# 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.

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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 card 2.I.N. 3.Pencil/Pen 4.Summary

Earthquakes

Earthquakes Earthquake- a movement of Earth’s lithosphere (rigid solid) that occurs when rocks in the lithosphere suddenly shift, releasing stored energy! 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. 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)- Stress (in earthquake terms)- a force that squeezes rocks together, stretches or pulls them apart, or pushes them in different directions. a force that squeezes rocks together, stretches or pulls them apart, or pushes them in different directions. Does stress occur at… Does stress occur at… Convergent plate boundaries? Convergent plate boundaries? Divergent plate boundaries? Divergent plate boundaries? Transform boundaries? Transform boundaries? Stress = Folds and Faults!

Folds=Plastic Deformation A bend in layers of rock in response to stress A bend in layers of rock in response to stress Form where rocks are squeezed together, but do not break Form where rocks are squeezed together, but do not break This doesn’t lead to earthquakes This doesn’t lead to earthquakes

Faults Faults- Faults- A fracture, or break, in Earth’s lithosphere A fracture, or break, in Earth’s lithosphere Blocks of rocks move (scrape) past each other Blocks of rocks move (scrape) past each other San Andreas Fault San Andreas Fault

Where do earthquakes occur?? Most earthquakes happen along plate boundaries Most earthquakes happen along plate boundaries Ring of Fire- belt around the Pacific plate Ring of Fire- belt around the Pacific plate Over 75% of all earthquakes occur here Over 75% of all earthquakes occur here http://www.cleanvide osearch.com/media/ac tion/yt/watch?v=gRlj5 vjp3Ko

Why Exactly do Earthquakes Happen? Elastic Rebound- The sudden return of elastically deformed rock to its original shape 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. Elastic rebound occurs when more stress is applied to rock than the rock can withstand. During elastic rebound, energy is released as an earthquake During elastic rebound, energy is released as an earthquake

How do we measure earthquakes? 2 different scales Seismic waves vs destruction! Seismic waves vs destruction!

Measuring Earthquakes Modified Mercalli scale- Rates earthquakes based on observations of the intensity of ground shaking and damage 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 Richter scale- Rates earthquakes based on measurements of the times and amplitudes of the seismic waves Created by Charles Richter in the 1930’s 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 To measure earthquakes and pinpoint their epicenters, geologists record seismic waves using seismographs Seismograph- Seismograph- a device that can detect and record seismic waves a device that can detect and record seismic waves Creates a seismogram Creates a seismogram

What is a Seismogram? Seismogram- Seismogram- A tracing of earthquake motion created by a seismograph A tracing of earthquake motion created by a seismograph

Seismic Waves – the reason earthquakes are Dangerous! Seismic waves- Seismic waves- the energy released during an earthquake carried by vibrations the energy released during an earthquake carried by vibrations 3 main types: 3 main types: P waves P waves S waves S waves Surface waves Surface waves

Seismic Waves P waves (primary waves)- longitudinal waves similar to sound waves P waves (primary waves)- longitudinal waves similar to sound waves Move through solid and liquid material Move through solid and liquid material Compress and expand the ground Compress and expand the ground Similar to an accordion or a slinky Similar to an accordion or a slinky

Seismic Waves S waves (secondary waves)- Transverse waves, like light. S waves (secondary waves)- Transverse waves, like light. They cannot travel through liquids They cannot travel through liquids

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

Seismic Waves Surface Waves- develop when seismic waves reach Earth’s surface Surface Waves- develop when seismic waves reach Earth’s surface Move more slowly than P and S waves Move more slowly than P and S waves Produce larger movements Produce larger movements Create greater damage Create greater damage

Where do Earthquakes Happen? Earthquakes- occur because stress forces have exceeded the strength of rock. Earthquakes- occur because stress forces have exceeded the strength of rock. Focus- the location beneath Earth’s surface where an earthquake begins. Focus- the location beneath Earth’s surface where an earthquake begins. Epicenter- the location on Earth’s surface directly above the focus. Epicenter- the location on Earth’s surface directly above the focus.

The S-P time method… How it’s used: How it’s used: Collect several seismograms from different seismographs (at different locations) Collect several seismograms from different seismographs (at different locations) Plot seismograms on a distance-time graph Plot seismograms on a distance-time graph Draw circles around the locations based on the 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 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