Bell Ringer Monday 11/30/09 Where do most volcanoes tend to form? a. convergent plate boundaries b. divergent plate boundaries c. hot spots d. all of the above

EARTHQUAKES

Earthquakes – vibrations of the Earth’s crust

Elastic Rebound Theory – theory that rocks that are strained past a certain point will fracture and spring back to their original shape

Seismic Waves – energy released as vibrations when rocks fracture; these vibrations travel through the Earth

Aftershocks – a tremor that follows and is smaller than a major earthquake

Focus – the area along a fault where slippage first occurs (see Figure 2-p 739- copy it into your notes) Epicenter – the point on Earth’s surface directly above the focus

Earthquakes that cause the most damage usually have a shallow focus (a depth in the Earth of less than 70 km) Earthquakes with a deep focus cause less damage because much of their energy has been used up before the seismic wave reaches the surface

3 Major Earthquake Zones Pacific Ring of Fire Mid-ocean ridges Eurasian-Melanesian belt

Fault Zone – group of interconnected faults (example – San Andreas Fault in CA)

Seismograph – instrument used to detect seismic waves 3 types of waves P waves – primary waves Fastest waves Move through solid and liquid material S waves – secondary waves Move through solid material only

L waves – long waves Slowest waves Also called surface waves Occur when P waves and S waves reach the surface Destructive to Earth’s surface

Locating the epicenter of an Earthquake Use a time-distance graph to plot arrival times of P waves, S waves and L waves Need three locations to determine the epicenter of earthquake

Richter scale – used to express the magnitude of an earthquake Magnitude – is a measure of the energy released by an earthquake

Largest recorded earthquake measured 9.6 on the Richter scale Microquakes – have magnitudes of less than 2.5 on the Richter scale

Earthquake Dangers Building collapse Landslides Fires Falling objects Flying glass Explosions from broken gas and electric lines Flooding from broken dams

To withstand an earthquake, buildings should: Have strong walls Be built on soil or rock that is firm

Tsunami – a giant ocean wave caused by an earthquake with an epicenter on the ocean floor An earthquake may also trigger underwater landslides – which may 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 your home.

During an earthquake, stay calm Get under a desk or table or stand in a doorway Stay away from windows and heavy furniture If in a car, stop in a place away from tall buildings, tunnels, power lines, and bridges; stay in the car until the tremors stop

After an earthquake, be cautious Check for fire and fire hazards Wear shoes when walking in broken glass Avoid downed powerlines and objects touched by downed wires

Earthquake warnings & predictions Strange animal behavior Seismic gaps – a place where the fault 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 Shelby County!! Write a brief newspaper article detailing the events that occurred before, during, and after an earthquake. Be as creative as you can be. However, your article must include a picture and the scientific words that we have been studying in class.