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 Earth orbit
 4.15 billion years ago


Precambrian Earth - Meteorite strike on infant Earth - Space Art/Natural History Illustration; Hadean eon; Pre-Archean; Pre-Cambrian, Precambrian Geologic Time Scale

Supereon: Precambrian
 Eon: Hadean
  Era: Basin Groups


Meteorite strike on infant Earth

A molten, infant Earth is impacted by an object about 10 miles in diameter, releasing 200 million times a much energy as the largest manmade explosion. While this collision appears negligible when compared to the scars of much larger encounters, a similar impact four billion years later may have resulted in the extinction of the dinosaurs.

The Earth accrued the majority of its mass during the 100 million years following the formation of the Sun, a period referred to as the cosmic bombardment. During this era of frequent impacts and radioactive heating, the entire Earth remained molten long enough for the heavy metals iron and nickel to settle to the center of the Earth while lighter silicates floated to the surface. Today, over four and a half billion years later, the Earth is still cooling. The silicates, forming a crust only a few tens of miles thick, still float on an "ocean" of molten metals and minerals, and the temperature at the center of the Earth may yet be hotter than the surface of the Sun.



Copyright Walter B. Myers. All rights reserved.

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