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Geology Ch. 10
| Question | Answer |
|---|---|
| Drawbacks of Richter Scale | Is inaccurate in measuring strength of large earthquakes |
| 10X increase | |
| Shearing Effect | When an earthquake happens it breaks the ground up. |
| Wriggling Effect | |
| Earthquake | Trembling of ground caused by sudden release of energy in underground rocks |
| Location of most earthquakes | Near plate boundaries where there is the greatest stress |
| Strain Energy | Stress that builds up in rocks |
| focus | Subterranean spot where rocks rupture / shift |
| All catastrophic quakes are within this distance of the focus | Forty miles |
| Epicenter | Point on Earth's surface directly above focus |
| After shock | Rocks continuing to shift well after earthquake |
| Richter Scale | Based on seismograph readings of magnitude-correlates amplitude with energy |
| Seismic Waves | Waves that transmit released energy |
| Seismograph | Machine that determines magnitude of earthquake |
| Seismology | Study of earthquakes and Earth's interior |
| Seismograms | Visual record of seismograph-records time and magnitude |
| Time and Magnitude | Measurements of earthquakes by seismographs |
| Body Waves | Transmit energy through Earth's interior |
| P - Waves | Primary waves |
| Which waves are the fastest? | P-Waves |
| Compressional | Primary waves (P-waves) |
| Waves that move like springs or slinkys | Movement of P-Waves / jolting action |
| S - Waves | Secondary Waves |
| Speed of Waves | P - waves = fastest waves. S - waves = slower than P waves, Surface waves = slowest |
| How do S - waves move? | Perpendicular to direction of wave |
| Surface waves | Side to side and rolling motion |
| Where is the energy of surface waves found? | Along the surface |
| Which wave is responsible for the most damage to rigid structures? | Surface waves |
| Strength of Earthquakes | Depends on how much energy is released |
| Mercalli Intensity Scale | Reports of damage based on eyewitnesses |
| Moment-Magnitude Scale | More accurate on Large earthquakes |
| What does the Moment-Magnitude Scale measure? | Measures the cause rather than the effect- more accurate on large earthquakes |
| Locating epicenter | Since P & S waves travel at different speeds, the difference between their arrival time can be used to calculate distance from epicenter |
| How is the epicenter marked on a map? | Circles radiation from the center |
| How many measurements must be made from different locations to triangulate the exact epicenter of an earthquake? | Three |
| Ground displacement | Large scale shifting of landscape |
| What was the ground displacement in the 1906 San Francisco earth quake? | 25 feet surface shift |
| What was the ground displacement in the 1964 Alaska earthquake? | 39 feet vertical shift |
| Landslide | Masses of loose rock combined with soil suddenly fall down a slope. |
| Liquefaction | Vibrations increase water pressure between soil particles transforming them into a slurry of mud |
| What happened to Port Royal, Jamaica in 1692 | Slid into the sea |
| Seiches | Water sloshing back and forth in a basin |
| Kenai Lake , Alaska 1964 | Rose 30 ft. on one end |
| Tsunami | Enormous sea waves caused by rapid displacement of ocean floor associated with submarine earthquakes |
| Location of 80% of earthquakes | Pacific rim where ocean plates sub-duct |
| 20% of earthquakes occur here | In collision zones running through southern Europe and southern Asia |
| Oceanic divergent zones | Shallow - 12 miles |
| Depth of Continental Drift, Collision zones, and Transform boundaries | 30 to 65 miles, slightly deeper than oceanic divergent zones |
| Subduction zones | Down over 400 miles |
| At which depth do we find the most powerful Earthquakes? | Shallow and intermediate depths |
| At what level will quakes occur when they occur further inland? | A deeper level. |
| Depth of interplate earthquakes | Occur 30 miles down, have lower magnitude, but are felt over wider area |
| Causes of interplate earthquakes | No know cause |
| What can civilization do to minimize damage from earthquakes | Educate public about the risk, improve building codes to minimize damage |
| Examples of improved building codes in know earthquake areas | Use reinforced and flexible materials that flex with quake, build on beadrock |
| The best defense against earthquakes | Predictions of future earthquakes, study history of, know location of seismic gaps |
| Seismic gaps | An area along a fault where relatively few earthquakes have occurred recently but where strong earthquakes occurred in the past |
| Short predictors of earthquakes | cracking in rocks called expansion, Fore shocks, bulges, and changes in seismic velocity |
| Dilatancy Producing Foreshocks | Cracking in rocks due to expansion |
| Other predictors of earthquakes occurrences | Unusual animal activity, animals hear the cracking within the earth |
| What has man studied to learn about the composition of Earth's interior? | Seismic waves |
| What has man learned by studying seismic waves? | Density, thickness, composition, structure and state of Earth's interior |
| The variation in speed of seismic waves indicate... | Composition, structure, temperature and pressure differences of the Earth's interior |
| This accelerates when traveling through solids and slows when traveling through fluids | P Waves |
| If S waves disappear when passing through fluids. What happens when they pass through solids? | They appear and can be studies |
| What do both P waves and S waves do at boundaries of plates? | If they are strong enough, they keep going and might meet at the other side of the globe |
| How many layers make up the Earth? | Three |
| What is the name of the first layer of the Earth? | Crust |
| What is the name of the second layer of the Earth? | Mantle |
| What is the name of the third layer of the Earth's interior? | Core |
| What is the Earth's crust composed of? | Silicate and igneous rock |
| Name the layers that compose the Earth's crust. | Continental and oceanic |
| What is the composition and thickness of the continental portion of the Earth's crust? | Relative thick - granite, 12 - 45 miles thick |
| What is the composition and thickness of the oceanic portion of the Earth's crust? | Relatively thin - basaltic, 1 - 4 miles thick |
| Moho | Boundary between base of crust and top of mantle |
| Mantle | Covers 80% of Earth's volume |
| How deep is the mantle? | 1800 miles |
| What does the mantle consist of | Dense mafic silicates |
| Upper mantle | Composed of a uniform layer of peridotite |
| What layer is below the upper mantle? | Lithosphere |
| Description the Lithosphere | 60 miles thick, brittle |
| What is the name of the layer found below Earth's lithosphere? | Asthenosphere |
| Describe the asthenosphere | 150 miles thick, molten magma |
| Describe the lower mantle | 200 miles thick, solid transition zone |
| Center of mantle | Earth's core ? |
Created by:
sudokken
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