History of the Earth

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History of the Earth Geology is the study of the Earth, so what better topic to choose than the History of the Earth. The Earth formed around 4.5 billion years ago which means that the Earth has a great deal of history. Mostly all topics in Geology relate to History in one way or another. The earth was formed due to a solar nebula, although it had no oxygen and could not support humans or other modern life. At this time much of Earth was molten due to volcanoes and collisions with other bodies. One very large collision is thought to have caused the Earth to tilt at an angle that formed the moon. After time the planet cooled forming a solid crust which allowed water to exist on the surface. The first life forms appeared about 3.5 billion years ago and the first photosynthetic life forms appeared about 2 billion years ago which in turn enriched the atmosphere with oxygen. Life remained this way, mostly small and microscopic until about 580 million years ago. This period, known as the Cambrian period, is when the Earth experienced rapid diversification into most major phyla. The history of the Earth can be organized chronologically in a table called the geological time scale. This table splits the geological time into intervals based on stratigraphic analysis. This table is used to describe the relationships between events that have occurred throughout Earth’s history. The largest unit of time is the supereon which is composed of eons. Eons are then divided into eras. Eras are then divided into periods, epochs, and ages. The terms eonothem, erathem, system, series, and stage are used to refer to the layers of rock that correspond to these periods of geologic time in earth's history. Geologists qualify these units as Early, Mid, and Late when referring to time, and Lower, Middle, and Upper when referring to the corresponding
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