Bell Ringer
Monday 11/30/09
Where do most volcanoes tendto form?
a. convergent plate boundaries
b. divergent plate boundaries
c. hot spots
d. all of the above
EARTHQUAKES
•Earthquakes – vibrationsof the Earth’s crust
•Elastic Rebound Theory –theory that rocks that arestrained past a certain pointwill fracture and spring backto their original shape
•Seismic Waves – energyreleased as vibrations whenrocks fracture; thesevibrations travel through theEarth
•Aftershocks – a tremorthat follows and is smallerthan a major earthquake
•Focus – the area along a faultwhere slippage first occurs(see Figure 2-p 739- copy itinto your notes)
•Epicenter – the point onEarth’s surface directlyabove the focus
•Earthquakes that cause the mostdamage usually have a shallowfocus (a depth in the Earth ofless than 70 km)
•Earthquakes with a deep focuscause less damage because muchof their energy has been used upbefore the seismic wave reachesthe surface
•3 Major EarthquakeZones
•Pacific Ring of Fire
•Mid-ocean ridges
•Eurasian-Melanesianbelt
•Fault Zone – group ofinterconnected faults(example – San AndreasFault in CA)
•Seismograph – instrument used todetect seismic waves
•3 types of waves
•P waves – primary waves
•Fastest waves
•Move through solid and liquidmaterial
•S waves – secondary waves
•Move through solid material only
•L waves – long waves
•Slowest waves
•Also called surface waves
•Occur when P waves andS waves reach the surface
•Destructive to Earth’ssurface
•Locating the epicenter of anEarthquake
•Use a time-distance graph toplot arrival times of P waves,S waves and L waves
•Need three locations todetermine the epicenter ofearthquake
•Richter scale – used toexpress the magnitude of anearthquake
•Magnitude – is a measure ofthe energy released by anearthquake
•Largest recorded earthquakemeasured 9.6 on the Richterscale
•Microquakes – havemagnitudes of less than 2.5on the Richter scale
•Earthquake Dangers
•Building collapse
•Landslides
•Fires
•Falling objects
•Flying glass
•Explosions from broken gas andelectric lines
•Flooding from broken dams
•To withstand an earthquake,buildings should:
•Have strong walls
•Be built on soil or rock thatis firm
•Tsunami – a giant ocean wavecaused by an earthquake with anepicenter on the ocean floor
•An earthquake may also triggerunderwater landslides – whichmay cause a series of tsunamis
•Earthquake safety
•Before an earthquake, be prepared
•make a plan
•have emergency supplies
–Canned food & bottled water
–Flashlight, portable radio, &batteries
•Learn how to turn off the gas,water, and electricity in yourhome.
•During an earthquake, stay calm
•Get under a desk or table or standin a doorway
•Stay away from windows andheavy furniture
•If in a car, stop in a place awayfrom tall buildings, tunnels,power lines, and bridges; stay inthe car until the tremors stop
•After an earthquake, be cautious
•Check for fire and fire hazards
•Wear shoes when walking inbroken glass
•Avoid downed powerlines andobjects touched by downed wires
•Earthquake warnings & predictions
•Strange animal behavior
•Seismic gaps – a place where thefault is locked and unable to move;likely place for future earthquake
•Scientists detect:
•Slight ground tilting
•A decrease in local P waves
Giant Earthquake Hits ShelbyCounty!!
•Write a brief newspaper articledetailing the events that occurredbefore, during, and after anearthquake. Be as creative as you canbe. However, your article mustinclude a picture and the scientificwords that we have been studying inclass.