asttesttworeview - LAYERS OF THE EARTH There are three main...

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LAYERS OF THE EARTH There are three main layers of the Earth: (1) relatively thin, rocky crust (2) thick silicate mantle of hot plastic rock (3) dense core-composed mainly of iron; liquid outer core (huge), solid crystalline inner core (small) By careful mapping of the patterns of many earthquakes that travel to different depths, seismologists have peeled away the Earth’s outer layers and looked at various levels within it. o This is due to the different ways rock layers of different density and stiffness propagate the waves at different speeds. o The Earth’s internal structure is determined by the varying velocity of earthquake waves. (two kinds: push-and-pull, shake) CONTINENTAL DRIFT Two major types of terrain on Earth: high, dry continents and low, wet floor oceans Wegner came up with the theory of moving continents. He based his concept of continental drift not only on the similar shapes of the present continental edges but also the striking match of certain rocks, geological formations, fossils along the borders of continents on opposite sides of the Atlantic. Concluding that, all the continents were once, 200 million years ago, part of a single landmass, Pangea, that drifted apart due to plate tectonics. Sea floor spreading: new sea floor is forced at a rift in the mid-ocean ridge, turning cold and heavy as it spreads away from its source in two directions; the sea floor eventually sinks and disappears in a deep-ocean trench, where it is consumed, Its material is then recycled and born again as new floor emerges from the ridge. The continents are implanted with moving plates, driven by heat from below, and continental drift is a consequence of the motion of plates carried along by the sea- floor spreading. The effects of continental drift account for most of our world’s familiar surface phenomena, such as mountains, earthquakes and ocean basins. OZONE The ozone layer is created by the sun’s ultraviolet rays The ozone layer is a layer of O3, which blocks radiation from the Sun. It protects us by absorbing most of the Sun’s ultraviolet emission and keeping its destructive rays from reaching the ground. If there were no ozone shield, plants, animals, and humans could not even exist on the land. We punch holes through the ozone layer with chemicals used in our everyday
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This note was uploaded on 03/31/2008 for the course GOV 310K taught by Professor V during the Spring '08 term at University of Texas.

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asttesttworeview - LAYERS OF THE EARTH There are three main...

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