Earthquakes

So, what’s the significance of this “special purpose” map?...

Earthquakes happen most frequently at

plate boundaries or margins

Divergent Boundarieso Quakes are frequent and mild because plates separation prevents buildup of pressureo Quakes are shallow because Oceanic crust is thin and is not being pushed into the mantle

Convergent Boundarieso More intense because colliding plates build up pressure over time and release ito Quakes are deeper because crust is being pushed into the mantle in subduction process

Transform Boundarieso Less predictableo Some plates pass each other smoothly, creating frequent but small quakeso Some plates lock up for long periods, building enormous pressure that is released in more rare but larger quakes

Earthquakes also occur along FAULT lines that are not necessarily at plate

margins.

FAULTS are simply BREAKS in the rocks that are found in the Earth’s crust (continental or

oceanic).

Photo of an eroded Strike-Slip Fault in

California

Strike-Slip Faults are also known as TRANSFORM

Faults

Earthquake Terminology

FAULT - break in the rock along which crustal movement takes

place

FOCUS - the actual spot in the crust where movement originated

EPICENTER - the place on the surface directly above the Focus;

usually the place most affected by movement

SEISMIC WAVES - movement that radiates away from the focus, both within the crust and on the surface

Seismograph

Earthquake intensity is described as MAGNITUDE

An Earthquake’s

MAGNITUDE

is rated on the

RICHTER SCALE

TSUNAMISWaves generated from Earthquakes that occur

under the ocean http://www.youtube.com/watch?feature=endscreen&NR=1&v=w3AdFjklR50

The sudden crustal movement sends

waves of water in all directions. When the

waves move from deeper water to

shallower areas near the coastline, large waves build up and

crash onto the coastline.

TSUNAMIS can travel GREAT distances in

relatively SHORT periods of time...

ANATOMY of a TSUNAMI

TSUNAMIS begin with movement in the crust over a body of water, usually in SUBDUCTION ZONES. http://www.youtube.com/watch?NR=1&feature=endscreen&v=bG37DEAb3Bc

The SEISMIC WAVES transfer movement from the crust to the water. http://www.youtube.com/watch?NR=1&feature=endscreen&v=aHljDIDf6js

At the EPICENTER, the water movement spreads out in all directions.http://www.youtube.com/watch?v=APDvwlL8jZk&feature=endscreen&NR=1