Plot the earthquakes on the map Where do Earthquakes occur?
Mar 26, 2015
Plot the earthquakes on the map
Where do Earthquakes occur?
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An earthquake is any sudden movement of the Earth’s Crust
Stress is:•A force per unit area•A force acting on rock to change the shape or volume
Graph courtesy of: http://geology.csupomona.edu/dwtarman/alert%20files/structural%20topics/stress.htm
* 3 Types:
Result of 2 opposite forces
Result of at least 2 opposite forces; may be as many as 4
forces
Result of 2 opposite forces
Plastic Deformation
Results in folded rock but not earthquakes
Elastic Deformation
Leads to Earthquakes
* A bend in rock
* Does NOT result in earthquakes
* Occurs when rock is in plastic state
* Anticline: convex (upward) fold
* Syncline: concave (downward) fold
Diagrams courtesy of:: http://www.glossary.oilfield.slb.com/Display.cfm?Term=syncline
•A SURFACE ALONG WHICH ROCKS BREAK AND SLIDE PAST EACH OTHER
* RESULTS IN AN EARTHQUAKE
Photos courtesy of: http://pubs.usgs.gov/gip/earthq1/how.html
Once that happens the rock breaks (faults), movement occurs along the fault and energy is released (earthquake).
Rocks under pressure will continue to bend and deform until their elastic limit is reached.
Photo courtesy of: http://www.thetech.org/exhibits/online/quakes/faults/cycles1.html
Pressure Changes
Excessive Sediment Layers-crack plates
Plates undergo vertical movement above bumps in the mantle
Most earthquakes occur at plate boundaries.
Transform boundaries experience the most quakes