volcano dictionary

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Volcano Dictionary

A

'a'a'A'a (pronounced "ah-ah") is a

Hawaiian term for a lava flow that

has a rough, broken-up, spiny

surface. It is composed of broken

lava blocks called clinkers. The

interior of 'a'a is very dense.

accretionAccretion is the

accumulation of sediment

(mud, sand, etc.) by

deposition, often occurring

along a shoreline or in a

river delta.

acid rainAcid rain is

polluted and

harmful to the

environment.

active volcanoAn active volcano is one that

has erupted in recorded

history or is currently

erupting.

aerosolAn aerosol consists of tiny

particles of liquids or

solids suspended in the

air.

aftershockAftershocks are small

earthquakes that occur

after a large earthquake.

airfallAirfall (also called

ashfall) is volcanic

ash that falls from an

ash cloud or a

volcanic column.

andesiteAndesite is a type of volcanic

rock. This gray to black rock is

composed of about 54 to 62

percent silica (SiO2), plus some

iron and magnesium.

ash cloudAn ash cloud (also called

an eruption cloud) is the

cloud of ash that forms

after some volcanic

eruptions.
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ashfa

llAshfall

(also

called

airhfall)

is

volcanic ash

that

falls

from an

ashclou

d or a

volcani

c

column.

ash,

volcani

c

Volcanicash is a

harsh

abrasive

type of

ash

(unlike

ash from

a wood

fire) that

is made

up of

small

rock,

mineral,

and

volcanic

glass

fragment

s (these

fragment

s are lessthan 0.1

inch (2

mm) in

diameter)

.

asthenosphereThe asthenosphere (also spelled aesthenosphere) is a part of

the Earth's upper mantle that exhibits plastic properties. It is

located below the lithosphere (the crust and upper mantle),

between about 100 and 250 kilometers deep.

atmosphericshock wave

An atmospheric shock

wave is compressed air

that is formed by a

volcanic eruption.

atomEverything is made up of

tiny atoms. An atom is

the smallest part of an

avalancheAn avalanche is a a large mass offalling and/or sliding material.

Avalanches can be composed of

rock, snow, soil, or ice. Volcanic

eruptions can cause avalanches.
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element that has the

properties of that

element.

B

background extinctionsBackground extinctions are those

extinctions that occur continually

throughout time. These extinctions

are caused by small changes in

climate or habitat, depleted

resources, competition, and other

changes that require adaptation and

flexibility. Most extinctions (perhapsup to 95 per cent of all extinctions)

occur as background extinctions.

ballistic

fragmentA ballistic

fragment is a

piece of rock

that is ejected

from a volcano

with great

speed.

basaltBasalt is a type of volcanic

(igneous) rock. This hard,

dark rock is composed of 45

to 54 percent silica (SiO2)

and is often rich in iron and

magnesium. Basalt is the

most common type of rock

in the Earth's crust - most ofthe sea floor is made up of

basalt.

basaltic lavaBasaltic lava is a lava composed

ofmolten basalt. This type of

lava erupts at temperaturesfrom 1100 to 1250 C. Basalt

lava has a low viscosity

(resistance to flow); it flows

relatively quickly. Shield

volcanoes are almost entirely

composed of basalt.

base surgeA base surge is a

cloud of rock debris,

water, and steamthat moves close to

the ground at high

speeds. It is formed

by an explosive

volcanic eruption.

batholithA batholith is a huge body of

igneous rock that solidified

under that Earth but nowhas at least 100 square

kilometers (40 square miles)

exposed. Half Dome at

Yosemite National Park,

California, USA, is a granite

batholith.

bathypelagicBathypelagic means of,

pertaining to, or living in

the deep ocean near the

bottom.

1,000,000,000

billionA billion is a thousand

million. Multicellular life

evolved on Earth about a

billion years ago.

biomassBiomass is the amount of

animal and plant life in an

area. Biomass is usually

expressed in units of weight

per volume.


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biotaBiota is the

animal andplant life of

an area.

blockA volcanic block is a chunk of rock (over 64

mm) that is ejected (thrown) from a volcano.Blocks usually originate from the volcano's

cone and are solid chunks of older lava flows.

A block is one size oftephra.

blowdownA blowdown is a area

of trees that has beenblown over by a

volcanic blast.

bombA volcanic bomb is a chunk of viscous lava (over 64 mm) that is

ejected (thrown) from a volcano. Since they are still viscouswhen ejected, they often have rounded, aerodynamic shapes.

Types of bombs include: breadcrust bombs, ribbon bombs,

spindle bombs, spheroidal bombs, and "cow-dung" bombs.

1,000,000,0

00

bya"bya" stands for

billions of years

ago.

C

calderaA caldera is a large depression

formed from a collapsed volcano.

Calderas are often circular or

elliptical. Crater Lake (in Oregon,

USA) is an example of a largecaldera (it is 16 miles across).

Caldera comes from the Spanish

word for Cauldron.

Cenozoic eraThe "Age of Mammals" (65

million years ago - today), saw

the emergence of familiar life

forms, humans, the modernlook of the continents, and a

cooling climate. The Cenozoic

followed the Mesozoic Era.

cindersCinders are small

fragments of lava

that are about

1/2 inch (1

centimeter)across.
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cinder coneA cinder cone is a cone-shaped

volcano. Its steep sides are formed

by volcanic loose, fragmented

cinders that fall to the Earth close to

the vent. The lava flows through a

single vent that is usually only up to

about 1,000 feet tall. There is

usually a bowl-shaped crater at the

top. As the gas-filled lava erupts into

the air, the lava fragments and

forms cinders.

composite

volcanoA composite volcano

is a volcano that has asteep volcanic cone

that is built up by

dense lava flows and

pyroclastic debris.

Also called a

stratovolcano.

condensationCondensation is the

process in which a

vapor (a gas) is cooled

to the liquid phase.

Clouds are formed by

the condensation of

atmospheric water

vapor.

conduitA volcanic conduit is a passage through which magma (molten rock) flows in a

volcano.

Top of Form

Forward Backward

Bottom of Form

continental driftContinental drift is the movement of the Earth's continents. The land masses are
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hunks of Earth's crust that float on the molten core. The ideas of continental drift

and the existence of a supercontinent (Pangaea) were presented by Alfred Wegener

in 1915.

continental platesThe crust of the Earth is broken into plates. Theplates are enormous chunks of rock that float atop

the soft mantle. The plates are moving at a speed

that has been estimated at 1 to 10 cm per year.

Continental plates are thicker, older, and less dense

than oceanic plates. These plates are about 125

kilometers thick and are made of granite that is

about 3 billion years old.

continental shelfThe continental shelf is the

part of the ocean floor next to

each of the continents. The sea

floor slopes gradually from the

continent to a depth of about

650 feet (200 m). Beyond the

continental shelf the sea floor

drops steeply.

coreThe core is the innermost

layer of the Earth. It consists

of iron-nickel; it is under great

pressure and is very hot. The

inner core is solid ; the outer

core is molten.

Coriolis forceThe Coriolis force is the force that

results from the rotation of the Earth

around its axis; it makes storms rotate

counterclockwise in the Northern and

clockwise in the Southern

Hemispheres. The French

engineer/mathematician Gustave-

Gaspard Coriolis discovered this force

craterA crater is a

circular

depression in

the ground. It

has steep

sides and

contains a

volcanicvent.
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in 1835. This force has effects on

water currents, but has no effect on

the direction of water going down a

drain.

Cretaceous periodFlowering plants appeared and dinosaurs were at their

height during the Cretaceous period, 146-65 million years

ago. There was a mass extinction (the K-T mass

extinction) at the end of the Cretaceous, marking the end

of the dinosaurs and many other species. Modern-day

sharks existed during the Cretaceous period.

crust

The Earth's crust is itsoutermost, rocky layer.

crystallizationCrystallization is the

process in which

magma solidifies into

solid, crystalline rock.

currentA current is a non-periodic horizontal movement of water.

Currents are caused by winds, temperature differentials,

and other forces. They are NOT caused by tidal forces (the

gravitational forces of the Moon and Sun). Some majorcurrents include the Gulf Stream in the Atlantic Ocean and

the Humboldt Current in the Pacific Ocean.

D

daciteDacite is a type of

volcanic rock that is

light-colored and rich in

silica (63 to 68 percent).

debris avalancheA debris avalanche is a

sudden rock/soil/debris slide

and flows with great speed

from a volcano.

debris flowA debris flow (also called a

mudflow or lahar) is a

moving mixture of rock,

water, and other debris.
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decibelDecibels (abbreviated dB) are the unit of

measuring the loudness (or intensity) of sounds. 0

dB is the faintest audible sound. The decibel scale

is logarithmic. Blue whale calls are up to 188 dB;

this is the loudest animal sound, and is painful to

the human ear. Volcano eruptions are one of the

loudest sounds on Earth and are over 272 dB.

degreeA degree is a

measure oftemperature

or angle.

diatremeA diatreme is a

volcanic vent orpipe that is

formed by gas-

charged magma.

dikeA dike is a sheet-like intrusion of magma (molten rock)

that froces its way through a layer of fractured rock. The

magma flows through cracks in the rock and later cools

and solidifies into a sheet of igneous rock.

domeA lava dome is a dome-shaped mound that is

formed around a vent by

viscous lava.

dormant volcano

A dormant volcano is a volcano that isnot active now, but may erupt in the

future.

dustVolcanic dust is a solidified lava that is tiny

particles. It is ejected from volcanos duringan eruption.

E
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EarthThe Earth is the third planet from the

sun.

ejectaEjecta is material that has been thrown

from a volcanic erutption. Some ejecta are

lava bombs and tephra (pyroclastic

material).

elementAn element is a

chemically pure

substance

composed of

atoms of a singletype.

Eocene epochThe Eocene epoch (58-37

million years ago) was the

time when primitive whales

and many other mammals

evolved.

Eon Time

Phanerozoi

c Eon

540 million years

ago through today

Proterozoic

Eon

2.5 billion years ago

to 540 million years

ago

Archaeozoi

c Eon

3.9 to 2.5 billion

years ago

Hadean Eon4.6 to 3.9 billion

years ago

eonTwo or more geological eras form

an eon, which is the largestdivision of geological time,

lasting hundreds of millions of

years.
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epicenterThe epicenter is the point

on the Earth's surface

directly above the place

that an earthquake

occured.

epipelagicEpipelagic menas of or

about the upper part of the

ocean in which there is

enough light to support

plants.

epochAn epoch is a division of a

geologic period; it is the

smallest division of

geologic time, lasting

several million years.

equator

The equator is animaginary circle

around the earth (or

other planet or

moon), halfway

between the north

and south poles.

eraTwo or more

geological periods

comprise an era,

which is hundredsof millions of years

in duration.

eruptionAn eruption is

volcanic activity

in which lava,

tephra, or gases

are released.

eruption cloudAn eruption cloud (also

called an ash cloud) is

the cloud of ash, gas

and rock fragmentsthat forms after some

volcanic eruptions.

eruptive ventAn eruptive vent is a

vent from which

volcanic material is

released.

evaporationEvaporation is the process

in which a liquid is

transformed into a

gaseous form.

extinctAn animal species that is extinct

has died out. Most animal species

that ever existed have gone

extinct, including all the

dinosaurs.

extinct volcanoAn extinct volcano is a

volcano that is not likely to

erupt again.

extrusive igneous rockExtrusive rocks are igneous rocks that have cooled

at the surface of the Earth. They usually have a fine-

grained texture.
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F

fissureA fissure is a

crack in a rocks.

A volcanic

fissure is one

from which lava

erupts.

fold mountainsFold mountains are a type of mountain range that is formed when

two continental plates collide (or one continental plate colliding

with an oceanic plate). The colliding crust is compressed and

pushed upwards (uplifted), forming mountains. For example, the

Himalayas were slowly formed when the Indian plate collided with

the Asia-European plate millions of years ago.

fumarole

A fumarole is a vent from which volcanic gases (like sulphur vapor) escape.Fumaroles can occur along small cracks or long fissures.

G

GASGas is a phase of matter

in which the molecules

are widely separated,

move around freely, and

move at high speeds.

GEOLOGICAL TIMEThe history of the earth is described

in geological time, which is measured

in millions of years and billions of

years. The divisions used are: eon,

era, period, and epoch.

GEOLOGYGeology is the

study of the
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Earth's structure,

including rocks.

GEOLOGIS

TA geologist is

a scientist

who studies

geology.

glacier outburst

floodA glacier outburst flood

is a sudden flood caused

as water flows quickly

from a glacier or a

glacier-dammed lake. It

is caused as volcanic

activity under the

glacier melts the ice.

GONDWANALANDGondwanaland (also known as Gondwana)

was the southern supercontinent formed

after Pangaea broke up during the Jurassic

period. It included what are now South

America, Africa, India, Australia, andAntarctica.

GREENHOUSE EFFECTThe greenhouse effect is an increase in the temperature of a planet

as heat energy from sunlight is trapped in the atmosphere. Excess

carbon dioxide and water vapor increase this effect. The greenhouse

effect is strong on Earth and Venus, maintaining warm temperatures.

grabenA graben (or

rift) is a

valley

between two

faults.

graniteGranite is a type of igneous rock

GUTENBERG, BENOBeno Gutenberg ( June 4, 1889 - 1960) was a
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(volcanic rock that has cooled) that

is light-colored and coarse grained.

Granite is characterized by the

minerals orthoclase and quartz with

some plagioclase feldspar and iron-

magnesium minerals. Granite

underlies much of the continents.

German geophysicist. In 1913, he accurately

determined the size of the core of the Earth.

Gutenberg discovered that the Earth has a

low-velocity zone in the upper mantle; this

zone is now called the Gutenberg

discontinuity. Gutenberg published a series ofpapers with Charles Richter (they were titled

"On Seismic Waves" and published between

1931 and 1939) and Seismicity of the Earth

(published in 1941).

GUTENBERG DISCONTINUITYThe Gutenberg discontinuity separates the

outer core and the mantle of the Earth.

GUYOTA guyot is a flat-topped, undersea

mountain (a seamount) formed from

a volcano.

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half-lifeThe half-life of a radioisotope is the amount of time it takes

for half of the radioisotope to decay.hemisphereA hemisphere is half

of a sphere.

HoloceneThe Holocene (meaning

"entirely recent" in Greek) is

the most recent epoch in

geologic time, lasting from

about 11,000 years ago until

the present day (the time

since the last Ice Age).

hotspotA hot spot is a an area

in the Earth's

lithosphere through

which magma (molten

rock) rises. Volcanoes

often erupt over hot

spots.

hydrologic cycleThe Hydrologic cycle (also

known as the water cycle) is

the journey water takes as it

circulates from the Earth to

the sky and back again.

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cano/glossary/indexv.shtmlhttp://www.enchantedlearning.com/subjects/volcano/glossary/indexw.shtmlhttp://www.enchantedlearning.com/subjects/volcano/glossary/indexx.shtmlhttp://www.enchantedlearning.com/subjects/volcano/glossary/indexy.shtmlhttp://www.enchantedlearning.com/subjects/volcano/glossary/indexz.shtml


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ice ageAn ice age is a

time lasting

thousands of

years during

which the Earth

is very cold and

largely covered

by ice andglaciers.

igneous intrusion

An igneous intrusion (also calleda laccolith or a plutonic

formation) is a formation in which

magma (molten rock) is trapped

beneath the surface of the Earth

and pushes the rock located

above it into a dome shape. It

has a flat base and a convex

upper surface. The magma cools

and solidifies, and eventually, it is

exposed (as the fractured

sedimentary rock above it erodesaway).

igneous rock

When molten rock cools,igneous rock is formed.

Intrusive rocks are igneous

rocks that have formed (and

cooled slowly) beneath the

surface of the Earth. Extrusive

rocks are igneous rocks that

have formed (and cooled more

quickly) at the surface of the

Earth (like obsidian). Some

igneous rocks include granite,

obsidian (volcanic glass),basalt, and andesite porphyry.

ignimbriteIgnimbrite (meaning "fire rain

stone") is a type of igneous rock

that is formed in the pyroclasticflow (the pumice flow deposit) of

violently explosing volcanoes.

Ignimbrite forms as molten lava

and ash fuse; this rock is

streaked with parallel bands of

black glass. The texture of

ignimbrite varies from hard to

soft.

impact

craterImpact craters

are the remains

of collisions

between an

asteroid or

meteorite and

the Earth.

index fossil

Index fossils are commonlyfound fossils that are limited in

time span. They help in dating

other fossils. For example:

trilobites were common during

the Paleozoic, but not found

before the Permian period, and

ammonites were common

during the Mesozoic Era, but

not found after the Cretaceous

period.

intrusive igneous rockIntrusive rocks are igneous rocks that

have formed (and cooled slowly)

ionAn ion is an atom

that is missing one or
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intertidal

zone

The intertidal

zone is wherethe sea meets

the land.

beneath the surface of the Earth. These

rocks usually have a coarse-grained or

medium-grained texture, like granite.

more electrons; ions

have an electrical

charge.

Iridium anomalyIridium is an element that is rare on the

Earth's surface, but abundant on chondritic

meteors. The presence of excess Iridium at

the K-T layer (the Iridium anomaly) supports

the Alvarez asteroid theory.

ISOTOPEAn isotope of an element is another

form of the same element, that has

a different number of neutrons in

the nucleus (giving it a different

atomic weight).

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J

JURASSIC PERIODBirds evolved and many dinosaurs flourished during the Jurassic period, 208-146

million years ago.
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L

laccolithA laccolith (also called a plutonic

formation or an igneous intrusion) is a

formation in which magma (molten

rock) is trapped beneath the surface of

the Earth and pushes the rock located

above it into a dome shape. It has a

flat base and a convex upper surface.

The magma cools and solidifies, and

eventually, it is exposed (as thefractured sedimentary rock above it

erodes away). Laccolith means "cistern

stone" in Greek.

laharA lahar (also called a

mudflow or debris flow)

is a moving mixture of

rock, water, and other

debris that falls down

the slopes of a volcano

and/or a river valley.

Lahar is an Indonesianword

lapilliLapilli are pieces of

rock or lava that

range from 2 and

64 millimeters

across. Lipilli are

thrown into the air

by volcanic

explosions

lateral blastA lateral blast is a

volcanic eruption

that occurs on the

side of a volcano;

the energy of the

blast is directed

horizontally.

latitudeLatitude is the angular

distance north or south

from the equator to a

particular location. The

equator has a latitude of

zero degrees. The north

and south poles have a

LaurasiaLaurasia was the northern

supercontinent formed after Pangaea

broke up during the Jurassic period.

Laurasia included what are now

North America, Europe, Asia,
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latitude of 90 degrees.

The rest of the world is

between zero and ninety

degrees.

Greenland, and Iceland.

lavaLava is molten

rock. It usually

comes out oferupting

volcanoes.

lava bombA volcanic bomb is a chunk of viscous lava (over

64 mm) that is ejected (thrown) from a volcano.

Since they are still viscous when sjected, they

often have rounded, aerodynamic shapes. Type

of bombs include: breadcrust bombs, ribbon

bombs, spindle bombs, spheroidal bombs, and"cow-dung" bombs.

lava domeA lava dome is

a dome-shaped

mound that is

formed around

a vent byviscous lava.

lava flowA lava flow is moving

mass of molten lava onthe Earth's surface. The

solidified lava deposit

from a molten lava flow

is also called a lava flow.

lava lakeA lava lake is a

lake of basaltic

lava contained

in a volcanic

caldera.

lava tubeA lava tube is a tube-like, underground

conduit formed by flowing lava. The

flowing lava crusts over at the edges and

drains out onto lower ground - what is left

is a smooth, tube-like tunnel with

hanging lava stalactites and a flat floor -

a lava tube.

liquid

Liquid is a phase ofmatter in which

the molecules are

close together and

can move around

slowly.

lithosphere

lithospheric plates

Llithospheric plates are aseries of slabs that make up

the Earth's hard outer shell.

There are 16 major

lithospheric plates that float on

softer layers of the Earth's

mantle.
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The lithosphere is the solid,

rocky, outer part of the Earth

consisting of the crust and the

upper mantle.

Littoral Zone

The littoral

(intertidal)

zone is where

the sea meets

the land.

loessLoess is a

deposit of

tiny,

windblownparticles.

longitudeLongitude is the angular distance east or west of

the prime meridian (the north-south line that

passes through Greenwich, England) to a particular

location. Greenwich, England has a latitude of zero

degrees. The farther east or west of Greenwichyou are, the greater your longitude. Midway

Islands (in the Pacific Ocean) have a longitude of

180 degrees (they are on the opposite side of the

globe from Greenwich).

Volcano Info


Volcano

Volcano Activities


M

maarA maar is a shallow, flat-

bottomed crater that forms

above a diatreme (volcanic

vent) when steam explodes.

Maars range in size from 200

maficMafic refers to dark-

colored igneous rock or

magma that have

significant amounts of

iron and magnesium. For

magmaMagma is molten rock
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to 6,500 feet in diameter and

from 30 to 650 feet deep.

Maars often fill with water and

form lakes.

example, olivine, augite,

and hypersthene are

mafic rocks.

(lava) from which

igneous rock forms.

Magma is be formed

from many types of

rocks, including basalt,

andesite, dacite, andrhyolite

magmachamberA magma chamber

is an underground

cavity filled with

gas-rich magma

(molten rock). This

magma erupts

through volcanoes.

magnetic fieldThe Earth's magnetic

field is aligned with the

north and south poles,

and has reversed many

times during geologic

history. Sharks may use

the magnetic field of

the Earth for navigation

purposes on migrations.

magnitudeThe intensity of an earthquake is

described by a number in the Richter

scale, called the magnitude. The

magnitude of an earthquake iscalculated from the logarithm of the

amplitude of waves recorded by

seismographs. A magnitude 2.0 or less

earthquake is called a

microearthquake and is not felt by

people. A magnitude 4.5 or more

earthquake can be measured by

seismographs all over the world.

Tsunamis can be caused by undersea

earthquakes of magnitude 7.5 or

greater.

mantleThe mantle is the layer

of the Earth located

between the crust and

the molten core.

mass

extinctionMass extinction

is the process

in which huge

numbers ofspecies die out

suddenly. The

dinosaurs (and

many other

species) went

extinct during

Mesozoic EraThe Mesozoic Era ("The

Age of Reptiles"),

occurred from 245-65

million years ago. It is

divided into the Triassic,

Jurassic, and Cretaceous

periods. Dinosaurs,

mammals, and flowering

plants evolved during the

Mesozoic, and Pangaea

metamorp

hic rockMetamorphic

rocks are

compacted by

pressure and

heat from deep

inside the
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the K-T

extinction,

which was

probably

caused by an

asteroidcolliding with

the Earth.

broke up. The era ended

with the K-T mass

extinction.

earth.

meteorA meteor is a meteoroid that has

entered the Earth's atmosphere,

usually making a fiery trail as it falls.

It is sometimes called a shooting star.

Most burn up before hitting the Earth.

meteorite

A meteorite is a meteorthat has fallen to Earth.

Meteorites are either

stone, iron, or stony-

iron.

meteoroid

Meteoroids are tinystones or pieces of

metal that travel

through space.

1,000,000

millionA million is a

thousand

thousand. The

dinosaurs lived

millions of

years ago.

mineralA mineral is a

naturally-occurring

solid of definite

chemical

composition whose

atoms usually form

a regular pattern.

Miocene epochThe Miocene epoch was a geologic time span

that lasted from 24 million to 5 million years

ago. During the Miocene, modern birds andmany mammals evolved (including the

horses, dogs, bears, South American

monkeys, and apes in southern Europe).

Ramapithecus appeared; this primate was

pehaps an ancestor of man. The climate was

relatively warm (as compared to the earlier

Oligocene or the later Pliocene). There were

extensive grasslands (and grasses

diversified), and the interior of the continents

were relatively dry; northern coniferousforests expanded. Kelp forests appeared in

the seas. In North America, the Sierra Nevada

Mountains and the Cascade Mountains were

formed; in the South America, the Andes

Mountains arose. The Bering land bridge

formed during the Miocene, connecting

Russia and Alaska, allowing many animals to
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migrat across continents. The Isthmus of

Panama also formed during this time.

Australia became very dry (but went through

wet and dry periods). In Europe, the

Mediterranean Sea and Indian Ocean were

separated (they had been connected by theTethys Sea).

Mohorovicic, AndrijaAndrija Mohorovicic (1857 - 1936)

was a Yugoslavian geophysicist.

After examining seismic wavesfrom the 1909 Kulpa Valley

earthquake, Mohorovicic

theorized that a boundary

between the Earth's crust and the

upper mantle existed (about 50

km beneath the surface) in which

the speed of earthquake waves

became very rapid. This region is

now called the Mohorovicic

discontinuity. A crater on the dark

side of the moon was also named

for Mohorovicic.

MOHOROVICIC

DISCONTINUITYThe Mohorovicic

discontinuity separates

the crust and the upper

mantle of the Earth.

monogeneticvolcano

A monogenetic

volcano is one that

was formed during a

relatively short time

period and during a

single eruption. Most

monogenetic

volcanos are basaltic.

mudflowA mudflow (also called a debris flow or lahar) is a moving

mixture of rock, water, and other debris.

1,000,000

mya"mya" stands for

millions of years ago.


Volcano
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Volcano Info

Volcano Activities

and Printouts

Types of Volcanoes The Ring of Fire

N

neckA neck (also called a

volcanic plug) is

solidified lava that fills

the conduit of a volcano.

nereticPertaining to the

shallow waters near the

shore over the

continental shelf.

nuees ardenteNuees ardente (also called

pyroclastic flow) is very hot gas

and ash that explodes from a

volcano at high speeds.

Volcano Info


Volcano

Volcano Activitiesand Printouts

Types of Volcanoes The Ring of Fire

oceanAn ocean is a vast body of salt water. Oceans cover

more than three-quarters of the surface of the

obsidianObsidian (also called Apache

tears) is a volcanic glass that is

usually black, but is
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Earth. The oceans on Earth include the Pacific

Ocean, the Atlantic Ocean, the Indian Ocean, and

the Arctic Ocean. The ocean floors are composed

mostly ofbasalt.

occasionally red, brown, gray,

green (rare), dark with

"snowflakes," or even clear.

This glassy, lustrous mineral is

found in lava flows, and

obsidian stones can bemassive. Obsidian is formed

when viscous lava (from

volcanos) cools rapidly. Most

obsidian is 70 percent silica.

Obsidian has a hardness of 5

and a specific gravity of 2.35.

The pin above is mahogany

(brown) obsidian.

oceanic platesThe crust of the Earth is broken into plates. Theplates are enormous chunks of rock that float

atop the soft mantle. The plates are moving at a

speed that has been estimated at 1 to 10 cm per

year. Oceanic plates (those that are under the

ocean) are thinner, younger, and denser than

continental plates. These underwater plates are

about 75 kilometers thick and are made of

basalt rock. They are relatively young since

plate formation (seafloor spreading) occurs at

the margins of oceanic plates.

oceanographyOceanography is

the science that

studies the

physical geography

of oceans.

outcropAn outcrop is

a place where

bedrock is

visible on the

surface of the

Earth.
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outgassingOutgassing is the

release of gases

into the

atmosphere during

volcanic eruptions.

A lot of of our

atmosphere

(including water

vapor, nitrogen,

and argon) came

from outgassing.

ozoneOzone is a form of

oxygen (O3); it consists

of three connected

oxygen atoms. Ozone is

formed when oxygen

molecules (O2) bonds

are broken by high

energy (bombardment

by energetic electrons

or high energyradiation).

ozone layerThe ozone layer is a region of the

stratosphere which contains most

(about 90%) of the Earth's

atmospheric ozone. It is about10-25

miles (15-40 km) above the Earth's

surface. The ozone layer shields the

Earth from Ultraviolet B rays that

come from the Sun. The ozone layer is

becoming depleted, and there is an

"ozone hole" over Antarctica.

Volcano Info


Volcano

Volcano Activities


P

PahoehoePahoehoe (pronounced

"pah-hoy-hoy") is a

Hawaiian term for lava

that, when solid, has apaleontology
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smooth or rope-like

surface.

Paleontology is the branch

of biology that studies the

forms of life that existed in

former geologic periods,

chiefly by studying fossils.

paleontologistA paleontologist is a scientist

who studies paleontology, the

forms of life that existed in

former geologic periods,

chiefly by studying fossils.

Paleozoic eraThe Paleozoic era

(540 to 245 million

years ago) saw an

explosion of new lifeforms. It ended with

the largest mass

extinction in history

and was followed by

the Mesozoic Era.

PangaeaPangaea was a supercontinent

consisting of all of Earth's land

masses. It existed during the Permian

andJurassic period. It began breaking

up during the Jurassic period, forming

continents Gondwanaland and

Laurasia, separated by the Tethys

Sea.

Pele's hairPele's hair is a

Hawaiian term for

natural spun glass

that can be as much

as 2 m long. It isformed from the

fountaining of fluid

basaltic lava,

cascading lava falls,

or from turbulent lava

flows.

periodThe period is

the basic unit

of geological

time in which

a single type

of rock system

is formed,

lasting tens of

millions ofyears.

Permian periodAlso known as "The Age of

Amphibians" (280 to 245

million years ago), this is

the time when Pangaea

formed and Earth's

atmosphere was

oxygenated to modern

levels. It ended with thelargest mass extinction

and was followed by the

Mesozoic Era. Ancient

sharks swam the seas

during the Permian period.

phases of matterMatter can exist in four phases (solid,

liquid, gas, and plasma) and a few other

extreme phases, like critical fluids and

degenerate gases. The phase diagram

of water (above) shows its phase at
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various temperatures and pressures.

pillow lavaPillow lava is lava that

cools under the sea, with

an interconnected, sack-

like form.

pipeA pipe is a vertical passageway that runs through the

Earth's crust under a volcano. Pipes are formed as

magma (molten rock) travels upward through the

crust. Pipes are often filled with breccia and other rock

debris.

platesThe crust of the Earth is broken intoplates. The plates are enormous chunks of

rock that float atop the soft mantle. The

plates are moving at a speed that has

been estimated at 1 to 10 cm per year.

Oceanic plates (those that are under the

ocean) are thinner and denser than

continental plates.

Top of Form

Forward Backward

plate tectonicsPlate tectonics is the now-established

theory that chunks of the Earth's crust

(plates) float on the surface and change

both position and size over time.

Bottom of Form

plutonic formationA plutonic formation (also called a laccolith or an igneous

intrusion) is a formation in which magma (molten rock) is

plugA plug (also called

a volcanic neck) is

solidified lava that
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trapped beneath the surface of the Earth and pushes the rock

located above it into a dome shape. It has a flat base and a

convex upper surface. The magma cools and solidifies, and

eventually, it is exposed (as the fractured sedimentary rock

above it erodes away).

fills the conduit of

a volcano.

PrecambrianThe Precambrian is the time 540 before

the Cambrian period (before million years

ago). It is the time from when the Earth

formed until simple life-forms evolved.

precipitationPrecipitation is rain, sleet, hail, snow, or

other condensation products falling

from the atmosphere. Precipitation onEarth is is key in the water cycle.

prehistoricPrehistoric refers to the time

before people began

recording history in writing.

This time varies from cultureto culture.

pumicePumice is a light-weight, spongy rock that is formed

in explosive volcanic eruptions. This igneous rock is

light and porous, containing a network of gas bubbles

in volcanic glass and minerals. Pumice can form from

any types of magma, including basalt, andesite,dacite, and rhyolite.

pyroclasticPyroclastic (meaning "fire

fragmented") refers to broken-

up rocks, pumice, ash, and

other bits of material that are

formed in a volcanic eruption.

pyroclastic flowA pyroclastic flow is an avalanche of pyroclastic

materials (broken rocks, pumice, and ash) and

hot gases that erupts from within a volcano. A

pyroclastic flow travels at up to 100 miles per

hour. Within the flow, temperatures can reach

500 degrees C.
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Q

Quaternary period

The Quaternary period, "The Age of Man" (1.8 million yearsago to the present), is the most recent period ofgeological

time.

quartzQuartz is a common

crystalline mineral.

Volcano Info


Volcano

Volcano Activities


R

radioisotope datingRadioisotope dating is used to find

out how old fossils are. Different

radioisotopes are used for

different geologic time periods

because of their different half-

repose

Repose is thetime between

volcanic

eruptions.

reticulite

Reticulite (also called thread-lace scoria) is a very light form

of pumice. It is formed during

very high fountaining volcanic

eruptions, when a lot of air is

included in the rock
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lives.

rhyoliteRhyolite is a a type

of volcanic lava or

rock that is usually

light in color; it

contains 69

percent silica and

is high in

potassium and

sodium.

rhyolite caldera complexthese are the most explosive

volcanoes. They do not look like

common volcanoes -- after an

eruption, the result is a caldera

(crater) caused when the area

around the vent collapses.

Examples are Yellowstone in

Wyoming, USA and Lake Taupo in

New Zealand (which erupted

around A.D. 80).

Richter, Charles F.Charles Francis Richter

(April 26, 1900- April 30,

1985) was a who developed

the Richter scale, a

logarithmic scale that

measures the intensity of

an earthquake. He

developed it in 1935 at the

California Institute of

Technology.

Richter scaleThe Richter scale is a logarithmic scale

that measures the intensity of an

earthquake. It was developed in 1935 by

Charles F. Richter. The magnitude of an

earthquake is calculated from the

logarithm of the amplitude of waves

recorded by seismographs. Beno

Gutenberg also contributed to the more

general application of the Richter scale.

A magnitude 2.0 or less earthquake is

called a microearthquake and is not felt

by people. A magnitude 4.5 or more

earthquake can be measured by

seismographs all over the world.

riftA rift (or

graben) is

a valley

between

two

faults.

ring of fireThe ring of fire is an area

around the Pacific Ocean that

is high in volcanic, mountain-

building, and seismic activity.

rockA rock is an aggregation of

solid matter, a random

conglomerate ofminerals. The

rock cycleThe rock cycle decribes

the relationship between

igneous, sedimentary,

runoffRunoff is water (or

other liquids) that

drains or flows from the
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earth's crust is made of rock.

There are three types of rock:

igneous, sedimentary, and

metamorphic. Petrology is the

scientific study of rocks.

and metamorphic rocks.

James Hutton (1727-

1797) first developed the

concept of the rock cycle.

land into streams and

rivers, and eventually

into the seas. The water

is generally from rain or

snowpack melt.

S

sciencePeople study

science to

learn about the

physical world.

scoriaScoria are bomb-sized (greater

than 64 mm across) pyroclastic

fragments that are formed as

blobs of lava cool when they are

blasted through the air. Scoria

are filled with cavities formed by

trapped air bubbles.seafloor spreadingSeafloor spreading is the

movement of two oceanic plates

away from each other, which

results in the formation of new

oceanic crust and a mid-ocean

ridge.

seamountA seamount is an underwater

mountain that rises at least 1000

meters above the sea floor. Some

seamounts rise above the water's

surface. Most seamounts arevolcanic in orgin; only a few are

non-volcanic (caused by uplifting).

sedimentary

rockSedimentary rock is

rock that has formed

from sediment. Most

fossils are found

sedimentary rock.

seismographA seismograph is a

device that records and

measures seismic waves

(vibrations in the Earth),

like those fromearthquakes.
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shield volcanoA shield volcano is a volcano

that has gently sloping sides.Shield volcanoes are

composed mostly ofbasalt

(whose lava flows easily and

quickly). The biggest

volcanoes on Earth (like those

on the islands of Hawaii) are

shield volcanoes.

shocked quartzShocked quartz is quartz

that has undergone

deformation due to extreme

pressure and heat. It has

been found in the layer thatmarks the K-T boundary,

leading credence to the

Alvarez impact theory.

skylightA skylight is a an

opening in the roof of alava tube. Skylights

are formed either

when part of the roof

collapses or as a gap in

the tube when the

tube initally forms.

side ventA side vent is an opening in

the side of a volcano

through which volcanic

materials (like lava, gases,

and pyroclastic debris)

erupt.

silicaSilica is a very common

mineral composed of

silicon and oxygen (SiO2).

Silicates make up about

95% of the Earth's crust.

silicatesSilicates are minerals

composed of silicon and

oxygen with one or more

other elements. Silicates

make up about 95% of the

Earth's crust.

skyThe sky on Earth appears blue because

our atmosphere scatters the blue

colors from the sunlight (which consists

of all colors of light). The sky on

planets with a different atmospheric

composition would appear to be a

different color.

solidA solid is one phase

of matter, a phase in

which the molecules

are very close

together and cannot

move around.

spreading ridgeA spreading ridge is

an area of the ocean

floor in which new

crust is being formed

as magma erupts.
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states of matterMatter can exist in four states or phases

(solid, liquid, gas, and plasma) and a few

other extreme phases (like critical fluids and

degenerate gases). The phase diagram ofwater (above) shows its phase at various

temperatures and pressures.

stishoviteStishovite is a very

dense form of quartz

that has only been

found in meteorite

impact craters, inwhich quartz has

undergone high-

pressure shock.

stratovolca

noA stratovolcano

is a composite

volcano.

subductionA subduction is a phenomenon in which one part of the

Earth's crust (a plate) is pushed underneath another

plate as two plates collide. The descending crust meltsas it is pushed deep into the Earth's mantle. Subduction

destroys crust and recycles it back into the mantle.

subduction zoneA subduction zone is an

area on a planet's crust in

which the edge of an

oceanic continental plate

is being pushed beneathanother plate.
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sublimeSubliming is when a

material goes directly

from being a solid to

being a gas (it skips

the liquid phase

altogether).

supervolcanoA supervolcano is an enormous volcano that is an order of

magnitude larger than ordinary volcanoes. A supervolcano

occurs when a huge magma chamber in the Earth's crust

erupts after being under great pressure, causing a large

caldera to form as the land over the magma chamber

collasps

volcano dictionary

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