), and huge masses called blocks. Minute dust and ash and aerosols carried high into the earth's atmosphere can have a cooling effect on the climate, and significant amounts of chlorine and bromine gases ejected in large eruptions can reach the stratosphere and deplete the ozone layer. The dust and ash can also be a hazard to air travel. The 1783 eruption of Laki, S Iceland, had devastating effects on local livestock and, as result, the populace; the resulting sulfur dioxide haze that spread over parts of Europe is believed to have negatively affected the health of the inhabitants

Historical Volcanoes

Notable eruptions within historic times have been those of Vesuvius, in Italy (A.D. 79, 1906, and other times); Tambora, in Indonesia, where between 30 and 50 cu mi (125–210 cu km) of molten and shattered rock were blown into the air (1815); Krakatoa, near Java, material from which was sent 17 mi (27 km) into the atmosphere (1883); Parícutin, in Mexico, the volcano that began in a cornfield (1943); Hibok Hibok, on Camiguin island in the Philippines, which killed 84 people

(1948); Besymianny, in Kamchatka, where 2 cu mi (8 cu km) of material were hurled into the air (1956); the peak of Tristan da Cunha, whose eruption caused the entire settlement to be evacuated (1961); Agung, in Bali, which killed 1,100 people (1963); Mt. St. Helens in Washington, which exploded with an energy equivalent to 10 million tons of TNT, killing 35, with 25 missing (1980); El Chichon in Mexico, which expelled about 500 million tons of ash and gas (1982); and Mt. Pinatubo in the Philippines, which killed over 500 people and ejected over 2 cu mi (8 cu km) of material (1991). Other notable volcanoes are Cotopaxi and Chimborazo (Ecuador), Iztaccíhuatl and Popocatépetl(Mexico), Lassen Peak and Katmai (United States), Etna (Sicily), and Hekla, Katla, and Laki (Iceland). Mauna Loa (Hawaii) is the world's largest active volcano, projecting 13,677 ft (4,170 m) above sea level and over 29,000 ft (8,850 m) above the ocean floor; from its base below sea level to its summit, Mauna Loa is taller than Mt. Everest. In 1963 the birth of the volcanic island Surtsey near Iceland was observed. In November of that year events began with a submarine eruption along the Mid-Atlantic Ridge. Eruption followed eruption until they ended in June, 1967, by which time the island stood 492 ft (150 m) above sea level and covered an area of almost 2 sq mi (3 sq km). The island has diminished in size since then due to erosion.

Bibliography

See S. Van Rose and I. Mercer, Volcanoes (2d ed. 1991); F. Martin, Volcano (1996); H. Sigurdsson, Melting the Earth: The History of Ideas on Volcanic Eruptions (1999); H. Sigurdsson et al., ed., Encyclopedia of Volcanoes (1999); C. Oppenheimer, Eruptions that Shook the World (2011).

Introduction to Volcanoes

You've probably heard in the news about volcanic eruptions, or you might remember when Mount St. Helens erupted. Perhaps you've even seen an active volcano. Although they are often a destructive force, volcanoes are an amazing facet of creation. They come in a variety of shapes, sizes, and eruption types.

Volcanoes erupt when magma, red-hot liquid rock, seeps up through a vent in the earth. More violent eruptions occur when pyroclastic material - a mixture of magma, rocks, ash, and hot gases - is exploded upward by pressure caused by underground gases and magma.

When magma flows above the surface of the earth, it is called lava. Usually lava changes from bright red to duller red, gray, or black as air causes it to cool and solidify.

Volcanic eruptions vary in size and display. There are six common types of eruptions, with differing features. Plinian eruptions usually have thick lava and high gas content. They can shoot pyroclastic material high into the air, moving at hundreds of feet per second. These eruptions can last for hours or even days. Hawaiian eruptions are not usually very explosive; instead, they produce streams of slow-moving lava. An interesting feature of Hawaiian eruptions are "fire fountains", huge fountains of magma being spewed into the air. These fountains last anywhere from a few minutes to a few hours.Strombolian eruptions put on an impressive display but are not usually very dangerous. During these eruptions, lava is shot fifty to a few hundred feet into the air and is accompanied by booming noises. These eruptions do not produce much lava flow. Vulcanian eruptions do not have much lava flow either, but they tend to be larger than Strombolian ones. They produce a lot of ash and spit out "bombs" of hard pyroclastic material. Hydrovolcanic eruptions occur when water vapor hits hot magma and gases, and forms huge steam clouds that rise from the volcano. Fissure eruptions occur when magma leaks up

through a long crack in the ground. They are associated with "curtains of fire" - magma being spewed up to a small height all along a fissure.

There are also different shapes and sizes of volcanoes. Stratovolcanos are usually very high, with pointy tops. They are formed by repeated explosions, usually Plinian, and by slow-moving lava. Eruptions from these volcanoes are usually very large but occur infrequently. Mount Vesuvius, which buried the Roman city of Pompeii in 79 AD, is a stratovolcano. Shield-type volcanoes are usually spread out over a large area and have gently sloping sides. They are caused by minor explosions (usually Hawaiian) and erupt more frequently than stratovolcanoes. Most of the major volcanoes in Hawaii are shield volcanoes. Scoria Cones are the most common volcano type, usually caused by Strombolian eruptions. They are shaped like upside-down cones, with slightly squished tops. Scoria cones usually erupt only once.

Introduction to Volcanism

Volcanoes are one of the most dynamic, powerful, and visible forces on Earth. What are volcanoes and what factors cause them to form in certain areas? How are geothermal features like fumaroles and geysers related to these temperamental mountains?

Let us start by looking at the volcano itself and learn the different parts of it, the rocks associated with it, and where volcanoes form.

 

What is a Volcano?

Hot magma, melted rock below Earth's crust, rises and collects in a magma chamber deep below the surface. If the magma flows through a conduit up to a vent on the surface, then it may cause an eruption and form a volcano.

Gases, lava, and pyroclastic material are erupted from volcanic vents. The mountain that forms from layers of lava and tephra is called a volcano. The word "volcano" comes from the name of a

Roman god, Vulcan, who was the god of fire. Magma that solidifies inside a volcano can form dikes and sills.

Volcanoes are classified as active, dormant or extinct.

The Magma Chamber

Magma is the name given to melted liquid rock below Earth's surface. It is stored below the volcano in a chamber or reservoir. During active periods, this reservoir fills with magma. After a large eruption, or during dormancy, this reservoir can drain, which may trigger the creation of a caldera.

The Magma Conduit

The magma conduit is the plumbing system of the volcano. Molten magma creates “pipes”, through the volcano. Magma then travels through them to the surface.

The Main Vent

The main vent often is located at or near the summit of the volcano. This is where most eruptive activity (lava flows, pyroclastic flows, and large gas emissions) occurs.

Lava Flows

Lava flows occur during some eruptions. Once magma reaches the vent and flows onto the surface of Earth it is called lava. Lava flows add land to the surface, and build the mountains we call volcanoes. The island of Hawaii is nearly 100% cooled and solidified lava!

Pyroclastic Flows

Pyroclastic flows occur during some eruptions. These are super-heated clouds of volcanic material ranging from ash to volcanic bombs. Pyroclastic flows travel very fast, and can destroy everything in their path.

The Volcano

Volcanoes are built from layers of lava and tephra (particles of rock, solidified lava, and ash of all different sizes). The lava cools on the sides of the volcano and hardens into rock. Pyroclastic flows and eruption clouds deposit tephra on top of lava layers, increasing the size of the mountain.

Dikes and Sills

The molten, pressurized magma intrudes into the solid volcanic rock to create dikes and sills. Dikes cut across volcanic rock layers, and sills run parallel to the layers. Eventually the magma hardens inside Earth and becomes an intrusive igneous rock.

Vulcan, Roman God of Fire

In Roman mythology, Vulcan was the god of fire. He was also known as the blacksmith of the gods.

There is a small volcanic island in the Mediterranean Sea called Vulcano. The local residents once believed the volcano on the island was the chimney of Vulcan's workshop. They thought the hot lava and smoke issuing from the mountain were products of Vulcan's work as he created thunderbolts for Jupiter, king of the gods, and weapons for Mars, god of war.

Active, Dormant, and Extinct

Volcanologists classify volcanoes based on how much activity has been recorded over time.

Active

An active volcano is currently erupting or has erupted in recent history. Active volcanoes can have eruptions of gases, pyroclastic material, tephra, and lava.

Dormant

A dormant volcano is not presently erupting, and has not erupted in recent history. There is still potential for renewed activity, because there still may be magma moving or cooling deep inside the volcano.

Extinct

An extinct volcano has not erupted in recent history and is unlikely to erupt again. Wind and water have broken and smoothed the shape of the mountain. The magma has drained below the surface or cooled inside the volcano.

 

Magma

Magma is the word used to describe melted or molten rock inside Earth. Magma is composed of elements, minerals, and gases that were present in the rock before it melted.

The major elements in magma are those present in Earth's crust: oxygen (O), silicon (Si), aluminum (Al), iron (Fe), calcium (Ca), sodium (Na), magnesium (Mg), and potassium (K). These elements combine to form minerals such as magnetite, hauynite, olivine, pyroxene, hornblende, plagioclase, potassium feldspar (k-feldspar), and quartz.

Magma also contains dissolved gases like water vapor (H2O), carbon dioxide (CO2), and sulfur dioxide (SO2).

More on Magma

The composition of the magma determines the eruption style, rock type, and volcano shape. Variations in the chemical compositions and properties of the magma determine whether it will be classified as mafic, felsic, or intermediate.

Mafic

- High melting point, pH, density, and Mg and Fe content- Low viscosity- Form basanite and basalt rocks- Typically effusive eruptions- Form shield volcanoes, flood basalts, cinder cones, and fissure eruptions

Intermediate

- Intermediate melting point, viscosity, pH, density and mineral composition- Form andesite rocks- Typically explosive eruptions- Commonly form composite volcanoes

Felsic

- Low melting point, pH, and density- High viscosity and Si content- Form rhyolite rocks- Typically very explosive eruptions- Form composite volcanoes, lava domes, and calderas

 

Types of Volcanoes

Volcanoes are openings, or vents, in the surface of Earth where gases, lava and pyroclastic material are erupted. Because of the different types of magma, and the locations where they form, volcanoes can have a wide variety of shapes and sizes.

Volcanoes are classified based on their height, shape, magma type, and eruption style. In this section, you can learn about four types of volcanoes.

The two primary types are shield volcanoes and composite volcanoes. Cinder cones and lava domes are considered to be secondary cones, because they occur on or near composite or shield volcanoes.

Shield Volcanoes

Shield volcanoes have the shape of a warrior's shield lying flat on the ground: very broad with large bases. This is due to the low viscosity of the magma. They are not as steep as composite volcanoes, but are often greater in volume.

Shield volcanoes usually have slow, gentle eruptions that produce large volumes of mafic magma (rich in iron and magnesium). Although these eruptions are usually relatively quiet, there can be large explosions when magma comes into contact with groundwater, vaporizing the water instantly. Shield volcanoes are found commonly in oceanic areas, such as Hawaii. The Big Island of Hawaii is made up of five huge shield volcanoes.

How Shield Volcanoes Form

Explore the steps involved in the formation and growth of a shield volcano.

Initial Vent Formation

A magma reservoir sits below the ocean floor. Pressure builds, pushing the magma closer and closer to the surface. Small vents and fissures open on the ocean floor, and lava escapes. Pillow lavas form when the molten rock comes in contact with the cold seawater.

Shield Building

Many successive lava flows, over thousands or even millions of years build a mountain that is shaped like a warrior's shield. Eruptions happen often, and large amounts of lava are poured out of the vent, so the mountains can grow to immense proportions.

Lava Fountains

Shield volcano eruptions are commonly gentle and effusive, with great quantities of basaltic lava flowing out of the vent. Mafic magma has low viscosity and flows easily, so lava from a shield volcano can flow great distances. Sometimes spectacular lava fountains occur when molten rock is squirted thousands of feet in the air above an erupting vent.

Eruptions and Intrusions

Magma rising from a sea-floor vent can come to the surface to cause an eruption at the main vent or at a fissure or smaller vent on the flank of the volcano. Magma can also create intrusive igneous structures like dikes and sills.

Caldera Formation

After an eruption all of the magma has either been expelled through the vents, or has drained back into a reservoir deep below the volcano. The conduits through which it flowed are left hollow and empty. Because of the heavy weight of hardened lava over the unstable, empty magma conduits, the summit of the volcano can collapse, forming a huge crater known as a caldera.

Erosion and Reef Building

Erosion from the wind and waves carves away at the volcano's summit and flanks. The volcano's height is reduced as it is eroded from the top, and the weight of the layers and layers of lava causes the volcano to subside (sink). Sandy sediments build up, and coral reefs begin to grow in the shallow water. As water depth increases, the coral die from lack of sunlight. New reefs can grow on top of the deeper ones.

Atoll Formation

Continued erosion and subsidence (sinking) of the volcano reduce its height to sea level or below. Coral reefs keep growing, building on each other in the shallow water. The reefs eventually form an atoll, which is a group of islands in the shape of a ring with a lagoon in the middle.

Seamount Formation

Eventually the volcano sinks faster than the reefs are growing. Below sea level wave erosion flattens the top of the volcano, which is now called a seamount.

Shield Volcanoes in National Parks

Explore some of America's national parks where shield volcanoes can be found.

Hawaii Volcanoes National ParkWrangell-St. Elias National Park and Preserve

Composite Volcanoes

Composite volcanoes are also called stratovolcanoes because they are made from many layers (strata) of rock, ash, and hardened lava. In addition, volcanic mudflows (lahars) can make up some of the layers.

Composite volcanoes experience very explosive eruptions because of the intermediate to felsic magma types (high viscosity, high silica, low melting temperature). Composite volcanoes are steeper near the summit, but slope more gently near the base of the mountain. Composite volcanoes are typically found on island arcs and continents at subduction zones.

How Composite Volcanoes Form

Explore the steps involved in the formation and growth of a composite volcano.

Magma Reservoir

A magma reservoir sits below the ground in Earth's crust. Composite volcanoes form in areas where subduction occurs. Subduction happens when tectonic plates collide and one plate is pushed below the other into the interior of Earth.

The magma creating composite volcanoes is likely to have a high content of silica, making it explosive. As the volume of magma in the reservoir increases, pressure builds until a vent opens in the ground and a volcano is formed.

Lava Layers

Composite volcanoes are also called stratovolcanoes because they are composed of layers (strata) of lava flows, tephra, and mudflows.

Lava, magma that has reached Earth's surface, pours out of the main vent at the summit of the volcano, flows down its sides and hardens to form a steep mountain.

Tephra Layers

Composite volcano eruptions do not always involve lava. Some eruptions release pressurized volcanic gases in great explosions that expel tephra (ash, lapilli, cinders, bombs) into the air. This material can fall back onto the volcano, adding another layer to its height and width.

Continued Layering

Eruptions of lava flows and pyroclastic material continue, building a mountain that will be thousands of feet high. Typically, composite volcanoes erupt andesite-based lava, but they can contain lava of any composition from basalt to rhyolite.

Continued Layering

Composite volcanoes are usually active over hundreds of thousands of years. During this time, there are many eruptions with periods of dormancy between them. Generally, lava flows and pyroclastic deposits do not occur in the same eruption. The volcanoes grow to great heights, typically having a gentle slope at the base, and a steeper slope at the summit.

Explosive Eruptions

Composite volcanoes frequently erupt explosively. Magma can push its way inside the volcano to form dikes and sills, or flow out of a vent. Composite volcanoes can have multiple vents, at the summit and on the flanks of the mountain. Lahars (volcanic mudflows) can course down the side of the volcano, and hot pyroclastic flows rush downslope carrying gases, tephra, and debris at high speeds and temperatures.

Caldera Formation

During an eruption, the magma and gases that were creating high pressures inside the volcano are released. This leaves the top of the mountain very unstable. This instability can cause the summit of the volcano to collapse in on itself, forming a caldera.

Lava Dome Formation

Renewed volcanism in the caldera can lead to the formation of lava domes in the caldera. Lava domes form when viscous lava pours out of the vent. Volcanic gas and steam are still released from the caldera as the magma and pyroclastic material cool.

Erosion

After many thousands or millions of years, the summit and flanks of the dormant volcano are eroded and smoothed. The layers of the volcano that were formed from tephra and mudslides erode more easily than the layers formed from lava flows. Erosion can also expose intrusive igneous rocks like dikes and sills that formed inside the volcano's layers.

Composite Volcanoes in National Parks

Explore some of America's national parks where composite volcanoes can be found.

Aniakchak National Monument and PreserveKatmai National Park and PreserveLake Clark National Park and PreserveMount Rainier National ParkNorth Cascades National Park

Cinder Cones

Cinder cones are considered secondary cones because they generally form in areas of other volcanic activity, including on composite and shield volcanoes. Cinder cones are peaks formed when pyroclastic materials are ejected into the air from a vent and fall back to the ground around the vent in a cone-shaped pile resembling a mound of cinders.

The cones are small, steep-sided, and symmetrical. These volcanoes can form individually over a vent. They can also form in the crater or on the flank of another larger volcano. Wizard Island in Crater Lake National Park in Oregon formed after the summit of Mount Mazama collapsed.

How Cinder Cones Form

Explore the steps involved in the formation and growth of a cinder cone.

Vent Formation

Below the ground a magma reservoir forms. It grows in size until the pressure is too great and vents form in the crust. Cinder cones are the most common volcano, and are often found in clusters of up to 100 cones. They can align along fissures, or be parasitic cones on the flanks of a composite or shield volcano.

Cone Formation

Cinder cones typically erupt only once. The magma in the vent contains vesicles (gas bubbles) that cause lava to be thrown up into the air, where it cools and hardens before it falls back to the ground around the vent. These solid lava fragments are called cinders. They pile up in the shape of a cone around the vent.

Lava Flows

Cinder cone eruptions can also include lava flows. Rather than create a conduit through the porous, weak pile of cinders, the lava flows out at the base of the cone, from a vent called a "boca." "Boca" is Spanish for "mouth."

Endangered Volcanoes

Cinder cones can grow to be about 600 to 900 feet tall. The shortest eruptions last less than a month and the longest over 10 years. People mine cinder cones, sometimes destroying them, because the cinders can be used for road construction, road sanding in winters, and decorative "lava rocks" for grills and landscaping.

Cinder Cones in National Parks

Explore some of America's national parks where cinder cones can be found.

Sunset Crater Volcano National MonumentCapulin Volcano National Monument

Lava Domes

Lava domes, like cinder cones, are considered secondary cones. They form when magma below the surface has great upward pressure. This pressure causes the most viscous magmas to move toward the surface, forming steep-sided and bulging mountains. The domes are commonly composed of felsic magma, but can also be intermediate.

The domes grow slowly, but can be responsible for highly explosive eruptions. Lava domes can contribute significantly to the formation of composite volcanoes, and are often built at or near the summit of composite volcanoes.

How Lava Domes Form

Select the following numbers to explore the diagram and see the steps involved in the formation and growth of a lava dome.

Lava

Lava domes are formed from pasty, high-viscosity magma with dacite or rhyolite composition. Lava domes occur in the summit craters of composite volcanoes, as parasitic domes on the flanks of composite volcanoes, or as volcanoes with their own vent.

Dome Building 1

The dacite or rhyolite magma is too viscous to form a lava flow. Instead, it extrudes slowly out of the vent, piling into a dome.

Dome Building 2

Most lava domes are small compared to other types of volcanoes. The domes do not usually have craters.

Dome Building 3

The high-silica, viscous magma is injected into the dome, pushing it up and out in layers. Sometimes this increasing pressure on the hardened lava layers of the dome causes a collapse. The collapse of a lava dome can lead to pyroclastic flows.

Eruption

Lava domes themselves do not typically erupt explosively, but the domes forming in the summit craters of composite volcanoes can be destroyed when the composite volcano erupts. These

highly explosive and violent eruptions calm down as the volatile gases escape from the magma. The viscous magma that is left can begin to form another dome.

Successive Domes

Lava domes can be built fairly quickly, as fast as a few days, or longer. Explosive eruptions or collapses can destroy them even faster. In an active area for dome building, new domes begin to form shortly after old ones are destroyed.

Lava Domes in National Parks

Explore some of America's national parks where lava domes can be found.

Aniakchak National Monument and PreserveLake Clark National Park and Preserve

 

Volcanic Rocks

The Latin word igneous means "fire-formed." Igneous rocks are formed when molten rock cools and hardens. There are two classes of igneous rocks - extrusive and intrusive.

Extrusive igneous rocks are created when lava and/or pyroclastic materials cool at or above Earth's surface (Earth's exterior). Extrusive rocks are also called volcanic rocks.

Intrusive igneous rocks are formed when magma cools and solidifies below the surface of Earth (Earth's interior). Intrusive rocks are also called plutons. The majority of Earth's igneous rocks are plutons.

The cooling history and the chemistry of the magma will determine what kind of igneous rock will form, and how that rock will look when it is completely cooled. When magma cools slowly, there is time for crystals and grains to form in the rock. This gives the rock a coarse texture, and leaves visible crystals on it's surface. When magma cools rapidly, there is no time for crystals to form, and the rock has a very fine texture. Other rocks may have a more complicated texture, where the parts that cooled fast are fine, and the parts that cooled slower are coarser.

Extrusive Igneous Rocks

Extrusive igneous rocks, also known as volcanic rocks, are the result of lava and pyroclastic material cooling at or on the surface of Earth. Volcanic rocks can be found in a wide range of sizes, shapes, colors, and textures.

Volcanic rocks range from black to white in color. Rocks that cool quickly can have textures as fine as glass. Obsidian, volcanic glass, is a smooth, shiny rock that forms when basaltic lava

cools quickly. The most common types of volcanic rocks are basalt, andesite, dacite and rhyolite. Click on the rock images to learn more about each type.

Dacite

Dacite is usually light gray, but can be darker gray or black. They have a high concentration of visible crystals. Lava domes are commonly made from this rock, which is formed from intermediate magma.

Rhyolite

Rhyolite rock is light colored. Rhyolite forms from felsic magma, which can cause explosive eruptions. The rocks formed will look different depending on the type of eruption they were ejected by.

Andesite

Andesite rock is gray to black in color, with visible crystals. It is formed from intermediate magma, which can be erupted explosively.

Basalt

Basalt rock is formed from mafic magma. It is usually very hard and dark gray or black in color. The islands of Hawaii are made almost entirely of basaltic lava flows.

Intrusive Igneous Rocks

Intrusive igneous rocks are formed when magma cools below Earth's surface. The magma is insulated underground, which allows it to cool slowly. The rocks that form from the magma are generally coarse-grained and have visible crystals.

Intrusive igneous rocks, regardless of their size or shape, are called plutons. Magma usually comes up from deep inside Earth and pushes its way into softer layers of sedimentary rock. The magma cools, and igneous rock formations are left inside the sedimentary rock layers. Igneous rocks are harder and resist weathering better than sedimentary rocks, so erosion eventually uncovers the intrusive igneous rock features.

Batholith

The largest pluton, which has a surface area of 100 square kilometers or more. Batholiths form over long periods of time and can have irregular shapes. Many mountain ranges are batholiths that have been exposed by erosion over time.

Stock

A pluton that has a surface area less than 100 square kilometers. Stocks are similar to batholiths because they form over long periods of time, and can have similar shapes, but stocks are smaller.

Dikes

Intrusions of magma that cut through sedimentary rock layers.

Sedimentary Rock Layers

Often present at the top of Earth's crust. Magma from deep below pushes through these layers. Solidified magma is harder than sedimentary rock, so when the surrounding sedimentary rock is eroded, underlying igneous rocks are exposed.

Laccolith

Mushroom-shaped bulges that form on sills. The bulge pushes the rock layers up above it.

Sills

Intrusions that run between or parallel to layers of sedimentary rock.

 

Where Volcanoes Form

There are three places that volcanism commonly occurs. These are at hot spots, spreading centers and fault zones, and subduction zones.

Hot Spots

Volcanic activity can occur in areas that are in the interior of a plate, far away from spreading centers or subduction zones. Rising magma somewhere inside the borders of a plate can create a local "hot spot." There are between 50 and 100 hot spots identified around the world, and they occur in both continental and oceanic plates.

Hot spots originate deep inside Earth, so they remain stationary while the plates above them move. That is how island chains like the Hawaiian Islands are formed. The magma associated with hot spots is mafic, so shield volcanoes are commonly formed. Hot spots are also associated with many geothermal features.

The Hawaiian Islands were formed when the Pacific Plate passed over a hot spot. Yellowstone National Park is also a result of hot spot volcanism.

Hawaii Volcanoes National Park, HawaiiHaleakala National Park, HawaiiYellowstone National Park, Wyoming, Idaho, and Montana

Spreading Centers and Fault Zones

Spreading centers are places where tectonic plates are diverging (moving away from one another). As the plates separate, a pathway is created for magma to move toward the surface. Spreading centers can extend into continental plates, such as The Great Rift Valley in East Africa. Magma produced at spreading centers is mafic. Therefore, much of the oceanic crust is made of basalt, a mafic rock.

Some of the magma produced at spreading centers erupts as lava flows and pyroclastic material, but most of it cools internally below Earth's crust. Fault zones are areas where the crust is cracking, usually due to the movement of the tectonic plates. Earthquakes and volcanism are common around fault zones.

There are no areas of active sea-floor spreading found within a national park of the United States. The country of Iceland, however, continues to grow due to the phenomenon. There are a few national parks that have evidence of past volcanism in rift valleys.

Petroglyph National Monument

Subduction Zones

Subduction occurs when two tectonic plates converge, and the denser of the two plates is pushed beneath the other plate. Volcanism will be present at the leading edge of the top plate. When a continental plate and oceanic plate converge, the denser oceanic plate is subducted.

The descending plate is heated by pressure and Earth's geothermal gradient. This leads to the formation of magma. The magma rises to the surface, and a belt of composite volcanoes forms. Subduction commonly generates felsic and intermediate magmas. There is not much volcanic activity at the convergence of two continental plates because continental crust is typically not dense enough to be subducted.

The volcanic activity on the Aleutian Islands and the Alaskan Peninsula is caused by subduction. The denser Pacific Plate is being subducted below the North American Plate. Visit volcanic parks in Alaska that are associated with subduction zones.

Aniakchak National Monument and PreserveLake Clark National Park and PreserveKatmai National Park and PreserveWrangell-St. Elias National Park and Preserve

Concept of Volcanoes

 A volcano is a vent or an opening on the surface of the earth’s crust that allows hot magma, volcanic ashes and gases to escape from below the earth’s surface.

Volcanoes are mostly found where the tectonic plates are diverging or converging. Tectonic plates are nothing but the large scale motion of earth’s lithosphere.

Volcanoes can also form at places where the earth’s crust is thin and stretched.

Origin of name:

The word volcano has its origin from the little island of Vulcano in the Mediterranean Sea off Sicily. Centuries ago, people residing this area believed that Vulcano was the chimney of the forge of Vulcan (Lat. Volcanus)--the blacksmith of the Roman gods. 

Types of volcanoes:

Depending on the frequency of eruption of the volcanoes they are categorized as:  

o Active volcanoes: These are the ones that are still alive and erupt frequently. For example:

Barren Island in the Andaman sea. 

o  Dormant volcanoes: These are the ones that have erupted in historical times and are quiet

now. For example: Mauna Kea, one of the five volcanoes that make the big island of Hawaii. 

o Extinct volcanoes: According to the scientists the volcanoes that are unlikely to erupt again,

because the volcano no longer has a lava supply are termed as extinct volcano. For example: the volcanoes on the Hawaiian – Emperor seamount chain in the Pacific Ocean

Geologists however group volcanoes into four main kinds: 

o Cinder cones,  

o Composite volcanoes,  

o Shield volcanoes, and

o Lava domes.

Effect of volcanoes:

Volcanoes in the populated area pose a serious threat to human lives because volcanoes are often associated with earthquakes, hot springs etc which again causes havoc. Besides volcanoes are sources of large amount of gases. Water vapor is the most abundant volcanic gas, followed by carbon dioxide and  sulfur dioxide. Other gases include  hydrogen sulfide, hydrogen chloride, and  hydrogen fluoride.

A large number of minor and trace gases are also found in volcanic emissions, for example hydrogen,  carbon monoxide, halocarbons, organic compounds, and volatile metal chlorides.

Concept of Volcano

1. An opening in the Earth's crust from which lava, ash, and hot gases flow or are ejected during an eruption.2. A usually cone-shaped mountain formed by the materials issuing from such an opening. Volcanoes are usually associated with plate boundaries but can also occur within the interior areas of a tectonic plate. Their shape is directly related to the type of magma that flows from them—the more viscous the magma, the steeper the sides of the volcano. ♦ A volcano composed of gently sloping sheets of basaltic lava from successive volcanic eruptions is called a shield volcano. The lava flows associated with shield volcanos, such as Mauna Loa, on Hawaii, are very fluid. ♦ A volcano composed of steep, alternating layers of lava and pyroclastic materials, including ash, is called a stratovolcano. Stratovolcanos are associated with relatively viscous lava and with explosive eruptions. They are the most common form of large continental volcanos. Mount Vesuvius, Mount Fuji, and Mount St. Helens are stratovolcanos. Also calledcomposite volcano.

EXTRUSIVE IGNEOUS ACTIVITY How do Volcanoes Interact with Earth's Systems? Atmosphere- Earth's first atmosphere was created from gases released by volcanoes. Hydrosphere- Earth's water was likely produced by condensation of volcanic water vapor early in Earth’s history.

 Biosphere- Volcanoes have both positive and negative effects on the biosphere

Lava and its Properties Lava- The name we give to magma when it reaches Earth’s surface.  Lava can flow form from a volcano vent, the side of a volcano, or directly from the ground.

Some volcanic eruptions are slow and predictable, whereas some volcanic eruptions are explosive in nature.  The behavior of lava during eruption depends on: 1)  Amount of dissolved gases (water vapor, carbon dioxide, sulfur dioxide, hydrogen sulfide) in the magma . 2)  Viscosity (fluid’s resistance to flow) of the magma.  Viscosity depends on two factors: 

a) Silica (SiO2) content- Higher silica (more felsic) magmas are more viscous than low silica (more mafic) magmas.  The more viscous (more felsic) a magma is, the better it traps gas molecules and more explosive it is.

 b) Lava temperature- Cooler lavas are more viscous (trap gases better) than hot ones. 

Therefore, cool lavas tend to be more explosive than hot ones.  Which would tend to be cooling, felsic magmas or mafic magmas?  Which would be more explosive from a temperature point of view.

  

Pyroclastic Flows The most explosive eruptions can result in pyroclastic flows: fast moving mixtures of pyroclasts and gas. The solid material moves quickly down slope by floating on a layer of gas. Pyroclastic flows are the most deadly aspect of volcanic eruptions.

Parts of a Volcano Volcano- A topographically elevated body of extrusive rock that forms as lava and/or pyroclastic debris pile up over time. Vent - An opening through which lava erupts Crater - A basin-like depression over the vent at the summit of the volcano

 Caldera - A volcanic depression much larger than the original crater, having a diameter of at least 1 km (ex. Crater Lake in Oregon). A calderas will form if: a) The summit blows off, orb) The summit collapses into a vacated magma chamber. Other Eruptions of Lava Flood eruptions (flood basalts)Very fluid magma can seep out of the ground, forming horizontal layers of basalt of extremely large areas.These flood eruptions can create extensive lava plateaus (e.g., Columbia River Plateau and the Rio Grande Rift in New Mexico).In Siberia, extremely voluminous flood basalts coincide with Earth's largest mass extinction (the Permian extinction, 251 mya).

Submarine eruptionsNearly always basalticMid-ocean ridge eruptionsPillow structures indicate the lava flowed and solidified under water (common at mid-ocean ridge spreading centers).

Geophysical hazards: volcanic eruptions

Definition and characteristics 

Volcanic eruptions happen when lava and gas are discharged from a volcanic vent. The most common consequences of this are population movements as large numbers of people are often forced to flee the moving lava flow. Volcanic eruptions often cause temporary food shortages and volcanic ash landslides called Lahar. 

The most dangerous type of volcanic eruption is referred to as a 'glowing avalanche'. This is when freshly erupted magma forms hot pyroclastic flow which have temperatures of up to 1,200 degrees. The pyroclastic flow is formed from rock fragments following a volcanic explosion , the flow surges down the flanks of the volcano at speeds of up to several hundred kilometres per hour, to distances often up to 10km and occasionally as far as 40 km from the original disaster site.

The International Federation response adjusts to meet the needs of each specific circumstance. As population movement is often a consequence, the provision of safe areas, shelter, water, food and health supplies are primordial. In general response prioritizes temporary shelter materials;

safe water and basic sanitation; food supplies; and the short term provision of basic health services and supplies.

1. The definition of a volcano is a rupture in the Earth's crust where molten lava, hot ash, and gases from below the Earth’s crust escape into the air.

Types of Volcanos

a. Plate Volcanoes - The majority of volcanoes are formed when two of the Earth’s plates meet and collide. These volcanoes actually occur on the ocean floor.

If the amount of magma is significant enough, then the magma rises above the surface of the ocean. This is known as an island. When the two plates collide and one plate forces the other plate beneath it, a different reaction occurs.

If this happens, then the friction that is caused during this reaction makes the plate melt that is beneath the other plate. This then causes magma to rise up, and this creates a volcano. The volcanoes that form by this method are usually the most dangerous and the most volatile ones.

b. Shield Volcanoes - Shield volcanoes are extremely broad and flat when compared to other volcanoes.

Their shape is created by a significant amount of lava running down the surface of the volcano, and then cooling. The eruptions of shield volcanoes aren’t as severe as other volcanoes. When a shield volcano erupts, gases escape and the lava rise to the surface to gently flow down the sides of the volcano.

c. Composite Volcanoes - Composite volcanoes, also known as strato-volcanoes, are formed by alternate layers of rock fragments and lava. The shape of a composite volcano is large and cone-like.

d. Caldera Volcanoes - Caldera volcanoes are formed from considerable amounts of magma erupting from sub-surface magma chambers. When the magma erupts, it leaves an empty space below the surface. The eruption of a caldera volcano generally has the coolest lava; but, they are the most dangerous because their eruption might also cause tsunamis, large pyroclastic surges, and widespread falling of ash.

e. Decade Volcanoes - These volcanoes are sixteen volcanoes that have been identified by scientists as noteworthy due to their large eruptions, and their closeness to populated areas. They include: Avachinsky-Koryaksky in Russia, Nevado de Colima in Mexico, Mount Etna in Italy, Galeras in Colombia, Mauna Loa in the United States, Mount Merapa in Indonesia, Mount Nyiragongo in Africa, Mount Rainer in the United States, Sakurajima in Japan, Santa Maria in Guatemala, Santorini in Greece, Taal Volcano in the Philippines, Teide in Spain, Ulawun in New Britain, Mount Unzen in Japan, and Mount Vesuvius in Italy.

Facts About Volcanoes

f. Pressure builds in a volcano until the pressure must be expelled. The liquid and heat build up and force the lighter, melted rock buried deep below to the surface toward the surface of the Earth, causing an eruption.

g. Natural radioactive decay that occurs within the Earth causes a large amount of heat to be produced, which causes more rocks to melt into magma which travels towards the surface.

h. A high and low pressure disturbance cause the magma to rise to the surface and spill over the top.

i. Most eruptions occur when gas expands inside the Earth, reducing pressure and causing aggressive volcanic behavior.

j. Expelled magma on the surface of the Earth can take up to several hundred years to cool depending on its composition and location.

k. The molten lava that flows down the side of a volcano is composed of a mixture of gases, liquid rock, silica and crystals.

l. The rock element of the magma is categorized as either Rhyolite, Andesite, or Basalt.m. A major area of volcanic activity is called the "Ring of Fire" which extends around the

Pacific Plate from Alaska down both sides of the Pacific Ocean, around Australia and down to the Antarctic continent.

n. An example of a volcano is Mount St. Helens in Washington state in the U.S.o. An example of a volcano is the eruption of Krakatau in 1883 and the eruption of Mount

Tambora in 1815, the two largest explosive and destructive volcanoes since the 1800s.

Types of volcanoes

Interactive: Volcano map of New Zealand

Everyone knows what a volcano looks like – isn’t it a steep-sided cone with wisps of ash coming from the top, just like Rangitoto, White Island, Mt Ngāuruhoe or Mt Ruapehu? But what about small hills, peninsulas and lakes – are these volcanoes? Sometimes, yes they are – Banks Peninsula, Mt Eden and even Lake Rotorua are all volcanoes or the remnants of volcanoes.

Cone volcanoes

If you’re asked to picture a volcano, the steep-sided, cone-shaped volcano that immediately comes to mind is called a cone volcano. (It’s also sometimes called a stratovolcano or composite volcano.) Mt Taranaki and Mt Ruapehu are examples of cone volcanoes.

Mt Taranaki

A cone volcano is formed by magma forcing its way through the Earth’s surface (the crust) and, once erupted, the lavabuilds up near the vent. Over time, the lava and ash accumulate close to the vent area, building up until eventually a cone is formed.This cone shape requires a specific type of lava, often made up of andesite. The original magma is relatively thin and runny so it doesn’t explode with a massive explosion, showering the landscape for miles around. Instead, the lava flows like treacle down the side of the mountain, solidifying as it goes. This process eventually forms the steep-sided cone-shaped volcanoes such as Mt Ruapehu or Mt Taranaki.Shield volcanoes

Mt Eden

Shield volcanoes are formed from magma that is highlyviscous   and contains very little gas. Typically, such volcanoes spread the lava once erupted over wider areas and slowly build up plateaus, forming gentle sloped shield volcanoes.Rather than a pool of magma forcing through one vent to the surface, shield volcanoes are often formed from a largediffuse area of magma that forces its way through the crust at different points. This results in a large number of inactive volcanoes within a relatively small geographical region. Although each volcano isdormant, the field may remain active, and magma can push through and form another new volcano at another point.Shield volcanoes are associated with basalt magma which is hot, viscous and fast-flowing. The magma doesn’t erupt explosively, and the cone can form within a very small area (less than 5 square kilometres).Caldera volcanoes

Then, there are the really violent eruptions, throwing magma, ash and rock across large areas. These are the caldera volcanoes (sometimes called supervolcanoes). Following such a large eruption, the volcano collapses into the void left by the empty magma chamber and a large depression is formed.This type of eruption formed Lake Taupō and Lake Rotorua. Each lake was formed by water filling the crater that was left after an eruption.

Lake Rotorua

Caldera volcanoes are characterised by rhyolitic magma. This forms at relatively low temperatures (750–850ºC) and is thick. Gases like water vapour, sulphur dioxide and carbon dioxide are trapped until the magma reaches the vent and are suddenly released – a bit like shaking a can of fizzy drink then opening it. The resulting explosion sends ash (tephra) and rocks flying into the atmosphere.Caldera volcanoes can also generate pyroclastic flows – mixtures of hot dry rock fragments and gas that flow very rapidly and can travel for long distances over the land, sometimes at supersonic speeds.

Types of volcanic rock

Video: Differences in rocks

Rocks are not all the same. Some are heavy, some are light. Others are dark, while some can be almost pure white. Evenigneous rocks that are all formed from magma in the Earth’smantle can look very different.Igneous rocks

Rocks are broadly classified into three groups – igneous,sedimentary and metamorphic. Igneous rocks are formed from magma in the Earth’s mantle. They generally don’t contain fossils, don’t react with acids, don’t usually contain obvious layers, can be made of different minerals, sometimes have holes or bubbles and may be glassy in appearance. Volcanologists look for these igneous rocks so that they can learn more about where these rocks have come from and whether they were formed during a volcanic eruption.Geologists use the visual appearance of the rock as an initial clue to its composition but will then verify their ideas using specialised techniques. For example, scientists at The University of Auckland use an electron microprobe to measure the exact quantities ofsilica, iron, magnesium and many other chemicals that are in rock samples they collect. This information helps them to classify the rock and may give them direct clues about the volcano and the eruption that formed the rock.Lava solidifies to rock

New Zealand has 3 main types of volcanoes, and each has been formed from a different type of magma. Once the lava has erupted, it cools and solidifies into rock:

Basalt  magma often forms shield volcanoes. Andesite  magma often forms cone volcanoes. Rhyolite  magma often forms calderas. Depending on how much gas the magma contains, it can

also form cone volcanoes.

Basalt

Columnar basalt

The Earth’s crust is mainly basalt rock. It is a heavy, dark, grainy rock. Basalt is associated with great rock columns that are found in many places around the Earth, for example, the Organ Pipes in Dunedin or the Giant’s Causeway in Ireland.Basalt magma is formed at high temperatures (around 1,200ºC). When it comes out of the volcano, it is hot and liquid. It contains very little silica (less than 50%) and a lot of magnesium and iron, which makes the rock look dark.

The Auckland volcanic field has erupted this type of hot, runny iron-rich lava, and the landscape is dotted with mountains made from basalt and scoria (a red-coloured rock that contains large amounts of iron-rich minerals). Both rock types are excavated for building materials and landscaping.Andesite

Andesite

Andesites are lighter coloured than basalt because they contain less iron and more silica (50–60%). Some scoria rocks fall within the andesite classification because of their chemical composition.Magma that contains andesite is generally around 800–1,000ºC and forms steep-sided cone volcanoes (stratovolcanoes). Mount Ngāuruhoe is an example of an andesite volcano.

Rhyolite

Pumice

Rhyolite is light-coloured or white – this is a clue that the rock contains a lot of silica (more than 70%) and not much iron or magnesium.

Rhyolitic magmas are associated with low temperatures (750–850ºC) and are often thick, which means gases can’t escape. Some rhyolitic rocks are quite light, for example,pumice, which may still have evidence of the bubbles of gas trapped as the rock solidified.Magma on the move

The mantle layer

The high temperatures (900°C) and extremely high pressures that occur in the mantle layer of the Earth are enough to melt rock. The high pressure changes the rock into a viscous   semisolid called magma. It’s a bit like silly putty – still able to move but very thick in consistency – not the runny texture of golden syrup that is often imagined.This semisolid magma continues to move upwards through the crust, experiences less pressure and so becomes more fluid. The result is the lava we see erupting from active volcanoes.Getting through the crust

The superheated molten rock in the mantle doesn’t normally make it through the many kilometres of crust that forms the ground that we walk on. Only in certain areas where the crust is fractured or broken (called fissures) – like at the edge of a tectonic plateboundary – can the molten mantle start to creep through.The rock in the mantle is less dense than the crust that contains it so it will rise through any gaps. The molten magma is also hotter than the surrounding crust so it will begin to melt some of the solid rocks that surround it.Crusts and tectonic plates

Plate boundaries

The edges of tectonic plates form an ideal location for volcanoes to form. The crust here is already ‘broken’, and as a plate is subducted or forced under another, it melts in the hot mantle region to form more molten rock. This becomes a ready supply of new molten magma, which can result in more volcanoes. (Learn more about this in the article ‘Plate tectonics, volcanoes and earthquakes’.)

The explosion

Once the molten mantle rock forces its way through the crust, it eventually erupts through the volcano as lava. This lava cools and forms rocks that scientists study to try and tell them more about what is happening to cause volcanic eruptions and how the mantle is stored under a volcanic area. (Explore the different types of explosions that occur in the article ‘Types of volcanoes’.)

What triggers eruptions?

Scientists are currently working on finding out what triggers eruptions and what causes the magma to be released.

Current theories suggest that an upsurge of magma is related to the presence of gasesand water in the magma deep in the mantle that increase the pressure under hot spots and tectonic plate boundaries. Other scientists think that ‘earth tides’ may be important – these are twice daily deformations of the Earth’s surface caused by the moon, allowing the crust to weaken in places and allowing magma to rise.

Video: New models for volcanoes

One key to solving these questions is finding out how the mantle makes its way through to the surface. New research that is being done right here in New Zealand is looking at this question. For example, Professor Richard Price and his team are interested in how magma chambers are constructed and what cooled lava can tell us about processes that happen deep in the Earth’s crust. (Read about Richard’s work in the article ‘Exploring magma formation’.)

However, scientists are still searching for reliable ways to understand how volcanoes work and what causes them to erupt. A good understanding lies at the heart of predicting future eruptions and perhaps saving people’s lives. There are still important questions to be answered.

Volcanology methods

Video: Geology in the field

Scientists use a range of different methods to learn more about volcanoes. A volcanologist may start by conducting fieldwork, collecting rocks and samples, and then move into the lab to undertake detailed analysis. The combination of data from all this research will be combined to form a detailed picture of the volcano being studied.Fieldwork methods can include:

surveying

collecting rock samples

drilling core samples

seismic monitoring

gas monitoring

ground deformation monitoring.

Laboratory techniques can include:

electron microprobe radiocarbon dating potassium-argon dating.

Surveying

A volcanologist’s first job is to stop and look around. Nothing is collected or touched until they have made a full survey, which could include drawing the area. This provides a record of rock layers, the general landscape and where samples were collected. Volcanologists often use a notebook to make sketches and record data when they are in the field, and they also use laptop computers and digital cameras.

Collecting rock samples

The volcanologist’s standard tool is a rock hammer, which is used to chip off and collect samples from rocky outcrops. Volcanologists are looking for igneous rocks so that they can learn more about where these rocks have come from and whether they were formed during a volcanic eruption. These samples are analysed visually in the field and back in the laboratory to determine exactly what they are, what they are made of and how they may have been formed.Drilling core samples

As different events happen – volcanic eruptions, rain or sediments settling – layers of different rock can accumulate. Geologists can use this to tell more about when things happened and to date different events. Sometimes the rock the volcanologist is interested isn’t exposed, so they may need to drill deeper for samples. Hollow steel pipes, 2 metres long, are driven into the ground using large weights. The pipe fills with earth and rocks – this is called a ‘core sample’.

Each section of the core sample is recorded and numbered so scientists can reconstruct the layers in the right order back in the laboratory. A sample might be made up of different layers of ash (tephra), igneous rock and sedimentary rock, and there might be fossils or other material buried in the layers that offer further clues.Seismic monitoring

Seismometer

As magma rises through the crust towards the Earth’s surface, it can cause the crust to move and bulge. This movement or deformation can be detected by using seismographs, which measure the Earth’s movement, so they are an important tool for studying whether a volcano might erupt in the near future.Gas monitoring

If volcanologists suspect that a volcano is active or may be about to erupt, they can monitor the gases that are being released from the vent. These gases include water vapour, carbon dioxide and sulphur dioxide. As the magma rises to the surface, the composition of the gases being emitted can change, and volcanologists can use this information to predict how soon the volcano may erupt.Ground deformation monitoring

Scientists use satellites and GPS technology to see whether the ground is moving or deforming. This can be really important in a volcanic field such as Auckland where no two volcanoes occur in the same place. As magma rises from the field under the city, scientists may be able to see the bulges that are created in the Earth’s surface.Electron microprobe

Back in the laboratory, an electron microprobe allows scientists to measure the composition of small rock fragments that have been collected in the field – what minerals and crystals are present and how old they are. These measurements provide clues about the chemical composition of the volcanic material and allow scientists to identify the type of volcanic material and some information about the processes that helped to form them.Radiocarbon dating

Radiocarbon dating in volcanology is an indirect method of analysis as it cannot be used to date the rocks itself. Instead, it is commonly used to date fossils that are located in the rocks. Radiocarbon dating relies on the predictable decay of carbon atoms (from something that was once living) over time. Rocks contain no carbon, but volcanic explosions often trap material such as trees and leaves in the falling ash layer. These can look like chunks of charcoal in amongst the rock so it takes a trained eye to spot them. Radiocarbon dating can also be used to date the layers either side of the volcanic rock, such as sedimentary material that contains organic deposits.

Potassium-argon dating

Video: Measuring magma

Potassium-argon (K-Ar) dating is based on the same principle as carbon decay and can be used to date rocks directly. Volcanologists can measure the decay of potassium (K) to argon (Ar) that occurs over very long periods of time. One problem is that basalt rocks (the type commonly found in Auckland) are generally very low in potassium, so this technique is not always reliable.Putting the story together

With the combined information, volcanologists can start to develop an explanation. The clues give information about when a volcano erupted, what type of eruption it was and how much material was produced. Sometimes, this information is not complete and some of the clues may be missing, but over time, as more information is added, the explanation slowly becomes more convincing.

Our concept & philosophy

Our aim is simple: to give the people, that have been traveling with us, the feeling of wanting to come back, on another tour with VOLCANO DISCOVERY. In order to do so, we offer you professional, personalized first-class service to provide you the best possible volcano experience: 

small to extremely small international groups or individualsfirst-hand accurate knowledge from competent guides and trained geologists & volcanologistsflexible tour programsexclusive off-the-beaten-track programssafetyenviromental responsabilitylast but not least, the local flavor of each tour

A small and personal company, we specialize in tailor-made tours for small groups and individuals, that prefer quality service with a personal touch. Each tour is thoroughly researched,

carefully prepared and organized by one of our professional volcanologist team members - highly motivated and competent volcanologists or otherwise experts in their area.

Our understanding of exclusiveness is not simply defined by accommodation in 5-star hotels and transport by air-conditioned charter buses. On each trip, we try to provide our clients an intense experience of the cultural and culinary background of each destination.

Visiting active volcanoes can be physically demanding; getting to some of the most interesting locations can involve strenuous exertion and some physical discomfort. However, the unforgettable experience of visiting these wonderful sites is well worth the effort. The physical demands vary from tour to tour, but our programs are flexible enough to allow modifications to accommodate not only the group's interests and physical capabilities, but also weather changes, volcanic activity, and other external factors.

"Students should learn what causes earthquakes, volcanoes, and floods and how those events shape the surface of the earth. Students, however, may show more interest in the phenomena than in the role the phenomena play in sculpting the earth. So teachers should start with students’ immediate interest and work toward the science." (Benchmarks for Science Literacy p. 71.) 

For grades K-2, working with students’ immediate interests about the phenomena of erupting volcanoes is appropriate and probably the most meaningful way to introduce the topic of change. This lesson presents volcanoes through the making of volcano models. While students are constructing their physical representations of volcanoes, they will be filled with questions about volcanoes as well as how to build their models. This process will provide students with a tangible reference for learning about volcanoes and give them a chance to problem-solve as they build their models. 

Students will also be fascinated with the eruption aspect of volcanoes. In this lesson, students will be able to observe how the eruption changes the original form of their volcano model. In this way, students see first hand how this type of phenomenon creates physical change. While students at this level may struggle to understand larger and more abstract geographical concepts, they will work directly with material that will help them build a foundation for understanding concepts of phenomena that sculpt the earth. 

Many of the ideas in this lesson have been adapted from University of North Dakota'sVolcano

World website. To meet the needs and interests of your particular group of students, you can explore this site further to get additional creative ideas.

PLANNING AHEAD

It would be helpful to have a resource book available for students so they can refer to it themselves. 

It may also be helpful to prepare yourself by learning more about volcanoes. The following Web pages are good resources for your own background:

Volcano World Types of Volcanoes Lava Flows

It is suggested that you make your own volcano model in advance of doing this lesson with your students so that you can use your model to demonstrate an eruption.

MOTIVATION

Most students have not seen a volcano first hand. Many students at the K-2 level may be unfamiliar with what volcanoes are. A good place to start is to show students a photograph of a volcano. For an online still photograph, students can go to Current Volcanic Activity. Or, if you have other pictures of volcanoes, make these available to students. 

After students have seen photographs, you can talk with them about how volcanoes have "hot liquid" inside of them (if your students are ready, you can tell them that this is called magma). Sometimes this magma comes out of the volcano really fast (when the magma comes out, it is called lava). When this happens, we say the volcano is erupting. 

Visit the Ring of Fire site with your students. This site shows a short film clip of an actual volcano erupting. To view the video, click on "Video Clip" near the top of the page. This visual and auditory depiction will help students form an idea of what we mean by volcanoes and eruption. 

Students will also have fun physically playing out the concept of eruption. Have them crouch

down on the floor. Tell them that they are volcanoes. Inside they have hot liquid getting ready to come out. As the liquid begins to rise, their bodies begin to rise. Soon the lava comes out the top, very fast and strong. Have them act this out by standing and jumping up, with their hands extended to the sky, and making eruption sounds!

DEVELOPMENT

Tell students that they will now have a chance to make their own volcanoes. Before they begin, lead a discussion about what they already know about volcanoes and the questions they may have. 

Some helpful questions to facilitate this discussion might be:

If you were to touch a volcano, what do you think it would feel like? What sound do you think volcanoes make when they erupt? What do you want to know about volcanoes?

Go to Volcano Models to find many ideas for creating different types of volcanoes, including lists of necessary materials. You may want to choose a model that is appropriate for your group of students, or you can offer students the opportunity to vote on which model the class will make. Although the class as a whole will make more than one volcano, if everyone makes the same model, students will have more opportunities to compare and contrast as they work on this project. At this level, keeping the number of variables to a minimum is appropriate because it helps students focus on the questions you are posing. 

Have students work in small groups for this project. Working together will facilitate extended discussion about volcanoes. The students' questions and discussions with each other will help you know what kind of further information they are looking for about volcanoes, and their questions will shape the additional group discussions you will likely have in the classroom. 

Questions you might anticipate from students may be less about volcanoes themselves and more about how to make their models. This provides an excellent opportunity for problem-solving, both individually and among the group. Although the Building Volcano Models site suggests particular materials for making each volcano model, having other materials available for students supports their individual efforts to solve problems they may encounter while structuring their models. 

Once students have completed their volcanoes (but before they erupt), refer them to theVolcano 1 student sheet. Encourage students to draw pictures or write words that describe their

volcanoes. 

To help them document their observations, you might ask them: What does your volcano look like? What shape does your volcano have? What is the texture of its surface? Does your volcano look the same from every angle, or does it look different when you turn it

around?You can also provide students with string and ask them to measure their volcanoes, cutting the string to fit the size of their models. They can measure around the base of the volcanoes, as well as the height. You can ask, "When you measure your volcano with string, what do you find?" This will be a reference for them when they consider how their volcanoes may have changed after eruption. 

Now students will have fun watching their volcanoes erupt. (Some of the ideas listed on the site describe how to make the volcano erupt. If yours does not, the combination of baking soda and vinegar will give you an erupting effect.) 

Students may have difficulty thinking about particular observation questions during these eruptions because they will be so enthralled with the process of eruption. It is valuable for students to be involved with the eruptions in this way. Students will more easily be able to think critically about what they are seeing when they watch a volcano erupt a second time. So, if possible, videotape these eruptions or take before/after photographs. Then you can play the videotape of the eruptions (or show the before/after photos). Another alternative would be to create an eruption using a volcano that you made in advance. 

After watching their volcanoes erupt, you can ask students to look at the video/photos or watch yours erupt with particular questions in mind. For example:

Where is the "lava" coming out from? Where is the lava going? What do you hear as the lava is coming out? Have you seen anything like this before? What does it remind you of?

Students have now been challenged, both during the process of constructing their models and in class discussions, to think about many aspects of volcanoes. Just as you asked them at the outset of this project, you can ask them again, "What do you want to know about volcanoes?" Be sure to answer as many of their questions as possible, as well as provide suggestions for how they can find their own answers.

ASSESSMENT

The Volcano 2 student sheet will give students a place to document the changes they have been able to observe. To help them think about these changes, ask:

What does your volcano look like now? Is your volcano the same shape now that it has erupted? Touch your volcano. Does it feel different? In what ways? What made your volcano change? When you use your measurement string, what do you find now? Compare your volcano before it erupted to your volcano after it erupted. What is different? What

has changed?Refer students to the Volcano 2 student sheet and ask them to draw or write about the kinds of questions you have just discussed. It will be helpful for them to have their volcanoes in front of them as they do this. 

To encourage students to consider how their models helped them learn about volcanoes, lead a discussion that includes the following questions:

How do you think your volcanoes are like real volcanoes? How do you think they are different? When you made your volcanoes, what helped you know what they looked like? How could you have made your models better?

In a simple discussion, you can also look at some of the recommended children's books with students to help them connect the idea of physical, geographical change. Just as their volcanoes changed after eruption, so too do real volcanoes. This causes some change on the earth's surface. 

Consider asking your students to write a story or poem about volcanoes. 

Or, students may enjoy putting their volcano ideas to music with either words or simply with instruments. Dramatic play opportunities are creative ways for students to communicate their new-found volcano knowledge. 

These ideas offer students ways to reflect upon what they have learned. By writing a story or creating volcano music, or whatever the choice may be, students are challenged to think about how the pieces of their volcano project fit together to make a whole picture. They are also challenged to document in a new way, as well as to communicate their learning to others. These are important and meaningful science processing skills. This is excellent experience for the students and gives you an idea of what they learned from doing this project. 

At the end of this lesson, students should be able to:

Describe their volcano models and how they made them. Communicate their observations to another person. Understand how their models changed after eruption. Ask questions about volcanoes that indicate a higher level of understanding about them.

EXTENSIONS

Help students navigate Kids' Volcano Art Gallery. Here they will find volcano drawings done by other young students and have the option to submit their volcano drawing (from their student sheets) to this website. Students could also share their drawings with the rest of the class by giving a presentation or by helping to assemble a class volcano book.

Students may enjoy submitting not only their volcano drawings, but also a poem or story they wrote, or the photographs you took of their project to the Volcano World website.

Encourage students to create more volcano models with different materials. See Building Volcano Models for several ideas for constructing volcanoes. 

The following websites may be useful to you as you work with your particular group of students on ways to extend this project. Have fun!

Please Note: This page is for anyone interested in learning about the three general types of volcanoes.

Volcano Types: Shield, Composite, and Cinder Cone

Introduction: As a geology undergrad student atHumboldt State University, I learned some amazing and wonderful aspects about our planet. As a science teacher at Roseville High School, I would like to educate people on some of the mysterious ways our planet works. The following website will give viewers a basic understanding on the three general types of volcanoes: Shield, Composite Cone, and Cinder Cone.

Shield Volcanoes

For anyone who has ever visited, they may have witnessed the awesome power of shield volcanoes. Shield volcanoes are usually very large and are characterized by flat sloping sides. These flat sloping sides are the result of very runny, low viscosity (fluid) magma. The magma releases gases and therefore these volcanoes erupt quietly and non-explosively; which is why no casualties are observed when these volcanoes erupt. These volcanoes are made of layers of fluid basaltic magma. If you ever visit the Big Island of Hawaii, check out Volcano National Park, you won’t be disappointed.

Composite Cone Volcanoes

Composite (also known as Strato Cone volcanoes) are more common than shield volcanoes and have steeper sloping sides. Although they are smaller than Shield volcanoes, don’t let their size fool you—these volcanoes are extremely explosive and deadly when they erupt. Their explosive nature is the result of very thick, high viscosity magma which traps gases (kind of like opening a shaken can of soda). This thick rhyoititic/andesitic magma is also one of the reasons why these volcanoes have steeper sloping sides. When these volcanoes erupt, they explode with great force and send huge ash clouds into the air that blanket he surrounding area. These volcanoes are made of layers of ash and thick lava. Mt. Saint Helens in Washington and Mt. Fuji in Japan are two great examples of composite cone volcanoes.

Cinder Cone Volcanoes

Compared to the previous two volcanoes, cinder volcanoes are very small. Because of their small size, their eruptions are not considered to be hazardous and lethal. When these volcanoes erupt, they eject ash and cinder (hot small pieces of rock) into the air; therefore these volcanoes are made of layers of ash and cinder. Sunset Crater in Arizona and Paracutin Mexico are two perfect examples of cinder cone volcanoes.

I don't know where I'm a gonna go when the volcano blows

These words, suggested in a song by Jimmy Buffet in his 1979 Volcano album, probably reflect the concerns of many people living near active volcanoes. Volcanoes are beneficial to humans living on or near them. They produce fertile soil, and provide valuable minerals, water reservoirs, geothermal resources, and scenic beauty. But volcanoes can be very dangerous. Where can a person go to be safe from an erupting volcano? What types of volcanic hazards might they face? These questions are difficult to answer because there are many types of volcanic eruptions which produce different types of volcanic hazards.

Types of Volcanic Eruptions

When Mount St. Helens erupted on May 18, 1980, red hot lava did not spew out of the volcano and pour down its flanks. This perception of a volcanic eruption is a common one and is probably due in part to pictures seen on television or in books of the beautiful lava flows and lava fountains in Hawai'i. The type of eruptions in Hawai'i are known as hawaiian volcanism and are far less dangerous than the eruptions produced by Mount St. Helens. It is important to know what type of an eruption a volcano is most likely to produce so that the types of hazards produced by such an eruption can be identified. Knowledge of these types of hazards, will help determine where a person would need to go to be safe during a volcanic eruption.

Volcanic eruptions can be placed into two general categories: those that are explosive, such as at Mount St. Helens, and those that are effusive, such as in Hawai'i. The most active volcano in the world, Kilauea Volcano on the big island of Hawai'i, is generally a nonexplosive volcano (though there have been occasions when it erupted explosively). Eruptions from it normally result in gently flowing lava flows, spatter cones, and lava fountains. Another type of nonexplosive volcanism is flood basalts. Lava flows from this type of eruption are extruded from fissures and cover vast areas. These nonexplosive eruptions are the least dangerous type of volcanic eruption since people rarely get killed by them (Francis, 1993). However, they are devastating and may have global consequences.Many eruptions are explosive in nature. They produce fragmental rocks from erupting lava and surrounding country rock. Some eruptions are highly explosive and produce fine volcanic ash that rises many kilometers into the atmosphere in enormous eruption columns. Explosive activity also causes widespread ash fall, pyroclastic flows, debris avalanches, landslides, pyroclastic surges, and lahars. Explosivity is usually the result of gases expanding within a viscous lava. Another mechanism for explosions at volcanoes occurs when surface water or ground water enters a magma chamber. These eruptions are likely when a volcano occurs in a wet area or in the sea.

What is a Volcanic Hazard?

A volcanic hazard refers to any potentially dangerous volcanic process (e.g. lava flows, pyroclastic flows, ash). A volcanic risk is any potential loss or damage as a result of the volcanic hazard that might be incurred by persons, property, etc. or which negatively impacts the productive capacity/sustainability of a population. Risk not only includes the potential monetary and human losses, but also includes a population's vulnerability. The definitions of hazard and risk are not well-defined. For a more complete discussion of the definitions, please click here.Tilling and Lipman (1993) estimate that 500 million people will be at risk from volcanic hazards by the year 2000. In the past 500 years, over 200,000 people have lost their lives due to volcanic eruptions (Tilling, 1980). An average of 845 people died each year between 1900 and 1986 from volcanic hazards. The number of deaths for these years is far greater than the number of deaths for previous centuries (Tilling, 1991). The reason behind this increase is not due to increased volcanism, but due, instead, to an increase in the amount of people populating the flanks of active volcanoes and valley areas near those volcanoes (Tilling, 1991 and Hall, 1991).

Types of Volcanic Hazards

The following is a list of volcanic hazards. Click on the one that you are interested in learning about.

Volcanic Earthquakes Directed Blast Tephra Volcanic Gases Lava Flows Debris Avalanches, Landslides, and Tsunamis Pyroclastic Surge Pyroclastic Flows Lahars

Hazards Prevention

In recent years, with the eruptions of Mount St. Helens and Mount Pinatubo many advances have been made in the study of volcanoes particularily in eruption prediction. The problem with volcanoes is that, though there may be similarities between volcanoes, every volcano behaves differently and has its own set of hazards. That is why it's important for scientists to study and monitor volcanoes. Many active volcanoes near populated areas have not been sufficiently studied to assess risk.When scientists study volcanoes, they map past volcanic deposits and use satellites to look at volcanic features, ash clouds, and gas emissions. They also monitor seismic activity, ground deformation, and geomagnetic, gravimetric, and geoelectrical and thermal changes at a volcano. They study and monitor volcanic gases and monitor the temperature, flow rate, sediment transport, and water level of streams and lakes near the volcano.By studying volcanic deposits, scientists can produce hazard maps. These maps indicate the types of hazards that can be expected in a given area the next time a volcano erupts. Dating of these volcanic deposits helps determine how often an eruption may occur and the probability of an eruption each year. Monitoring of a volcano over long periods of time will indicate changes in the volcano before it erupts. These changes can help in predicting when an eruption may occur.

A Few Final Remarks...

The main reason scientists study and monitor volcanoes is so that those living near active volcanoes can be aware of the hazards produced by volcanoes. This awareness will hopefully prevent loss of life and property when an eruption occurs. It is important that scientists communicate with local government officials and the general public about hazards produced by the volcanoes in their area. This interaction and the developement of an emergency plan with established lines of communication will hopefully save lives and encourage better land use planning.

References Cited

Text by C.M. Riley, Augustine Volcano 1986 eruption photo courtesy of U.S. Geological Survey, Pu'u 'O'o photo by W.I. Rose, water buffalo in lahar photo by M.T. Dolan, MSH Dome photo courtesy of U.S. Geological Survey at CVO

4 Different Types of Volcanoes: Cinder Cones, Lava Domes, Shield and Composite Volcanoes

Learn the Different Types of Volcanoes.

Source:http://volcano.oregonstate.edu/sites/default/files...

Different Types of Volcanoes:

When we think of volcanoes, we often perceive the concept that we usually see in Hollywood movies

– hazardous, harmful, damaging and catastrophic volcanoes. Although that is pretty much the truth,

but actually there are many different types of volcanoes. Some of these volcanoes are actually very

dangerous, while others are not. In order to understand the true nature and catastrophic

characteristics of a volcano, it is important to know about the different types of volcanoes.

Generally, volcanologists divide volcanoes into 4 major types, which will be discussed later in this

article. For now, let us have a brief look atwhat is a volcano?

What is a Volcano?

Before we move forward to our main topic of discussion, which is the different types of volcanoes, it

is recommended to first understand that what is a volcano?

Definition of Volcano:

A simple explanation of what is a volcano can be understood by the following definition of volcano:

“A volcano is a vent that directly connects magma to the surface of the Earth.”

3 States of Volcanoes:

There are 3 states of volcanoes, which are important to understand to grasp the topic completely.

These 3 states of volcanoes are:

1. Extinct Volcanoes

2. Dormant Volcanoes

3. Active Volcanoes

Explanation of these 3 states of volcanoes is given below:

1. Extinct Volcanoes:

Extinct volcanoes are those volcanoes which have become dead or extinct. Extinct volcanoes are

declared extinct, and hence, they will never erupt again.

2. Dormant Volcanoes:

Like the name suggests, Dormant Volcanoes are those volcanoes that have been in the state of

sleep or dormancy for a very long period of time. Commonly, dormant volcanoes are those

volcanoes that have not erupted for at least 2,000 years ago. However, dormant volcanoes are not

extinct, and hence, can erupt at any stage of time.

3. Active Volcanoes:

Unlike Extinct Volcanoes and Dormant Volcanoes, Active Volcanoes are considered as immediate

threats. Active Volcanoes are those volcanoes that erupt lava, gases and/or show seismic activities.

An active volcano may have erupted recently, and is always at a risk of erupting again.

One of the most incredible videos.

Different Types of Volcanoes:

After understanding the above-mentioned basic concepts about the definition of volcanoes and the 3

different states of volcanoes, it is time to have a look at the 4 different types of volcanoes.

Geologists and professional volcanologists mainly classify four different types of volcanoes. This

classification of volcanoes is done on the basis of shapes, magnitude, structure and materials of

different volcanoes. Furthermore, the way these volcanoes erupt is also a major factor in this

classification.

Note: It should be noted that there numerous types of volcanoes – even more than four – but these

4 different types of volcanoes are the most basic ones.

A Cinder Cone Volcano

Source:http://www.kilaueaadventure.com/images/Kilauea-Puu...

1. Cinder Cones:

One of the most common types of volcanoes is the ‘Cinder Cones’. A relatively less-dangerous type

of volcano, Cinder cones only grow to about a 1,000 – 1,200 ft. Unlike some of the other types of

volcanoes – namely, shield volcanoes and composite volcanoes – these cinder cones are usually

created from a single opening. The opening of a cinder cone is a cone-shaped structure, while the

steeps are formed of the erupted, fragmented cinders that fall close to the chimney/vent.

The manner of eruption for cinder cones is relatively simpler. When the lava erupts, cinders of it are

blown into the air. It is these fragmented cinders that fall around its opening – which we talked about

earlier.

Some Famous Cinder Cones Volcanoes:

Paricutin in Mexico

Lava Bute

Sunset Crater

Mauna Loa is a famous shield volcano, located on the big island of Hawaii. It is also the world's largest active shield

volcano.

Source:http://img.timeinc.net/time/photoessays/2010/top10...

2. Shield Volcanoes:

Another type of volcanoes is the ‘Shield Volcanoes’. Unlike cinder cones, shield volcanoes can be

very, very big in size. However, they are not as much dangerous as it seems. This is because the

eruption of lava out of shield volcanoes is not accompanied by pyroclastic material. This makes the

eruption relatively safer and it keeps the shield volcanoes safe, too.

The structure of shield volcanoes can be understood as tall and broad, but with flat round shapes

around it. In comparison with some of the other types of volcanoes, shield volcanoes have low

slopes.

Because of their large structures, shield volcanoes can be huge. For example, Mauna Loa is a shield

volcano that is over 30,000 feet above sea level.

Some Famous Shield Volcanoes:

Hualalai

Mauna Loa

Kohala Volcano

A Famous Composite Volcano

Source:http://static.bbc.co.uk/earthscience/images/ic/640...

3. Composite Volcanoes:

Composite Volcanoes are also very commonly known as ‘Strato Volcanoes’. Composite volcanoes

are reasonably big and can rise up to 8,000 – 10,000 feet. Moreover, they can range anywhere

from 1 – 10 km in diameter. The nature of composite volcanoes’ eruption is dangerous and

explosive in nature. With a lot of layers of lava and pyroclastic materials involved, the eruption of

composite volcanoes is considered noticeably dangerous.

The general structure of composite volcanoes is tall, symmetrical shaped and with steep sides.

Commonly, composite volcanoes erupt numerous gases, ash, lava, pumice and also a small amount

of stiff. Moreover, deadly mudflows – also commonly known as ‘lahars’ – can also accompany the

eruption.

Because of their large quantity on the planet Earth and deadly mudflows, composite volcanoes are

believed to kill the most amounts of people and do serious damage to anything in their paths, when

compared with any other type of volcano. Apart from the scary side, some of the most beautiful

mountains on planet Earth are also, actually, composite volcanoes. For example, Mount Fuji of

Japan and Mount Shasta in California are some famous composite volcanoes.

An example of Lava Domes.

Source:http://upload.wikimedia.org/wikipedia/commons/thum...

4. Lava Domes:

Lava domes is the fourth type of volcano that we are going to discuss. Unlike composite and shield

volcanoes, lava domes are of significantly smaller stature. Basically, lava domes are formed when

the lava is too viscous to flow to a great distance, and hence, it continues to pile within. As the lava

dome keeps growing, the outer surface starts to cool and become hardened. When a lava dome is

grown to a significant extent, it shatters the outer surface, which results in spilling loose fragments

towards its sides. Generally, such lava domes are found on the flanks of larger composite

volcanoes.

Volcanoes

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Summary:

So, the bottom line is that there are four different types of volcanoes, i.e. composite volcanoes,

shield volcanoes, cinder cones and lava domes. Each with a different set of characteristics and

structure. Some are more dangerous and catastrophic, while others are comparatively lesser.

Having this knowledge keeps you informed about the different types of volcanoes.

How do volcanoes affect people?Category: 

 Volcanic Effects

 

Volcanoes affect people in many ways, some are good, some are not. Some of the bad ways are that houses, buildings, roads, and fields can get covered with ash. As long as you can get the ash off (especially if it is wet), your house may not collapse, but often the people leave because of the ash and are not around to continually clean off their roofs. If the ashfall is really heavy it can make it impossible to breathe.

Lava flows are almost always too slow to run over people, but they can certainly run over houses, roads, and any other structures.

Pyroclastic flows are mixtures of hot gas and ash, and they travel very quickly down the slopes of volcanoes. They are so hot and choking that if you are caught in one it will kill you. They are also so fast (100-200 km/hour) that you cannot out-run them. If a volcano that is known for producing pyroclastic flows is looking like it may erupt soon, the best thing is for you to leave before it does.

Some of the good ways that volcanoes affect people include producing spectacular scenery, and producing very rich soils for farming.

Gases

Water vapor, the most common gas released by volcanoes, causes few problems. Sulfur dioxide, carbon dioxide and hydrogen are released in smaller amounts. Carbon monoxide, hydrogen sulfide, and hydrogen fluoride are also released but typically less than 1 percent by volume.Gases pose the greatest hazard close to the vent where concentrations are greatest. Away from the vent the gases quickly become diluted by air. For most people even a brief visit to a vent is not a health hazard. However, it can be dangerous for people with respiratory problems.

The continuous eruption at Kilauea presents some new problems. Long term exposure to volcanic fumes may aggravate existing respiratory problems. It may also cause headaches and fatigue in regularly healthy people. The gases also limit visibility, especially on the leeward side of the island where they become trapped by atmospheric conditions.

Source of Information:  Volcanic and Seismic Hazards on the Island of Hawaii by Christina Heliker, 1991, U.S. Geological Survey General Interest Publication.

A deadly eruption

The 1815 explosive eruption of Tambora volcano in Indonesia and the subsequent caldera collapse produced 9.5 cubic miles (40 cubic kilometers) of ash. The eruption killed 10,000 people. An additional 80,000 people died from crop loss and famine.

Aircraft

To put it mildly, ash is bad for jet aircraft engines. Apparently the problem is much more severe for modern jet engines which burn hotter than the older ones. Parts of these engines operate at temperatures that are high enough to melt ash that is ingested. Essentially you end up with tiny blobs of lava inside the engine. This is then forced back into other parts where the temperatures are

lower and the stuff solidifies. As you can imagine this is pretty bad. One problem that I heard about is that pilots start losing power and apply the throttle, causing the engine to be even hotter and melt more ash.Added to this is the fact that ash is actually tiny particles of glass plus small mineral shards–pretty abrasive stuff. You can imagine that dumping a whole bunch of abrasive powder into a jet engine is not good for the engine. This has been a pretty non-scientific explanation of the problem. I just found an article that describes the problem a little more technically.

“The ash erodes sharp blades in the compressor, reducing its efficiency. The ash melts in the combustion chamber to form molten glass. The ash then solidifies on turbine blades, blocking air flow and causing the engine to stall.” This comes from the FAA Aviation Safety Journal, Vol. 2, No. 3.  

Safe distance

The distance you have to evacuate depends entirely on what kind of eruption is going on. For example, Pinatubo, one of the largest recent eruptions sent pyroclastic flows at least 18 km down its flanks, and pumice falls were hot and heavy even beyond that. For example, pumice 7 cm across fell at Clark Air base which is 25 km from the volcano! A 7 cm pumice won’t necessarily kill you but it does mean that there is a lot of pumice falling, and if you don’t get out and continuously sweep off your roof it may fall in and you’ll get squashed.On the other hand, the current eruption at Ruapehu is relatively small. In fact, there were skiers up on the slopes when the eruptions commenced, and even though they were only 1-2 km from the vent they managed to escape. The volcanologists routinely go up on the higher slopes of Ruapehu during these ongoing eruptions to collect ash and take photographs.

So you see, you need to know something about what you think the volcano is going to do before you decide how far to run away. I guess if you have no idea of what the volcano is planning, and have no idea of what it has done in the past, you might want to be at least 25-30 km away, make sure you have a good escape route to get even farther away if necessary, and by all means stay out of low-lying areas!

Cities and Towns

The effect an eruption will have on a nearby city could vary from none at all to catastrophic. For example, atmospheric conditions might carry ash away from the city or topography might direct lahars and pyroclastic flows to unpopulated areas. In contrast, under certain atmospheric, eruption and/or topographic conditions, lahars, pyroclastic flows, and/or ash fall could enter the city causing death and destruction.

This scenario brings up several interesting problems. How do you evacuate a large population if there is little warning before the eruption? Where do these people go? If an eruption is highly likely yet hasn’t happened yet how long can people be kept away from their homes and businesses?

I should point out that in most volcanic crises geologists advise local civil defense authorities. The civil defense authorities decide what to do concerning evacuations, etc.

The IAVCEI has a program to promote research on “Decade” Volcanoes. Decade volcanoes are likely to erupt in the near future and are near large population centers. Mount Rainier in Washington and Mauna Loa in Hawaii are two Decade volcanoes in the U.S. Other Decade volcanoes include Santa Maria, Stromboli, Pinatubo, and Unzen.

What happens to the towns around a volcano when it erupts depends on many things. It depends of the size and type of eruption and the size and location of the town. A few examples might help. The 1984 eruption of Mauna Loa in Hawaii sent lava towards Hilo but the eruption stopped before the flows reached the town. The 1973 eruption of Heimaey in Iceland buried much of the nearby town of Heimaey under lava and cinder. The 1960 eruption of Kilauea in Hawaii buried all of the nearby town of Kapoho under lava and cinder. In 1980, ash from Mount St. Helens fell on many towns in Washington and Oregon. The 1902 eruption of Mount Pelee on the island of Martinique destroyed the town of Saint Pierre with pyroclastic flows. In 1985, the town of Armero was partially buried by lahars generated on Ruiz. For more examples see Decker and Decker (1989).

Effects of volcanoes

Schematic of volcano injection of aerosols and gases.

Solar radiation graph 1958–2008, showing how the radiation is reduced after major volcanic eruptions.

Sulfur dioxide concentration over theSierra Negra Volcano, Galapagos Islandsduring an eruption in October 2005

There are many different types of volcanic eruptions and associated activity: phreatic eruptions(steam-

generated eruptions), explosive eruption of high-silica lava (e.g., rhyolite), effusive eruption of low-silica

lava (e.g., basalt), pyroclastic flows, lahars (debris flow) and carbon dioxide emission. All of these

activities can pose a hazard to humans. Earthquakes, hot springs, fumaroles, mud pots and geysers often

accompany volcanic activity.

The concentrations of different volcanic gases can vary considerably from one volcano to the next. Water

vapor is typically the most abundant volcanic gas, followed by carbon dioxide andsulfur dioxide. Other

principal volcanic gases include hydrogen sulfide, hydrogen chloride, andhydrogen fluoride. A large

number of minor and trace gases are also found in volcanic emissions, for example hydrogen, carbon

monoxide, halocarbons, organic compounds, and volatile metal chlorides.

Large, explosive volcanic eruptions inject water vapor (H2O), carbon dioxide (CO2), sulfur dioxide (SO2),

hydrogen chloride (HCl), hydrogen fluoride (HF) and ash (pulverized rock and pumice) into

the stratosphere to heights of 16–32 kilometres (10–20 mi) above the Earth's surface. The most

significant impacts from these injections come from the conversion of sulfur dioxide to sulfuric

acid (H2SO4), which condenses rapidly in the stratosphere to form fine sulfate aerosols. The aerosols

increase the Earth's albedo—its reflection of radiation from the Sun back into space – and thus cool the

Earth's lower atmosphere or troposphere; however, they also absorb heat radiated up from the Earth,

thereby warming the stratosphere. Several eruptions during the past century have caused a decline in the

average temperature at the Earth's surface of up to half a degree (Fahrenheit scale) for periods of one to

three years – sulfur dioxide from the eruption of Huaynaputina probably caused the Russian famine of

1601–1603.[15]

One proposed volcanic winter happened c. 70,000 years ago following the supereruption of Lake Toba on

Sumatra island in Indonesia.[16]According to the Toba catastrophe theory to which some anthropologists

and archeologists subscribe, it had global consequences,[17]killing most humans then alive and creating

a population bottleneck that affected the genetic inheritance of all humans today.[18] The 1815 eruption

of Mount Tambora created global climate anomalies that became known as the "Year Without a Summer"

because of the effect on North American and European weather.[19] Agricultural crops failed and livestock

died in much of the Northern Hemisphere, resulting in one of the worst famines of the 19th century.[20] The

freezing winter of 1740–41, which led to widespread famine in northern Europe, may also owe its origins

to a volcanic eruption.[21]

It has been suggested that volcanic activity caused or contributed to the End-Ordovician, Permian-

Triassic, Late Devonian mass extinctions, and possibly others. The massive eruptive event which formed

the Siberian Traps, one of the largest known volcanic events of the last 500 million years of Earth's

geological history, continued for a million years and is considered to be the likely cause of the "Great

Dying" about 250 million years ago,[22]which is estimated to have killed 90% of species existing at the

time.[23]

Ash plume rising from Eyjafjallajökull on April 17, 2010

The sulfate aerosols also promote complex chemical reactions on their surfaces that alter chlorine

and nitrogen chemical species in the stratosphere. This effect, together with increased

stratospheric chlorine levels from chlorofluorocarbon pollution, generates chlorine monoxide (ClO), which

destroys ozone (O3). As the aerosols grow and coagulate, they settle down into the upper troposphere

where they serve as nuclei for cirrus clouds and further modify the Earth's radiation balance. Most of the

hydrogen chloride (HCl) and hydrogen fluoride (HF) are dissolved in water droplets in the eruption cloud

and quickly fall to the ground as acid rain. The injected ash also falls rapidly from the stratosphere; most

of it is removed within several days to a few weeks. Finally, explosive volcanic eruptions release the

greenhouse gas carbon dioxide and thus provide a deep source of carbon for biogeochemical cycles.

Gas emissions from volcanoes are a natural contributor to acid rain. Volcanic activity releases about 130

to 230 teragrams (145 million to 255 million short tons) of carbon dioxide each year.[24] Volcanic eruptions

may inject aerosols into the Earth's atmosphere. Large injections may cause visual effects such as

unusually colorful sunsets and affect global climate mainly by cooling it. Volcanic eruptions also provide

the benefit of adding nutrients to soil through the weathering process of volcanic rocks. These fertile soils

assist the growth of plants and various crops. Volcanic eruptions can also create new islands, as the

magma cools and solidifies upon contact with the water.

Ash thrown into the air by eruptions can present a hazard to aircraft, especially jet aircraft where the

particles can be melted by the high operating temperature; the melted particles then adhere to

the turbine blades and alter their shape, disrupting the operation of the turbine. Dangerous encounters in

1982 after the eruption of Galunggung in Indonesia, and 1989 after the eruption of Mount Redoubt in

Alaska raised awareness of this phenomenon. Nine Volcanic Ash Advisory Centers were established by

the International Civil Aviation Organization to monitor ash clouds and advise pilots accordingly. The 2010

eruptions of Eyjafjallajökull caused major disruptions to air travel in Europe.

Volcanoes on other planetary bodies

The Tvashtar volcano erupts a plume 330 km (205 mi) above the surface ofJupiter's moon Io.

Olympus Mons (Latin, "Mount Olympus") is the tallest known mountain in our solar system, located on the planet Mars.

Main articles: Geology of the Moon, Volcanology of Mars, Volcanism on Io, and Volcanism on Venus

The Earth's Moon has no large volcanoes and no current volcanic activity, although recent evidence

suggests it may still possess a partially molten core.[25] However, the Moon does have many volcanic

features such as maria (the darker patches seen on the moon), rilles and domes.

The planet Venus has a surface that is 90% basalt, indicating that volcanism played a major role in

shaping its surface. The planet may have had a major global resurfacing event about 500 million years

ago,[26] from what scientists can tell from the density of impact craters on the surface. Lava flows are

widespread and forms of volcanism not present on Earth occur as well. Changes in the planet's

atmosphere and observations of lightning have been attributed to ongoing volcanic eruptions, although

there is no confirmation of whether or not Venus is still volcanically active. However, radar sounding by

the Magellan probe revealed evidence for comparatively recent volcanic activity at Venus's highest

volcano Maat Mons, in the form of ash flows near the summit and on the northern flank.

There are several extinct volcanoes on Mars, four of which are vast shield volcanoes far bigger than any

on Earth. They include Arsia Mons, Ascraeus Mons, Hecates Tholus, Olympus Mons, and Pavonis Mons.

These volcanoes have been extinct for many millions of years,[27] but the European Mars

Express spacecraft has found evidence that volcanic activity may have occurred on Mars in the recent

past as well.[27]

Jupiter's moon Io is the most volcanically active object in the solar system because of tidal interaction with

Jupiter. It is covered with volcanoes that erupt sulfur, sulfur dioxide and silicate rock, and as a result, Io is

constantly being resurfaced. Its lavas are the hottest known anywhere in the solar system, with

temperatures exceeding 1,800 K (1,500 °C). In February 2001, the largest recorded volcanic eruptions in

the solar system occurred on Io.[28] Europa, the smallest of Jupiter's Galilean moons, also appears to have

an active volcanic system, except that its volcanic activity is entirely in the form of water, which freezes

into ice on the frigid surface. This process is known as cryovolcanism, and is apparently most common on

the moons of the outer planets of the solar system.

In 1989 the Voyager 2 spacecraft observed cryovolcanoes (ice volcanoes) on Triton, a moon of Neptune,

and in 2005 the Cassini–Huygens probe photographed fountains of frozen particles erupting from

Enceladus, a moon of Saturn.[29] The ejecta may be composed of water, liquid nitrogen, dust,

or methane compounds. Cassini–Huygens also found evidence of a methane-spewing cryovolcano on

the Saturnian moon Titan, which is believed to be a significant source of the methane found in its

atmosphere.[30] It is theorized that cryovolcanism may also be present on the Kuiper Belt Object Quaoar.

A 2010 study of the exoplanet COROT-7b, which was detected by transit in 2009, studied that tidal

heating from the host star very close to the planet and neighboring planets could generate intense

volcanic activity similar to Io.[31]

Traditional beliefs about volcanoes

Many ancient accounts ascribe volcanic eruptions to supernatural causes, such as the actions

of gods or demigods. To the ancient Greeks, volcanoes' capricious power could only be explained as acts

of the gods, while 16th/17th-century German astronomer Johannes Kepler believed they were ducts for

the Earth's tears.[32] One early idea counter to this was proposed by Jesuit Athanasius Kircher (1602–

1680), who witnessed eruptions of Mount Etna and Stromboli, then visited the crater of Vesuvius and

published his view of an Earth with a central fire connected to numerous others caused by the burning

of sulfur, bitumen and coal.

Various explanations were proposed for volcano behavior before the modern understanding of the

Earth's mantle structure as a semisolid material was developed. For decades after awareness that

compression and radioactive materials may be heat sources, their contributions were specifically

discounted. Volcanic action was often attributed to chemicalreactions and a thin layer of molten rock near

the surface.

A volcano is actually an opening or a fissure, in the Earth's crust, through which lava or molten rocks, ash and toxic gases present below the surface of Earth are discharged by a sudden, violent eruption. Sometimes, it can be a mountain-like structure with a bowl-shaped depression at the top, through which these substances are expelled. The term 'volcano' is derived from the name of the Roman God of fire, Vulcan.

Volcanic structures are usually formed at places where the tectonic plates are either converging or diverging. A stretching or thinning of the Earth's crust, can also lead to the formation of volcanoes. They are often classified into three types, on the basis of their frequency of eruptions, i.e. active, dormant and extinct. The active volcanoes are characterized by regular eruptions, while the dormant volcanoes are those that erupted in the past, but are silent now. On the other hand, an extinct volcano is the one that erupted in the remote past and is unlikely to erupt again.

Effects on the Environment

It has been known for a long time that volcanic eruptions affect the environment in various ways. Whether large or small, eruptions do affect the environment for a period of time, mostly because of the gases they spew out. Many gases, like sulfur dioxide, carbon dioxide, carbon monoxide, chlorine (as HCl gas), fluorine (as HF gas), hydrogen, helium and hydrogen sulfide (H2S) are released into the environment. Along with all these comes out a huge amount of water vapor. Their effects on the environment depend on many factors like the local climate pattern, the scale on which the eruption has taken place, and the layer of the atmosphere to which the gases have spread, etc.

► Sulfur dioxide spreads to the top of the atmosphere where it reflects the rays of the Sun, and thus leads to the cooling of the atmosphere. This has the effect of bringing down the average global temperature, for a period of one or two years. A famous example of this is the cooling of the surface temperature of the Earth brought about after the eruption of

Mount Pinatubo in Philippines.

► Sulfur dioxide reacts with other gases and particles in the atmosphere to form volcanic smog.

► Sulfur dioxide also causes acid rain, air pollution, and depletion of the ozone layer.

► Carbon dioxide absorbs the Sun's rays, thereby increasing surface temperature of the Earth.

► Carbon dioxide is a heavy gas and thus can get trapped in some low-lying areas called depressions. People who breathe CO2-laden air of such an area can succumb to death. CO2 can also accumulate in the soil.

► Hydrogen chloride (HCl), owing to its extremely acidic nature, contributes to acid rains after an eruption.

► The volcanic ash released into the atmosphere after an eruption spreads to hundreds of square miles. It blankets the atmosphere around the volcano, blocking the rays of the Sun from reaching the ground. It has been theorized that a very large volcano can cause a 'volcanic winter'.

Effects on Living Beings

Volcanic eruptions affect plants and animals in myriad ways. Moreover, these eruptions impact lives both directly (loss of life and property), and indirectly (local environmental changes).

► Volcanic ash blows out as minute particles. When it is inhaled, it can cause coughing and shortness of breath. People suffering from asthma, bronchitis, and emphysema are especially affected by it.

► Coarser particles from pyroclastic flow can be lethal. When inhaled,

they cause death by choking the lungs and causing burns.

► Exposure to ash also causes other symptoms like runny nose and sore throat.

► Extremely hot lava can swiftly kill plants and animals.

► Due to the reduced visibility resulting from ash, accidents often take place in the area around the eruption.

► People living in vicinity of an eruption are at risk of injury and even death by roof collapse. This is because ash particles continually get deposited on the roofs of the dwellings. If the weight increases beyond what a roof can endure, it buckles.

► Fine ash particles get in the eye and cause irritation, burning, and itching. The cornea, which is the exposed part of the eye, suffers abrasion and inflammation.

A volcanic eruption is a natural calamity which, besides causing loss of human life and property, can cause considerable environmental changes. Though we cannot prevent the occurrence of such eruptions, we can reduce their devastating effects. Movement of magma, changes in the quantity and quality of gases emitted by the volcanoes and small earthquakes can serve as signals of volcanic eruptions. So, proper monitoring of these signals, ready disaster management techniques, and creating awareness among the general public about the hazards of volcanic eruptions can play an important role in minimizing the losses that occurs during such an disaster.

Negative Effects 

Volcanoes affect people in many ways, some are good, some are not. Some of the bad ways are that

houses, buildings, roads, and fields can get covered with ash. As long as you can get the ash off

(especially if it is wet), your house may not collapse, but often the people leave because of the ash and

are not around to continually clean off their roofs. If the ashfall is really heavy it can make it impossible to

breathe. 

Positive Effects 

Some of the good ways that volcanoes affect people include producing spectacular scenery, and

producing very rich soils for farming. Volcanic eruptions create economic mineral deposits. All this often

generates tourism. These results can greatly boosts a settlement's economy. 

The main good effect that volcanoes have on the environment is to provide nutrients to the surrounding

soil. Volcanic ash oftenb contains minerals that are beneficial ot plants, and if it is very fine ash it is able

to break down quickly and get mixed into the soil. Another benefit might be the fact that volcanic slopes

are often rather inaccesssible, especially if they are steep. Thus they can provide refuges for rare plants

and animals from the ravages of humans and livestock.

safety precautions during volcanic eruptions

Explosive volcanoes blast hot solid and molten rock fragments and gases into the air. As a result, ashflows can occur on all sides of a volcano and ash can fall hundreds of miles downwind. Dangerous mudflows and floods can occur in valleys leading away from volcanoes. If you live near a known volcano, active or dormant, be prepared to follow volcano safety instructions from your local emergency officials.

MudflowsMudflows are powerful “rivers” of mud that can move 20 to 40 mph. Hot ash or lava from a volcanic eruption can rapidly melt snow and ice at the summit of a volcano. The melt water quickly mixes with falling ash, with soil cover on lower slopes, and with debris in its path. This turbulent mixture is dangerous in stream channels and can travel more than 50 miles away from a volcano. Intense rainfall can also erode fresh volcanic deposits to form large mudflows. If you see the water level of a stream begin to rise, quickly move to high ground. If a mudflow is approaching or passes a bridge, stay away from the bridge.

Stay out of the area defined as a restricted zone by government officials. Effects of a volcanic eruption can be experienced many miles from a volcano. Mudflows and flash flooding, wildland fires, and even deadly hot ashflow can reach you even if you cannot see the volcano during an eruption. Avoid river valleys and low lying areas. Trying to watch an erupting volcano up close is a deadly idea.

EvacuationAlthough it may seem safe to stay at home and wait out a volcanic eruption, if you are in a hazardous zone, doing so could be very dangerous. Stay safe. Follow authorities’ instructions and put your volcano evacuation plan into action.

How to Prepare for a Volcano Emergency

Learn about your community warning systems and emergency plans. Be prepared for the hazards that can accompany volcanoes:

� Mudflows and flash floods

� Landslides and rockfalls

� Earthquakes

� Ashfall and acid rain

� Tsunamis

Make evacuation plans. If you live in a known volcanic hazard area, plan a route out and have a backup route in mind.

Develop an emergency communication plan. In case family members are separated from one another during a volcanic eruption (a real possibility during the day when adults are at work and children are at school), have a plan for getting back together. Ask an out-of-state relative or friend to serve as the “family contact,” because after a disaster, it’s often easier to call long distance. Make sure everyone knows the name, address, and phone number of the contact person.

Have disaster supplies on hand:

Flashlight and extra batteries First aid kit and manual Emergency food and water Non-electric can opener Essential medicines Dust masks and goggles for every member of the household Sturdy shoes

What to Do During a Volcanic Eruption

Follow the evacuation order issued by authorities. Avoid areas downwind and river valleys downstream of the volcano. Listen to a battery-operated radio or television for the latest emergency information.

If caught indoors:If caught indoors:

Close all windows, doors, and dampers. Put all machinery inside a garage or barn. Bring animals and livestock into closed shelters.

If trapped outdoors:

Seek shelter indoors. If caught in a rockfall, roll into a ball to protect your head. If caught near a stream, be aware of mudflows. Move up slope, especially if you hear the roar of

a mudflow.Protect yourself during ashfall:

Wear long-sleeved shirts and long pants. Use goggles to protect your eyes. Use a dust mask or hold a damp cloth over your face to help breathing. Keep car or truck engines off.

If possible, stay away from volcanic ashfall areas.When outside:

Cover your mouth and nose. Volcanic ash can irritate your respiratory system. Wear goggles to protect your eyes. Keep skin covered to avoid irritation from contact with ash. Clear roofs of ashfall. Ashfall is very heavy and can cause buildings to collapse. Exercise great

caution when working on a roof. Avoid driving in heavy ashfall. Driving will stir up more ash that can clog engines and stall

vehicles. If you have a respiratory ailment, avoid contact with any amount of ash. Stay indoors until local

health officials advise it is safe to go outside. Remember to help your neighbors who may require special assistance — infants, elderly people,

and people with disabilities.Let Your Family Know You're SafeIf your community has experienced a disaster, register on the American Red Cross Safe and Well web site to let your family and friends know you are safe. You may also call 1-866-GET-INFO to register yourself and your family.

A volcanic eruption can be an awesome and destructive event. Here are some tips on how to avoid danger and what to do if you're caught near an eruption.

Safety Tips

• Stay away from active volcanoes.

• If you live near an active volcano, keep goggles and a mask in an emergency kit, along with a flashlight and a working, battery-operated radio.

• Know your evacuation route. Keep gas in your car.

If a Volcano Erupts in Your Area

• Evacuate only as recommended by authorities to stay clear of lava, mud flows, and flying rocks and debris.

• Avoid river areas and low-lying regions.

• Before you leave the house, change into long-sleeved shirts and long pants and use goggles or eyeglasses, not contacts. Wear an emergency mask or hold a damp cloth over your face.

• If you are not evacuating, close windows and doors and block chimneys and other vents, to prevent ash from coming into the house.

• Be aware that ash may put excess weight on your roof and need to be swept away. Wear protection during cleanups.

• Ash can damage engines and metal parts, so avoid driving. If you must drive, stay below 35 miles (56 kilometers) an hour.

Before a Volcano

Put goggles and disposable breathing masks for each family member in yourdisaster supply kit. Stay away from active volcano sites. If you live near a known volcano, active or dormant, learn about your community warning

systems and emergency plans, and be ready to evacuate at a moment's notice. Have an emergency disaster plan for you and your family. Be prepared for the hazards that can accompany volcanoes: mudflows and flash floods landslides and rockfalls earthquakes ashfall and acid rain tsunamis

During a Volcano

Listen to a battery-operated radio or television for the latest emergency information. Follow the evacuation order issued by authorities. Avoid areas downwind and river valleys downstream of the volcano. If caught indoors: Close all windows, doors, and dampers. Put all machinery inside a garage or barn. Bring animals and livestock into closed shelters. If trapped outdoors: Seek shelter indoors. If caught in a rockfall, roll into a ball to protect your head. If caught near a stream, be aware of mudflows. Move up slope, especially if you hear the roar of

a mudflow. Protect yourself during ashfall: Wear long-sleeved shirts and long pants. Use goggles to protect your eyes. Use a dust mask or hold a damp cloth over your face to help breathing. Keep car or truck engines off. Remember: Stay out of the area defined as a restricted zone by government officials. Effects of

a volcanic eruption can be experienced many miles from a volcano. Mudflows and flash flooding, wildland fires, and even deadly hot ashflow can reach you even if you cannot see the volcano during an eruption. Avoid river valleys and low lying areas. Trying to watch an erupting volcano up close is a deadly idea.After a Volcanic Eruption

If possible, stay away from volcanic ashfall areas. When outside: Cover your mouth and nose. Volcanic ash can irritate your respiratory system. Wear goggles to protect your eyes. Keep skin covered to avoid irritation from contact with ash. Clear roofs of ashfall. Ashfall is very heavy and can cause buildings to collapse. Exercise great

caution when working on a roof. Avoid driving in heavy ashfall. Driving will stir up more ash that can clog engines and stall

vehicles.

If you have a respiratory ailment, avoid contact with any amount of ash. Stay indoors until local health officials advise it is safe to go outside.

Remember to help your neighbors who may require special assistance — infants, elderly people, and people with disabilities.

You can do many things to protect yourself and your family from the dangers a volcanic eruption can

cause. The best way to do protect yourself and your family is to follow the advice of local officials.

Local authorities will provide you with information on how to prepare for a volcanic eruption, and if

necessary, on how to evacuate (leave the area) or take shelter where you are.

If a lahar, pyroclastic flow, or lava flow is headed toward you

Leave the area immediately. If you are warned to evacuate because an eruption is imminent,

evacuate.

If you can drive rather than walk, use your vehicle to evacuate. When driving keep doors and

windows closed, drive across the path of danger if you can or away from the danger if you can

not, and watch for unusual hazards in the road.

If you are indoors

Close all windows, doors, and fireplace or woodstove dampers.

Turn off all fans and heating and air conditioning systems.

Bring pets and livestock into closed shelters.

If you are outdoors

Seek shelter indoors.

If caught in a rockfall, roll into a ball to protect your head.

If near a stream or river, be aware of rising water and possible mudflows in low-lying areas.

Move up-slope as quickly as possible.

Seek care for burns right away. Immediate care can be life saving.

If your eyes, nose, and throat become irritated from volcanic gases and fumes, move away from

the area immediately. Your symptoms should go away when you are no longer in contact with

the gases or fumes. If the symptoms continue, consult your doctor.

Protecting yourself during ashfall

Stay inside, if possible, with windows and doors closed.

Wear long-sleeved shirts and long pants.

Use goggles to protect your eyes.If ash is continually falling, you may not be able to shelter

indoors for more than a few hours, because the weight of the ash could collapse the roof of your

building and block air intakes into the building. Listen to authorities for advice on leaving the area

when ashfall lasts more than a few hours.

Exposure to ash can harm your health, particularly the respiratory (breathing) tract. To protect

yourself while you are outdoors or while you are cleaning up ash that has gotten indoors, a

disposable particulate respirator (also known as an “air purifying respirator”) may be considered.

An N-95 respirator is the most common type of disposable particulate respirator and can be

purchased at businesses such as hardware stores. It is important to follow directions for proper

use of this respirator. For more information, see NIOSH-Approved Disposable Particulate

Respirators (Filtering Facepieces) . If you don’t have a particulate respirator, you can protect

yourself by using a nuisance dust mask as a last resort, but you should stay outdoors for only

short periods while dust is falling. Nuisance dust masks can provide comfort and relief from

exposure to relatively non-hazardous contaminants such as pollen, but they do not offer as

much protection as a particulate respirator. Cleanup or emergency workers may need a different

type of breathing protection based on their work activity. Note that disposable particulate

respirators do not filter toxic gases and vapors.

Keep your car or truck engine switched off. Avoid driving in heavy ashfall. Driving will stir up ash

that can clog engines and stall vehicles. If you do have to drive, keep the car windows up and do

not operate the air conditioning system. Operating the air conditioning system will bring in

outside air and ash.

Safety Precautions for Volcanic Eruption CoverageProvided by AKE Ltd

Working guidelines

Hazards:

High speed lava flow containing toxic gases and 400 degrees + molten rock, which would be too fast for a person to out run.

Volcanic eruption clouds, liable to disperse ash over a large area (1000 km +) and affecting the local infrastructure in various ways such as:

Aircraft accessibility, diversions and delays Food supplies, crops and live stock Dangerous driving conditions: poor visibility Vehicle air filtration systems blocked causing over heating and mechanical

failure Drainage systems blocked and potential for local flooding Railway lines affected Water supplies affected

Health problems as a result of ash particles within the atmosphere such as:

Increased risk of Asthma reaction General respiratory and breathing problems Potential for severe reaction with moisture within lungs causing a cementing

affect within the lungs Local eye irritation

Preventative measures and recommendations:

Monitor weather conditions particularly wind direction (wind changes direction with attitude)

Have plans to evacuate up wind to a safe area under cover

Have clear medical evacuation plans, which may be affected by aircraft and vehicle accessibility

Where protective face masks and goggles

Make regular updates with the volcanic monitoring centre

Have sufficient water, food and medical equipment supplies, when travelling and at base location (minimum 72hours)

Once major eruption as been declared have plans in place to return to a safe location and at a suitable distance

How to Prepare for a Volcanic Eruption

Protecting your family in the event of a volcanic eruption can mean the difference between life and death. More likely, it will help you protect your health and property from volcanic "ash", rocks that can spread for many miles.[1] However, knowing how to prepare for a volcanic eruption can be confusing without the right information. Organizing a plan of attack is key to proper preparation, and educating everyone in your family or household will help to better ensure their safety and well being when disaster erupts.

Method 1 of 4: Preparation for those living in a volcano area

1

Put together an emergency supply kit. This kit is something that anyone living in a volcano zone should have prepared at all times. The kit should include such items as a first aid kit, food and water supplies, a mask to protect against ash such as one used when mowing lawns, a manual can opener, a flashlight with extra batteries or preferably a crank model, any necessary medications, sturdy shoes, goggles or other eye protection, and a battery-powered radio. Ensure that everyone in your family knows where the emergency supplies that you prepared are located.

A flashlight, phone charger, and radio combined as one, that runs on both solar power and hand cranking is the ideal

item to have ready in your house for any natural disaster event. Pack this if you have one.

2Buy proper respiratory protection. Purchase an air purifying respirator, also referred to as an N-95 disposable respirator. This can be bought at your local hardware store.

3Have the necessary communication devices ready. Use your radio or television at home to listen for volcano updates or evacuation notices.

4Be aware of what your local disaster sirens sound like. When a volcanic eruption occurs, you'll need to listen for those to go off.

5Set an emergency evacuation plan with your family. Review it in depth with them, so that each person knows what to do in the event of an eruption, how to find one another if you're apart, and how to contact neighbors and/or emergency services if you cannot get away from the property using your own transportation.

If anyone has disabilities, these need to be taken account of in the plan.

Include pets and livestock in the plan.

Discuss with your family what you will do if there are warnings to evacuate and any of you don't

want to leave. Bear in mind that it is not fair to other family members if some of you choose to

stay behind in spite of evacuation warnings, and precautions should always be taken to ensure

that those family members who want to leave can do so.

Know how to switch off all utilities and ensure that every family member old enough to be

responsible for turning off utilities knows how to do so.

Talking to children about the possibility of a disaster and what to do in the event is better than

pretending it may never happen. If children are aware that everything is planned should

something go wrong, their fear and anxiety will be reduced in the event of a disaster because

they'll know how to respond.

6Create an emergency kit specifically for your car. It should include maps, tools, a first aid kit if you haven't already packed one with your other emergency supplies, a fire extinguisher, flares, additional non-perishable food, booster cables, sleeping bagsand/or emergency blankets, and a flashlight.

Method 2 of 4: At the time of an actual evacuation

1Listen for advice and instructions. Check your pre-prepared emergency gear and have it ready to go.

2Prepare the car or other vehicle. Check that you have a full tank of gas and keep all vehicles under cover until ready to leave (ash can prevent the engines from working).

Make transportation arrangements with other families or friends if you do not have a

vehicle of your own.

3

Attend to livestock and pets. In the event that your house and property are directly impacted by the volcano, your animals will not be able to escape. Do what you can within reason to ensure their safety.

Place your livestock in an enclosed area or make arrangements to transport them as far offsite

as possible.

Make transportation plans for your family pets. Be aware that most emergency shelters will be

unable to accommodate them. If keeping your pets with you, you'll need to be sure that you

have planned ahead for enough food and water for them. Alternatively, leave messages on

social networking sites such as Twitter asking for people who are available in the area who can

board your pets temporarily until the disaster is over. You are bound to get a lot of kind offers.

4

Evacuate as instructed.

Take your prepared kit with you, and make sure that your car emergency kit is in the car.

Turn off the electric, gas, heating oil, and water in your home if time allows. It is recommended

that you don't turn off the gas unless you suspect a leak or you're instructed to do so, as it can

be weeks before a professional can get to you to turn it back on after a disaster event.[4]

Disconnect the appliances in your home if time allows.

Take the designated evacuation routes, and prepare yourself for delays. Other routes may be

blocked, so you want to ensure that you are taking the route suggested by authorities.

5

Stay put if you are instructed by the authorities to do so.

Run extra water in the sinks, bathtubs, and other containers as an emergency supply for

cleaning (use as little as possible) or purifying and drinking. You can also get emergency

drinking water from a water heater.

Don't use the toilet if there is no running water. It will make the house smell terrible. Instead,

construct if necessary and use an emergency makeshift toilet as described in the article Prepare

for a Hurricane.[5]

Close and secure all of the windows and any doors that lead to the outside.

Make sure that your heater, air conditioner and all fans are turned off.

Make sure that your fireplace damper is closed.

Continue to listen to the TV or radio for announcements and news.

Place your family into a room on ground level that does not have windows in it.

Method 3 of 4: Preparing for ash fall

The most likely hazard during a volcanic eruption is ash fall. Knowing how to deal with it is important whether you're remaining in place or you're traveling.

1

Stay indoors. Close all windows and doors; some may need to be sealed with tape or similar (damp towels work well). Stopper up any vents to outside if possible. Avoid using anything that sucks in air from outside or changes circulation patterns by heating or exhausting air, such as air conditioning or dryers.

Bring all pets indoors. If you have livestock, bring them into sheds, barns, or other shelters.

Even the garage will do as a temporary shelter. Ensure that livestock have enough food and

water.

Fill your bath and other containers with water.[7] This may become a very important water source

if ash impacts local water supplies.

Protect sensitive electronics until the ash fall has well and truly ceased; only uncover them when

the environment is totally ash-free.

2Keep your car, trucks, and any machinery under cover. If you cannot park your vehicles somewhere inside, cover them with a car cover or tarpaulin. Avoid driving unless you have no choice.

Protect all machinery from volcanic ash by covering in tarpaulins.

3If you can, disconnect drainpipes from rain gutters (eaves troughs) from downspouts or

drainpipes. Doing this can help to prevent your drains clogging. Disconnect the rainwater

supply channel to any rainwater tanks to protect your stored water and cover up any gaps on

the tank.

4Wear protective gear if you need to move around outside. If you have them, wear safety goggles to protect your eyes, and a respirator to protect your lungs, and cover the rest of your body, including your head and hands, as much as possible. Improvise a shemagh (Arab wraparound headscarf) to keep grit off your head and out of your eyes and lungs.[11] Even swimming goggles and clothing can be used to protect your eyes and breathing if that's all you have.[12]

When entering a building after being outside under ash, remove your outer layer of clothing. The

ash is difficult to remove from anything it falls on.[13]

Remove contact lenses if going outside and wear glasses instead. If the ash gets in behind

contact lenses, it can cut into your eye, causing corneal abrasions.

5After the ash fall, stay indoors and follow the radio instructions. When you do go outside, keep away from ash falls and build-up of ash and continue to wear protective clothing.

Don't drive through ash fall. It will clog your car's engine severely and cause serious abrasion

damage to the car.[15]

Keep children, pets, and animals indoors. If pets and animals have ash on their fur, hoofs, or

paws, wash it away to prevent them from ingesting it and give them plenty of water to drink.

6Try to remove ash fall from your roof. It looks like snow, but it's heavy like sand and abrasive to breathe. If the amount of ash fall is too heavy, your roof is in danger of collapsing: four inches (100mm) can collapse weaker roofs.[16]. No need to get it all off; leaving a thin layer is fine and sweeping it off would make a lot of dust. Moisten ash using a sprinkler or spray hose to dampen it before cleaning. Make sure you're wearing a protective mask and clothing.

Don't fall off your roof! It will be difficult for rescuers to notice or reach you after a volcano.

Unless you have special equipment, don't even try it on a sloped roof more than one story up, or

over hard or dangerous surfaces.

7Check for property damage. Make notes and take photographs so that you can make

your insurance claim.

Method 4 of 4: Preparing for lava flows

If your home or property is in the path of a lava flow, pyroclastic flow, surge, or lahar, it is important to be ready to evacuate immediately when local authorities ask you to.

1Follow the evacuation procedure outlined above.

2Continue listening to the radio advice when you reach a destination of safety.

3Return home only when you are informed by authorities that it is safe to do so.

Tips

If you must go outside during the ash fall, try to put something over your mouth and wear a gas mask.

Check on friends and neighbors. This is especially important if you know they may need assistance, or have special

needs.

Ideally have a landline telephone in the room in which you will be holding up. This can be used to let your emergency

contact know to keep their phone line available in case you need to let them know about any life-threatening

problems or issues.

Only use the phone lines for emergency calls to avoid clogging the communications systems.

Report broken utility lines to authorities if you see any.

Warnings

Avoid sightseeing! Not only do you endanger your own life but natural disaster sightseers are

becoming a frequent problem for emergency services workers and can hamper rescue work. At

all times stay out of designated restricted zones.

Volcanic ash is a respiratory health hazard. It impacts all people but especially those with such

respiratory problems as asthma and bronchitis.