GSU GEOL 1122K - Chapter 8 Textbook Annotations (21 pages)

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Chapter 8 Textbook Annotations



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Chapter 8 Textbook Annotations

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Pages:
21
School:
Georgia State University
Course:
Geol 1122k - Introductory Geosciences Ii

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Chapter 8 Textbook Annotations 217 250 8 1 Introduction o Japan lies along a convergent plate boundary where the Pacific Plate sinks back into the mantle underneath the edge of the Eurasian Plate The boundary between the two plates is a fault a large fracture on which sliding occurs that slopes gently to the west Motion along a fault doesn t happen continuously rather for many years the rocks among the fault bends to accommodate the motion o Rock can only bend so far before it snaps Shock waves are generated by the shearing and fracturing of rock along the fault When vibrations reach the land surface the land surfaces lurches back and forth and bounce up and down o Earthquake an episode of ground shaking o The societal calamity due to an earthquake is a direct consequence of ground shaking because many buildings collapse and crush their inhabitants and debris tumbles down slopes in landslides After the earthquake the sea floor coast uplifts a massive amount of water was displaced This water moved away from the site of the earthquake in immense waves called tsunamis o Earthquakes have affected the Earth since the solid lithosphere formed Most are a consequence of plate movement they punctate each step in the growth of mountains drift of continents and the opening and closing of ocean basins Almost 1 million detectable earthquakes happen every year o Most cause no damage or casualties because they are too small or they occur in unpopulated areas A few hundred earthquakes per year rattle the ground sufficiently to damage buildings and injurie their occupants and every 5 to 10 years a great earthquake occurs 8 2 What Causes Earthquakes o Ancient cultures explanations for seismicity earthquake activity most of which involved the action or mood of an animal or a god o Scientific explanations for seismicity instead occurs for The sudden formation of a new fault fracture or rupture on which sliding occurs Sudden slip on an already existing fault A sudden change in the arrangement of atoms in rock minerals Movement of magma or explosion of a volcano A major landslide A meteorite impacts An underground nuclear bomb test o Most earthquakes are due to slips on faults plate movements o The place within the earth where tock ruptures and slips or a place where an explosion occurs is the hypocenter or focus of an earthquake Energy radiates from the focus The point on the surface of the earth lies directly above the focus is the epicenter Faults in The Crust o Faults may look simply like a fracture or break that cuts across rock or sediment The rock adjacent to the fault may be broken up into angular fragments or may be pulverized into tiny grains due to the crushing and grinding that can accompany the slip and the surface of a fault may be polished and grooved as if scratched by a rasp In some localities the fault cuts through distinct marker where this



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