At the end of this lesson you should be able to:

• define earthquakes and identify causes

• identify how earthquakes are predicted and measured and how they are located

• discuss how waves affect a variety of mediums

• identify the effects of volcanoes

• discuss how we can use models to predict earthquakes or volcanic eruptions

On the white board below, type what you believe causes Earthquakes and/or volcanoes.

Geologic events, such as earthquakes and volcanic eruptions, can be deadly.

The basis for all geologic events is plate tectonics: the movements of Earth’s lithospheric plates.

Earth's lithospheric plates are in constant motion. Therefore, earthquakes and volcanic eruptions are possible any time.

Many of these events are potentially dangerous. Destruction wrought by earthquakes and volcanic eruptions can cost

billions of dollars and kill thousands of people.

Earthquake.usgs.gov

Locations of VolcanoesThe popular conception of a volcano is a high mountain with a hole at the top where the volcano erupts. In fact, a volcano is

any location where molten rock and other materials make their way to Earth’s crust and onto the surface. Usually, but not

always, volcanoes build mountains, as the once-molten rock hardens on Earth’s surface.

Volcanoes are found worldwide, often where two tectonic plates meet. Many of the world’s volcanoes are along the Ring of Fire

surrounding the Pacific Ocean. The map below shows the locations of Earth’s tectonic plates and the location of

volcanoes.

Effects of VolcanoesMagma is molten rock that forms under Earth’s surface. Lava is

molten rock that reaches the surface.

There are different kinds of volcanic eruptions

Some volcanoes erupt more or less continuously. These

eruptions comprise “thinner” lava that oozes out of the volcano, without a violent

eruption, they have a type of “quiet” eruption. The lava flows onto the ground and

hardens.

Effects of Volcanoes

Eruptions can be violent, spewing forth hot chunks of rock, gases, dust and lava. Violent eruptions

result when “thick” lava and magma plug the volcano,

allowing trapped gases to build up. When the volcano can no

longer contain the trapped gases, a violent eruption shoots clouds

of dust, gas, and smoke high into the atmosphere. Some eruptions

can blow off the top of a mountain, leaving a large crater.

The mixture of rock, lava, and ash that spews from a violent eruption is called pyroclastic

material. (Pyro-means “fire,” and –clastic mean “pieces.”)

Types of VolcanoesThe various types and locations of eruptions lead to different

classifications for volcanoes.

Composite Volcanoes – are generally steep-sided slopes

with violent eruptions. Pyroclastic material and lava

build layers within the volcano, making a tall cone.

Mount Etna in Italy (Sicily) is a composite volcano. Other examples include Mount St. Helens in Washington and

Mount Fuji in Japan.

Cinder Cone Volcano – Cinder is another term used to

describe the ash and dust ejected from a volcano.

Layers of cinder and lava form mounds of material.

Cinder cone volcanoes are usually located near other types of volcanoes. This

cinder cone is located on the side of Mount Etna.

Shield volcanoes generally have gently sloping sides. They form because “quiet” lava eruptions build layers over time. The Hawaiian

islands are formed by shield volcanoes

The Mauna Loa volcano in Hawaii is a shield volcano. The volcano rises from the

seafloor, making it the largest volcano on Earth.

Lets test what you have learned so far:

1. The basis for all geologic events is:

A. Aliens B. Plate TectonicsC. Earth’s rotation

Lets test what you have learned so far:

1. Many of the world’s volcanoes are along:

A. The equator B. Sahara DesertC. The Ring of Fire

Lets test what you have learned so far:

1. These types of volcanoes generally have steep-sided slopes with violent eruptions:

A. Cinder ConeB. CompositeC. Shield

Earthquakes occur anywhere rock structures are under stress from movement. The upper portion of Earth’s crust is brittle.

Tectonic plate motion can cause the crust to break, resulting in an earthquake.

Earthquakes occur most often at transform plate boundaries. The best-known transform plate boundary runs through

California.

Here, the eastern side of the Pacific Plate meets the western side of the North America Plate. The two plates slide past each

other, building stress within the rock structures. The stress causes the rocks to bend. The rocks deform as more stress

builds

The deformation transfers energy from the movement of tectonic plates to rock structures. Therefore, deformed rocks along fault lines contain a high amount of potential energy. At

some point the rocks can no longer bear the stress and suddenly give way. All the stored energy is released, and an

earthquake occurs.

Scientists model the buildup and release of energy in rocks as elastic rebound. In this process, Earth’s rocks are equated to a rubber band. If you pull back a rubber band, it gains potential energy. If you pull far enough, the rubber band snaps, with a sudden release of that energy. In other words, the excessive

deformation of the rubber band results in elastic rebound, which we experience as the release of potential energy suddenly transformed to kinetic energy. A similar process takes place

when the potential energy of stressed rock is transformed to the kinetic energy of moving rock, an earthquake.

The sudden release of energy where rock ruptures causes seismic waves to move outward in all directions. A seismic wave

is any ground movement that results from energy released during an earthquake. The point in the Earth’s crust where the rock ruptures is the focus. The point on Earth’s surface directly

above the focus is the epicenter.

Earthquake WavesEarthquakes cause intense shaking of the ground. The shaking

is caused by waves moving through the ground. Scientists study the seismic waves using a seismograph (also called a

seismometer). These machines record ground movement by making lines on paper. The recorded lines on paper are called a

seismogram.Both a seismograph and a seismogram are shown in the images below:

There are two main types of waves, as follows:

I. 1st type: Body waves A. P waves

1. Also know as primary waves or compression waves 2. Travel through the solid and liquid parts of Earth 3. Fastest earthquake waves a. Travel about 5 km per second b. Always the 1st waves to appear on seismogram 4. Cause ground to move horizontally back and forth through compression

There are two main types of waves, as follows:

I. 1st type: Body waves B. S waves

1. Also know as secondary waves or shear waves 2. Can travel through Earth’s solid portions only 3. When they hit the liquid core, S-waves are no longer able be detected a. P-waves bounce off the liquid core. S-waves are absorbed at the core 4. Cause ground to move back and forth in an S-shaped pattern.

There are two main types of waves, as follows:

II. 2nd type: Surface waves A. Rayleigh waves

1. Also known as R-waves 2. Cause intense damage to the surface, especially to buildings 3. Have a rolling motion, like the waves of the ocean

There are two main types of waves, as follows:

II. 2nd type: Surface waves B. Love waves

1. Also know a L-waves 2. Cause intense damage to the surface, especially to buildings 3. Have a side-to-side motion similar to the movement of a snake.

Lets test what you have learned so far:

1. Examples include S-waves and P-waves:

A. Body wavesB. Surface wavesC. Ocean waves

Lets test what you have learned so far:

1. The point inside Earth where rock ruptures:

A. EpicenterB. Elastic ReboundC. Focus

Lets test what you have learned so far:

1. A machine used to record ground motion:

A. SeismographB. EpicenterC. Seismogram

Predicting earthquakes

Stress in rock structures can be measured. Earthquakes are usually sudden, but some rock structures can give clues. For example, there is obvious stress on rocks in the following image. At some point, the rocks will be unable to withstand the stress and will suddenly rupture, causing an earthquake.

Dangers of earthquakes and volcanoes

• Dangers associated with earthquakes and volcanoes can

include landslides and tsunamis.• A tsunami is a high-speed, long-wavelength wave that

happens when large volumes of ocean water are displaced by earthquakes, volcanoes, or underwater landslides. The waves are often mistakenly called “killer waves.” The common depiction of a tsunami as a giant, curved wall of water is also incorrect.

Dangers of earthquakes and volcanoes

List one impact that you think earthquakes or volcanoes

have on us or the environment:

Lab

Lab: Seismograph 2

Once you click on the seismograph station of your choice, this diagram will appear.

Lab: Measuring P to S Waves

To start, you will need to highlight where the P-wave begins and continue highlighting to the start of the S-wave.

Did I correctly measure from the P-Wave to the S-Wave?

Click the red X for no or the green check for yes

Graphing the Distance

Locating the Epicenter

Locating the Epicenter

Epicenter

The area where all three circles intersect is known as the _____________.

A. P WaveB. S WaveC. Epicenter

Completing the Lab

• Once you have completed the lab you will need to

complete the questions on the lab document.• When I transfer the lab document to you, you will

want to save it and use this later to answer your questions on.