EARTHQUAKES Earthquakes Earthquake Sudden movement of rock sliding

EARTHQUAKES!!!

Earthquakes • 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 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 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/ep icenter/ia_graph_travel_time_animation. html Mystery Earthquake animations: http: //earthguide. ucsd. edu/mystery_detectives/teach/ep icenter/show. html

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)

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

Origin 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 boundaries

Hot 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