EARTHQUAKES!!!

EarthquakesEarthquakes

• Earthquake: Sudden movement of rock sliding along a fault in the earth’s crust

• Releases energy as this occurs.

• Energy release produces strong vibrations called seismic waves.

Energy ReleaseEnergy Release• Edges of the plates get stuck while

the rest of the plate keeps moving.—Energy stored up

• When the force of the moving blocks finally overcomes the friction of the jagged edges of the fault and it unsticks, all that stored up energy is released.

• The energy radiates outward from the fault in all directions in the form of seismic waves like ripples on a pond. –This is the earthquake

Earthquake WavesEarthquake Waves

• Focus- point of earthquake origin

• Epicenter- point on earth’s surface above the focus

• Primary Waves ( P-wave)– Travel through solids and

liquids– Travel FAST!

• Secondary Waves (S-waves)

– Only travel through solids– Travel SLOWER than P-waves

Longitudinal Waves (L-waves)-- Travel on earth’s surface

http://losangeles.cbslocal.com 3/17 la eq

http://earthguide.ucsd.edu/mystery_detectives/teach/epicenter/ia_graph_travel_time_animation.html

Mystery Earthquake animations: http://earthguide.ucsd.edu/mystery_detectives/teach/epicenter/show.html

TO know the TO know the EPICENTER:(where quake started)

• Seismic waves radiate out from the source in all directions.

• Siesmograph stations recieve p and s waves and use the difference in arrival time to determine the distance away.

• Different stations compare the information recorded at the same time.

Seismic Station picks up p and s waves and determines they came from

an earthquake 10 km away.

But 10 km from which direction?

A second seismic station records the same quake at 5 km away.This narrows down the epicenter to 2 spots.

To pinpoint the epicenter, 3 seismic stations must record

the quake. (triangulation)

VOLCANOESVOLCANOES

• A hole in Earth’s crust through which lava flows from underground.

Origin of MagmaOrigin of Magma

• Molten rises from the Earth’s asthenosphere (upper mantle) to the Earth’s surface through cracks creating a volcano.

Most volcanoes occur along plate Most volcanoes occur along plate boundariesboundaries

Hot SpotsHot Spots

• Volcanically active sites that arise in places where large quantities of magma move to the surface in large, column-like plumes– Can occur away from plate boundary

– When under a oceanic plate, volcanic island chains forms

• Mountains—folding and faulting; convergent continental boundaries

• Plateau– eroded mountain