The beginning of the Precambrian is known as the Hadean era. The planet had just been born and it was boiling hot. Volcanoes exploded all over the place, there were constantly rocks and asteroids shooting down from space, Due to the way the solar system was created / formed and the planets were constantly crashing in to each other. Also this time period is not apart of geological history because the earth was still molten then and geological process hadn't started yet.
