Bell Work 12/5/14

1. How do you get a spaghetti noodle to bend and not break?

2. How do you break a spaghetti noodle?

3. How can you apply this concept to the lithosphere?

On your desk:1. P.R.I.D.E

card2. I.N.3. Pencil/Pen4. Summary

Earthquakes

Earthquakes

Earthquake- a movement of Earth’s lithosphere (rigid solid) that occurs when rocks in the lithosphere suddenly shift, releasing stored energy!

They’re Caused by a Build-up of STRESS in Earth’s Crust

As tectonic plates move, they cause stress in the crust, which in turn produces folds and faults.

Stress in Earth’s Crust

Stress (in earthquake terms)- a force that squeezes rocks

together, stretches or pulls them apart, or pushes them in different directions.

Does stress occur at… Convergent plate boundaries? Divergent plate boundaries? Transform boundaries?

Stress = Folds and Faults!

Folds=Plastic Deformation

A bend in layers of rock in response to stressForm where

rocks are squeezed together, but do not break

This doesn’t lead to earthquakes

Faults

Faults-A fracture, or

break, in Earth’s lithosphere

Blocks of rocks move (scrape) past each other

San Andreas Fault

Where do earthquakes occur??

Most earthquakes happen along plate boundaries

Ring of Fire- belt around the Pacific plateOver 75% of all earthquakes occur here

http://www.cleanvideosearch.com/media/action/yt/watch?v=gRlj5vjp3Ko

Why Exactly do Earthquakes Happen?

Elastic Rebound-The sudden return of elastically deformed rock to its original shape

Elastic rebound occurs when more stress is applied to rock than the rock can withstand. During elastic rebound, energy is released as an

earthquake

How do we measure earthquakes?

2 different scalesSeismic waves vs destruction!

Measuring Earthquakes

Modified Mercalli scale- Rates earthquakes based on observations of the intensity of ground shaking and damage

San Francisco earthquake of 1906 was an 11

Modified Mercalli Scale

Measuring Earthquakes

Richter scale- Rates earthquakes based on measurements of the times and amplitudes of the seismic waves

Created by Charles Richter in the 1930’s

How exactly do we Measure earthquakes?

To measure earthquakes and pinpoint their epicenters, geologists record seismic waves using seismographs

Seismograph- a device that can detect

and record seismic waves Creates a seismogram

What is a Seismogram?Seismogram-

A tracing of earthquake motion created by a seismograph

Seismic Waves – the reason earthquakes are Dangerous!

Seismic waves- the energy

released during an earthquake carried by vibrations

3 main types: P waves S waves Surface

waves

Seismic WavesP waves (primary waves)- longitudinal

waves similar to sound wavesMove through solid and liquid materialCompress and expand the ground

Similar to an accordion or a slinky

Seismic WavesS waves (secondary waves)-

Transverse waves, like light.They cannot travel through liquids

S waves can’t pass through liquid…this is why we know the outer core is

a liquid!

Seismic WavesSurface Waves- develop when seismic waves

reach Earth’s surfaceMove more slowly than P and S wavesProduce larger movements

Create greater damage

Where do Earthquakes Happen?

Earthquakes- occur because stress forces have exceeded the strength of rock.

Focus- the location beneath Earth’s surface where an earthquake begins.

Epicenter- the location on Earth’s surface directly above the focus.

The S-P time method…

How it’s used: Collect several

seismograms from different seismographs (at different locations)

Plot seismograms on a distance-time graph

Draw circles around the locations based on the distance-time graph

At the point where 3 lines intersect is the earthquake epicenter

Locating Earthquakes

http://www.uwgb.edu/dutchs/EarthSC-102VisualsIndex.HTM

Locating Earthquakes

http://www.uwgb.edu/dutchs/EarthSC-102VisualsIndex.HTM

Locating Earthquakes

http://www.uwgb.edu/dutchs/EarthSC-102VisualsIndex.HTM

Adopt a Volcano!!

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