Chapter19rev - Chapter 19 review Christian Smith 1 Between...

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Chapter 19- review Christian Smith 1. Between 5 and 6 billion years ago, a very dense, collapsed star exploded and dispersed matter throughout the volume of the present-day solar system. This matter formed a disk-shaped cloud that began to rotate and contract gravitationally. A protosun grew from a concentration of matter at the center of the disk; eventually it grew large enough to support thermonuclear reactions and the Sun was born. Eddylike, swirling movements in the rotating disk produced local concentrations of the dispersed matter and promoted growth of small planetoids. Continued growth led to larger gravitational forces and even more collisions and impacts until most of the dispersed matter was collected into a few, remaining, massive protoplanets. 2. Green plants. 3. Precambrian history is more difficult to decipher because of the lack of fossils, which hinders correlation of rocks. Also, rocks of this great age are metamorphosed and deformed, extensively eroded, and obscured by younger overlying strata.
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  • Spring '13
  • NguyenVanVuong
  • Geological history of Earth

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