Earthquakes and Deformation of the Crust 1. 2 Deformation of the Crust Stress –Force that causes pressure in the rocks of the earth’s crust Strain –Change.

Earthquakes and Deformation of the Crust

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Deformation of the Crust

• Stress –Force that causes pressure in the

rocks of the earth’s crust

• Strain

–Change in the shape or volume of rocks from stress


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Rock Layers Experience

shearing compression

tension


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Folding

• When rock becomes permanently deformed without breaking–Anticline–Syncline–Monocline


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Anticline• When rock layers are folded

and uplifted into arch like patterns


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Syncline• Downward folds like a

bowl

• Or sink


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Monocline• Gently dipping fold in the rock

layers


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Faulting • Fault

–Break in rock

–Rocks on either side of the break move

• Fracture–Break in rock with no movement.


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Folds Vs. Faults


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Footwall & Hanging Wall


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Normal Fault • Fault plane is 45° or more• Hanging wall drops relative to the

footwall• Divergent boundaries


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Reverse Fault

• Hanging wall moves up relative to the footwall

• Due to compression

Fault plane is 45°


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Thrust Fault

• Special kind of reverse fault

• Fault angle is less than 45°


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Strike Slip


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Reverse Normal

Thrust Blind Thrust

Strike Slip

Oblique


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Mountain Formation

• Smallest to Biggest–Mountain

–Mountain range

–Mountain system

–Mountain belt


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Mountain Belts

• Evidence that mountains are created when lithospheric plates collide

• Name some examples• Appalachians?

–Formed where plates collided in the past


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Folded Mountains

• Formed when tectonic movements have squeezed the rock layers together like an accordion


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Fault Block Mountain

• Formed when faulting breaks the Earth’s crust into large sections

• The sections are uplifted and tilted


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Fault Block Mountain and Graben


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Grabens• long narrow valley formed by

faulting and downward slippage of a crustal block


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Volcanic Mountains

• Formed when molten rock erupts onto the earth’s surface

•


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Dome mountains

• Created when molten rock pushes up rock layers on the Earth’s surface

• Then the layers then are worn away in places, leaving separate high peaks.


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Earthquake

• vibration of the Earth

• produced by the rapid release of energy


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• Elastic Rebound Theory explains the cause of earthquakes.


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Elastic Rebound Theory


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Elastic Rebound Theory• Rocks are moving slowly on

either side of a fault• if the fault is locked in place,

stress in the rocks increases• Rocks that are strained past a

certain point will fracture, move, and spring back to their original shape


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Locked

• When friction prevents the rocks on either side of a fault from sliding past each other


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• Most earthquakes occur along or near the edges of the earth’s – lithospheric plates

• Fault Zone– group of interconnected faults


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San Andreas Fault Zone• has formed where the edge of the

Pacific plate is slipping north along the North American plate


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San Andreas Fault zone


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Aftershocks

• tremor that follows a major earthquake

• is smaller

• Caused or related to the major earthquake


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Focus

• zone along a fault where slippage first occurs

• produces an earthquake

• 0rigin of the quake


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Epicenter

• point on the Earth’s directly above the focus of an earthquake

• May or may not be the point of greatest shaking, most damage


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Focus and Epicenter


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Seismograph

• instrument for recording seismic waves


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Seismograph


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Seismograph


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Modern Day Seismograph


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Richter Scale•Measure of the magnitude of a quake, or energy released

•31.7 times more energy is released for every whole number

• 3.1 to 5.1?• 31.7 x 31.7 = approx. 1000


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Seismic Waves


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P waves S waves

L waves

Speed Fastest Middle Slowest

Amp-litude

Smallest Middle Largest

Period Shortest Middle Longest

Medium

Solid, gas, liquid

Solids On the Surface


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Earth Quake Location


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Earthquakes and Deformation of the Crust 1. 2 Deformation of the Crust Stress –Force that causes pressure in the rocks of the earth’s crust Strain –Change.

Documents

wall earthquakes

stress earthquakes

cause of earthquakes

molten rock

crustal block earthquakes

crustanticlinewhen rock

rock layersearthquakes

crustfoldingwhen rock