What happened 4.2 billion years ago?

Hadean eon represents the first eon in the geological time scale. It was right from the time of formation of the earth i.e from about 4.5 to 4 billion years back. It is the time when the earth was started to form undergoing heavy bombardments from the asteroids and other matters from the solar system. The impact mechanism was severe then and the overall temperature of the earth was very high. These materials then slowly started accreting to form the earth. The rocks of this eon are found to be present in some parts of Greenland, Australia, and Canada. The materials that accumulated on earth from the space were comprised of a significant amount of water that is still present today. The moon also is predicted to form during this period due to the collision between the earth and an asteroid. Life was absent during this eon.

they are known to reach a speed of 21 miles per hour

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