That is a smart question . . . not smarter than me!!
Perhaps you mean Hadean when the planets of the solar system were just forming out of dust and particles. There were no solid rocks or anything yet, so you could hardly call it geologic.
The thing about gravity is that if two specks of dust are drifting around the sun alongside each other, they are pulled together by their own gravitational fields. The more particles get pulled together, the bigger the particles and the bigger the forces. Eventually, the particles look more like a cloud than individual particles, then a few million years later you have something that is liquid, or perhaps solid.