Geology Notes for Midterm

Geology Notes for Midterm - Chapter 3: Plate Tectonics and...

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Unformatted text preview: Chapter 3: Plate Tectonics and Earthquakes 01:13- Earthquakes more common at transform faults & subduction/collision zones- Tectonic cycle: grand recycling of outer layers of Earth- Oceanic ridges: mountain ranges of volcanoes- Evidence of plate tectonics concept magnetization patterns of sea floors earthquake epicenters outline plates deep earthquakes oceanic mountain ranges and deep trenches systematic increases in seafloor depth fit of continents oldest rocks/fossils in ocean basin are less than 5% of Earths age, indicating that oceanic material is destroyed by recycling into the mantle- Spreading Centers/Divergent : (pull-apart) The expanded volumes of warm rock in the oceanic ridge systems have a higher heat content and a resultant decrease in rigidity. These heat-weakened rocks dont build up and store the huge stresses necessary to create great earthquakes. Moderate earthquakes Iceland Red Sea and Gulf of Aden o Rift valley o Triple junction- Collision/Convergent Zones Greatest earthquakes o Oceanic plate vs. oceanic plate o Oceanic plate vs. continent o Continent vs. continent The biggest disasters are from the great earthquakes that occur at shallow depths and concentrate their energy on the surface Seismic-gap method : (for forecasting earthquakes) if segments of one fault have moved recently, then it is reasonable to expect that the unmoved portions will move next and thus fill the gaps Subduction Zones o Indonesia (2004, 2005) Indian-Australian plate Himalayas o Tokyo (1923) Continent-continent collisions o Pakistan and India (2001, 2005) o Shaanxi Province, China (1556) o Tangshan, China (1976) T ransform Faults (slide-past motion) Large earthquakes Turkey (1999) o North Anatolian fault San Andreas Fault Arabian Plate o Iran (1962-2005) o Dead Sea fault zone Chapter 4: Earthquake Geology and Seismology 01:13- Earthquake: The sudden slip on a fault (release of elastic energy), and the resulting ground shaking and radiated seismic energy caused by the slip Chapter 4: Earthquake Geology and Seismology 01:13- Fault : a fracture (crack) in the earth, where the 2 sides of the earth move past each other. - Stresses: build up in near-surface rocks until the stress is so great that the rocks fracture and shift along a fault- Types of Plate Boundaries & Stress Convergent = Compressional Stress Divergent = Extensional Stress Transform = Shear Stress- Types of Faulting & Stress Thrust/Reverse Faulting = Compressional stress Normal Faulting = Extension Strike-Slip Faulting = Shear- Fault Geometry (draw) dip: angle of inclination from horizontal of tilted layer (or fault surface) strike: compass bearing of horizontal line in tilted layer- Types of Faults : (defined by their sense of motion) Dip-slip (normal or reverse thrust) Strike-slip (left or right lateral) Oblique (both strike and dip components of slip)- Faults: complex zones of breakage with irregular surfaces, many miles wide and long Chapter 4: Earthquake Geology and Seismology...
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This note was uploaded on 03/01/2009 for the course GEOL 20 taught by Professor Steidl during the Winter '08 term at UCSB.

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Geology Notes for Midterm - Chapter 3: Plate Tectonics and...

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