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Chapter 2

Chapter 2 Notes

11 Pages

Environmental Science
Course Code
Nick Eyles

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Chapter 2 PLATE TECTONICS What is Plate Tectonics? -tectonics: the study of the origin and arrangement of the broad structural features of the Earths surface, including not only folds and faults, but mountain ranges, continents, & earthquake belts -plate tectonics: the earths surface is divided into several large, thick plates that move slowly and change in size; intense geologic activity occurs at plate boundaries -concept was developed in the late 1960s by combining continental drift & sea floor spreading theories -continental drift: idea that continents move freely over earths surface, changing their positions relative to each other -sea floor spreading: idea that the sea floor forms at the crest of mid- oceanic ridges, then moves horizontally away from the ridge crest toward an oceanic trench How Did the Plate Tectonics Theory Evolve? The Early Case for Continental Drift -ideas been around for 130 years -Alfred Wegener -noted in early 1900s that SA, Africa, India, Antarctica, & Australia all had almost identical Paleozoic rocks & fossils Scepticism About Continental Drift -people didnt believe Wegener at first because they thought that rocks were much too strong to be able to move about and crumple mountains, etc www.notesolution.com-the driving mechanism he proposed was a combination of centrifugal forces that causes tides -therefore in the northern hemisphere, they didnt believe him because they thought the force wasnt strong enough -more support in the southern hemisphere where the rocks were matching other places Renewed Interest in Continental Drift -because of 1) study of the sea floor & 2) geo research in relation to rock magnetism Study of the Sea Floor -oceans cover more than 70% of earth -rock dredge: rocks are taken from sea floor by being broken off by a dredge, an open steel container dragged along -corer: used to sample sediments from the sea floor -single- beam echo sounder: measures water depth & draws profiles of submarine topography -sidescan sonar: measures the intensity of sound reflected back to the tow vehicle from the ocean floor and provides detailed images of the sea floor & info about bedforms & sediments -seismic reflection profiler: works on pretty much same as above but uses a louder noise @ lower frequency Geophysical Research -inclination of the magnetic alignment preserved in the magnetite minerals in the lava flows can be used to determine the paleolatitude at which the flow formed -paleomagnetism: study of ancient magnetic fields -polar wanderings are now used to reconstruct continental movement over time www.notesolution.com
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