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GOL 105 EXAM 2 REVIEW CHAPTER 8: PLATE TECTONICS I. Evidence for Continental Drift (Wegener) A. Continents fit together to make Pangaea B. Fossils match up: Mesosaurus, present-day organisms C. Rock types and structures match D. Ancient climates: evidence for glaciers on tropical continents II. Plate Tectonics A. Plate Tectonics was discovered by oceanic ridge system B. Earth’s Plates i. Lithosphere is broken into pieces called plates ii. Lithosphere overlies a weaker region, asthenosphere iii. Lithospheric plates move ~5cm per year C. Plate Boundaries i. Divergent: Move apart ii. Convergent: Together iii. Transform (fault): Slide past each other III. Divergent Boundaries A. Oceanic ridges, seafloor spreading i. Older it is, the greater its thickness B. Continental rifting: begins with a formation of an elongated depression i. Sometimes becomes an outlet to the ocean IV. Convergent Boundaries A. Subduction: denser plate subducts i. Oceanic lithosphere: greater density ii. Continental lithosphere: lower density B. Oceanic-Continental Convergence i. Partial melting: melting of downgoing slab is not complete; only the lower-temperature minerals melt and rise up 1. Partial melting of mantle generates basaltic magma ii. Andesitic: basaltic magma assimilates with crustal rocks to form a silica-rich magma iii. Continental volcanic arcs: mountains that are produced by volcanic activity associated with subduction of the oceanic lithosphere C. Oceanic-Oceanic Convergence i. One descends, water is squeezed from the subducting oceanic lithosphere and melts the mantle rock above ii. Volcanic island arc: arc-shaped chain of small volcanic islands
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iii. Most volcanic island arcs are located in the western-Pacific. The subducting Pacific crust is relatively old and dense and sink into the mantle at a steep angle, which means there are not many large earthquakes iv. Only two volcanic island arcs are located in the Atlantic v. Relatively young island arcs are simple; older island arcs are more complex with crust that ranges in thickness from 20 to 35 km D. Continental-Continental Convergence i. Example: India collided into Asia and produced the Himalayas ii. Before continental collision, the landmasses are separated by an ocean basin. The seafloor between is subducted. This folds and deforms the accumulation of sediments and sedimentary rocks along the continental margin. New mountain range is composed of deformed and metamorphosed sedimentary rocks, fragments of the volcanic arc, and slivers of oceanic crust V. Transform Fault Boundaries A. Most transform faults join two segments of an oceanic ridge B. Fracture zone: prominent linear breaks in the oceanic crust; include active transform faults and inactive extensions into the plate interior VI. Evidence for the Plate Tectonics Model A. Ocean Drilling: Deep Sea Drilling Project; youngest oceanic crust found at the ridge crest and the oldest oceanic crust found near the continental margins i.
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This note was uploaded on 04/09/2008 for the course GOL 105 taught by Professor Ivany during the Spring '08 term at Syracuse.

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