The Precambrian time was the first period of earth. This was 4.5 billion years ago. During this time there were only one celled organisms. It was the time when earth was not formed and had no crust. It was just molten lava. The outer covering hardens into the crust. The crust from volcanoes. The clouds around the volcanoes pour heavy heavy rain cause oceans. When the crust cooled making huge pieces of crust began to move causing tectonic plates. The very first continent was huge it was called the Rhodinia. It formed about 1.1 billion years ago. It contained North America, Australia, Antarctica, and South America. About 350 millions later the first ocean was formed breaking up this continent and making the supercontinent. The only life forms that roamed the earth back then were one-celled organisms called cyanobacteria. These organisms contributed to earth by giving it oxygen so when us humans come along we will have good living conditions.