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
Dec 15, 2015
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
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
Measuring Earthquakes
Modified Mercalli scale- Rates earthquakes based on observations of the intensity of ground shaking and damage
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
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
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