Geo Chap 4

Geo Chap 4 - January 17, 2008 & January 22, 2008...

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Chapter 4, Page 1 Geological Catastrophes: Chapter Four Chapter Four Vocabulary: 1. Acceleration : (1) To cause to move faster. (2) The rate of change of motion. 2. Aftershock : A smaller earthquake following a mainshock on the same section of a fault. Aftershocks can continue for years following a large mainshock. 3. Amplitude : The maximum displacement or height of a wave crest or depth of a trough. 4. Base Isolation : Protecting buildings from earthquakes by isolating the base of the building from the shaking ground via rollers, shock absorbers, etc. 5. Body Wave : Seismic waves that travel through the body of the Earth, for example, primary and secondary waves. 6. Cross Section : A two-dimensional drawing showing features in the vertical plane as in a canyon wall or road cut. 7. Dip : The angle of inclination measured in degrees from the horizontal. 8. Dip-Slip Fault : Faults where most of the movement is either up or down in response to pushing or pulling. 9. Fault : A fracture or belt of fractures where the 2 sides move past each other. 10. Footwall : The underlying side or block of a fault. 11. Foreshock : A smaller earthquake that precedes a mainshock on the same section of a fault. 12. Fracture : A general term for any breaks in rock. Fractures include faults, joints, and cracks. 13. Frequency : Number of events in a given time interval. For earthquakes, it is the number of cycles of seismic waves that pass in a second; frequency = 1/period. 14. Granite : A quartz-rich plutonic rock. 15. Hanging Wall : The overlying side or block of a fault. 16. Hertz (Hz) : One hertz (Hz) equals one cycle per second. 17. Hypocenter : The initial portion of a fault that moved to generate an earthquake. Hypocenters are below the ground surface; epicenters are placed above them on the surface. 18. Inertia : The property of matter by which it will remain at rest unless acted on by an external force. 19. Joint : A fracture or parting in rock. 20. Law of Original Continuity : A water-laid sediment body continues laterally in all directions until it thins out due to nondeposition or butts against the edge of the basin of deposition. 21. Law of Original Horizontality : Sediments are deposited in nearly horizontal layers. 22. Law of Superpostion : In a sequence of sedimentary rock layers, the oldest layer is at the base, and ages are progressively younger toward the top. 23. Left-Lateral Fault : A strike-slip fault where most of the displacement is towards the left hand of a person straddling the fault. 24. Magnitude : An assessment of the size of an event. Magnitude scales exist for earthquakes, volcanic eruptions, hurricanes, and tornadoes. For earthquakes, different magnitudes are calculated for the same earthquake when different types of seismic waves are used. 25.
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Geo Chap 4 - January 17, 2008 & January 22, 2008...

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