Loudoun County Public Schools / Overview

The Earth formed approximately 4.6 billion year ago as a molten ball of rock. There was almost no atmosphere. As the Earth cooled a solid crust formed. There was a high level of volcanic activity. Volcanoes gave out mostly carbon dioxide (CO 2), steam (H 2 O), and small amounts of ammonia (NH 3) and methane (CH 4). There was little or no oxygen in the Earth’s early atmosphere. ................
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