Aya Alygeo chapter 12

Aya Alygeo chapter 12 - Professor Ohan Chapter 12 1)...

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Professor Ohan Chapter 12 1) Gravitation, or gravity, is a natural phenomenon in which objects with mass attract one another. In everyday life, gravitation is most familiar as the agent that gives weight to objects with mass and causes them to fall to the ground when dropped. Gravitation causes dispersed matter to coalesce, thus accounting for the existence of the Earth, the Sun, and most of the macroscopic objects in the universe. 2) Gravitation is responsible for keeping the Earth and the other planets in their orbits around the Sun; for keeping the Moon in its orbit around the Earth; for the formation of tides; for natural convection, by which fluid flow occurs under the influence of a density gradient and gravity; for heating the interiors of forming stars and planets to very high temperatures; and for various other phenomena observed on Earth. 3) In geology, the crust is the outermost solid shell of a rocky planet or moon, which is chemically distinct from the underlying mantle. The crusts of Earth, our Moon, Mercury, Venus, Mars, Io, and other planetary bodies have been generated largely by igneous processes, and these crusts are richer in incompatible elements than their respective mantles. 4) The crust of the Earth is composed of a great variety of igneous , metamorphic , and sedimentary rocks. The crust is underlain by the mantle . The upper part of the mantle is composed mostly of peridotite , a rock denser than rocks common in the overlying crust. The boundary between the crust and mantle is conventionally placed at the Mohorovičić
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discontinuity , a boundary defined by a contrast in seismic velocity. Earth's crust occupies less than 1% of Earth's volume. 5) The oceanic crust of the sheet is different from its continental crust . The oceanic crust is 5 km (3 mi) to 10 km (6 mi) thick and is composed primarily of basalt , diabase , and gabbro . The continental crust is typically from 30 km (20 mi) to 50 km (30 mi) thick, and is mostly composed of slightly less dense rocks than those of the oceanic crust. Some of these less dense rocks, such as granite , are common in the continental crust but rare to absent in the oceanic crust. Both the continental and oceanic crust "float" on the mantle. Because the continental crust is thicker, it extends both above and below the oceanic crust, much like a large iceberg floating next to smaller one. (The slightly lighter density of felsic continental rock compared to basaltic ocean rock also contributes to the higher relative elevation of the top of the continental crust.) Because the top of the continental crust is above that of the oceanic, water runs off the continents and collects above the oceanic crust. The continental crust and the oceanic crust are sometimes called sial and sima respectively. Due to the change in velocity of seismic waves it is believed that on continents at a certain depth sial becomes close in its physical properties to sima and the dividing line is called The Conrad Discontinuity
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This note was uploaded on 02/05/2012 for the course GEOLOGY 101-101 taught by Professor Ohan during the Spring '11 term at CUNY City.

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Aya Alygeo chapter 12 - Professor Ohan Chapter 12 1)...

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