GEOG - Lecture 16 Review

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Texas Tech University *

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1401

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Geology

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Oct 30, 2023

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Review 16 16 Plate Tectonics 16.1 Orders of Relief Orders of Relief – - Relief – Refers to the shape of the land, especially the elevation difference between the highest and lowest part of an area - 1 st Order of Relief – Continents and oceans - 2nd Order of relief – Major features of continents and oceans - 3 rd Order of Relief – Individual landforms, such as hills, valleys, beaches 2nd Order Features of Oceans – - Ocean Ridge – Flanked by flat areas known as abyssal plains - Continental Rise – Near the continents, the floor of the ocean begin to slope gently upward. Merges into continental slope - Continental Slope – Is steeper, meets with the continental shelf - Continental Shelf – An underwater extension of the continent 2nd Order Features of Continents – - Mountain Chains – indicate active regions of either volcanism or tectonic activity - Shields – Generally very old and relatively flat o Covered Shields – If they have a cover of sediment o Exposed Shields – If the bedrock is present at the surface - Mountain Roots – Are the remains of old mountain chains in areas which are no longer active in mountain building. 16.2 Continental Drift Alfred Wegener – A German meteorologist, who argued that the continents were once together as one large landmass. He based his argument largely on the matching of rock types on the coasts of continents like South America and Africa Continental drift – The gradual movement of the continents across the earth’s surface through geological time

16.3 Plate Tectonics Paleomagnetism – Concerned with magnetism, in rocks that was induced by the earth’s magnetic filed at the time of their formation Sea Floor Spreading – Formation of new crust along the mid-ocean ridges - Crust is not getting bigger, so old material must be brought back into the mantle, and this is found to occur in ocean trenches Convection Cells in Asthenosphere – Pushes magma upward through volcanic vents and spreading centers to create new crust 16.4 Plate Boundaries Plate Boundaries – Most tectonic activity goes on near the boundaries of plates. The activity occurring is generally due to the way in which two plates meet. - Divergent – Plates are moving away from each other and new material is moving in to fill the void o Situation at mid-ocean ridges - Transform Faults – The plates slide past each other o Situation in Southern California, where the Pacific Plate is moving north relative to the North American Plate - Convergent – Three types: o Ocean-Continent Convergent – The lighter plate (continent) overrides the heavier one (oceanic), so that the oceanic plate is subducted.  Often results in volcanoes and mountains created by the crunching up of the continental plate. o Ocean-Ocean Convergent – One descends (like ocean-continent) and volcanic activity on ocean floor results.  How island arcs are formed, like the Aleutian Islands in Alaska and the Lesser Antilles in the Caribbean o Continent-Cont. Convergent – Since neither plate is composed of heavier material, the two stay on the surface and crunch up to form mountains. Pangea, Laurasia, Gondwanaland – - Pangea – Roughly 250 million years ago, all of the continents were one land mass, which broke up into separate plates which moved around to their present positions - Laurasia – First into a northern continent

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