Chapter 1 - An Overview of Our Planetary Environment

Chapter 1 - An Overview of Our Planetary Environment -...

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Chapter 1 - An Overview of Our Planetary Environment Environmental Geology - study of the interactions between humans and their geologic environment. Earth In Space And Time o The Early Solar System Most Astronomers accept some sort of "Big Bang" as the origin of today's universe Stars formed from the debris of the Big Bang Our sun and its system of circling planets, including the earth, are believed to have formed from a rotating cloud of gas and dust, some of it from debris from older stars. The dust clumped into planets, the formation of which was essentially complete over 4,500,000,000 years ago. o The Planets The composition of plants formed depended largely on how near they were to the hot sun. Planets formed nearest to the sun contained mainly metallic iron and a few minerals with very high melting points, with little water or gas. Further out, planets incorporated much larger amounts of lower-temperature minerals, including some that contain water locked within their crystal structures Made it possible for earth to have liquid water at it's surface Farther from the sun, temperatures were so low that nearly all of the materials in the original gas cloud condensed The result was a series of planets with a variety of compositions, most quite different from the earth. o Earth, Then and Now The early earth was heated by the impact of the colliding dust particles and meteorites as they came together to form the earth, and by the energy release from decay of the small amounts of several naturally radioactive elements. These heat sources combined to raise the earth's internal temperature enough that parts of it melted. Metallic iron, would have tended to sink toward the middle of the earth. As cooling progressed, lighter, low-density materials crystallized and floated out toward the surface.
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Core - innermost zone of the earth; composed largely of iron. Made up mostly of iron, with some nickel and a few minor elements Mantle - zone of the earth's interior between crust and core; rich in ferromagnesian silicates. Made up mainly of iron, magnesium, silicon, and oxygen combined in varying proportions in several different minerals Crust - outermost zone of earth; composed predominately of relatively low-density silicate minerals Has everything The heating and subsequent differentiation of the early earth led to another important result: formation of the atmosphere and oceans. Many minerals had contained water, and as the earth's surface cooled, the water condensed to form the oceans. The early atmosphere was quite different than the modern one It contained little of no oxygen in it, instead it consisted dominantly of nitrogen and carbon dioxide with minor amounts of such gases as methane, ammonia, and various sulfur gases. o
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Chapter 1 - An Overview of Our Planetary Environment -...

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