# Chapter 8 and 9 Review

 WHAT CAUSES AN EARTHQUAKE ?
 VIBRATIONS OF EARTH PRODUCED BY THE SUDDEN RELEASE OF ENERGY
 describe the location of an epicenter and focus
 Epicenter is the location on the surface of Earth directly above the focusFocus is the point within the Earth where the earthquake starts
 What is elastic rebound hypothesis ? How does it relate to earthquakes ?
 Elastic rebound hypothesis is the release of built up energy.Most earthquakes are produced by the release of elastic energy stored in rocks that has been subjected to great focus
 Describe aftershocks and foreshocks ?
 Aftershocks are small quakes that come after a major earthquake Foreshocks are small quakes that come before a major earthquake
 How are earthquakes measured ?
 Intensity and magnitude
 Describe surface, S waves, and P waves
 Surface waves-seismic waves that travel along Earths outer layer moves up and down,and side to side S waves-shake particles at right angles to their direction of travel,slower than P waves but faster than S waves P waves-they push(compress),and pull(expand) rocks in the direction the waves travel
 How do scientist locate earthquakes ? (distance and directions)
 The difference in velocities of P waves provides a way to locate the epicenter.Scientists use a travel time graph in which one needs at least 3 seismograph station data
 Where do most earthquakes occur ?
 Around the edge of the Pacific Ocean
 Describe each of the different scales used to measure earthquakes.Which one measure intensity and which one measures magnitude of an earthquake.
 Richter scale-measures the magnitude of an earthquake.Based on the amplitude of the largest seismic wave.Intensity-is a measure of the amount of earthquake shaking at a given location based on the damageMagnitude-is a measure of the size of seismic waves or the amount of energy released at the source of an earthquake
 What is liquefaction ?
 Stable soil turns into a liquid that is not able to support buildings or other structures
 What causes tsunamis ? What warning system is used ?
 A tsunami is called a seismic sea wave.A tsunami is triggered by an earthquake.It occurs where a slab of ocean floor is displaced vertically along a fault.Scientist use water levels in tidal qauges to determine if a tsunami is forming
 What are some other dangers that can occur due to earthquakes ?
 Landslides and ground subsidence or the sinking of the ground triggered by the vibration occurs,many houses are destroyed,and fires are caused when gas and electrical lines are cut
 Describe the three layers of crust ?
 Crust- lithosprere,consists of the crust and the uppermost mantle,it is cool and rigid shell,100 km thickMantle- asthenosphere,soft and a weak layer,below the lithosphere,rocks are close to meltingOuter core- is liquid and 2260 km thick,metallic iron and generates the Earths magnetic fieldInner core- solid layer having a radius of 1220 km thick,has high temperature and high pressure,made mostly of nickel
 Describe continental drift ?
 The continental drift hypothesis stated that the continents had once been joined together to form a single supercontinent
 Who came up with the idea of continental drift ?
 Alferd Wegner
 What is Pangaea ?
 Supercontinent
 When is Pangaea ?
 500 MY
 What kind of evidence is present to verify the idea of continental drift ?
 shorelines look like they fit together,fossils organisms found on different land masses,mountain belts end at one coastline only reappear on landmasses across the ocean,ancient climates
 What are plate tectonics ?
 According to plate tectonics theory the uppermost mantle,along with the overlying crust,behaves as a strong rigid layer
 How many plates are there ? Name each.
 There are 7 major plates and 6 minor plates.The largest is the Pacific plate which covers most of the pacific oceanNorth american south americanpacificafricaneurasianaustralin-indianantarticcarribeannazcaphillipinearabiancocosscotia
 What happens to plate boundaries ?
 The grinding movements of Earths lithosphere plates generate earthquakes,create volcanoes,and deform large masses of rock into mountains
 Describe each of the boundaries and tell what is happening at each.
 Divergent boundaries occur when two plates move apart.This process results in upwelling of material from the mantle to create a new seafloorConvergent-The result is a collision between two continents,which cause the formation of complex mountains such as the Himalayas in SOuth americaOcean-when two oceanic slabs coverage one descends beneath the other,causes volcanic activity Transform-transform fault boundaries are margins where two plates grind past eachother without the production or destruction of lithosphere
 What is the driving force of the plate tectonics ?
 Convection occurring in the mantle is the basic driving force for the plate movement
 What are hotspots ?
 A concentration of heat in the mantle capable of producing magma,which rises to Earths surface
 What are some evidence of plate tectonics ?
 PaleomagnetismEarthquake patternsOcean driftingHot spots