Volcanic activity billions of years ago set the stage for Earth's oxygen-rich atmosphere, research suggests
It is widely believed that Earth's atmosphere has been rich in oxygen for about 2.5 billion years due to a relatively rapid ...
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Earth: Facts about the Blue Planet
Earth formed over 4.5 billion years ago from a swirling cloud of gas and dust squished together by gravity. That same cloud gave rise to our entire solar system, including our star, the sun.