What is the Archaean Period?
The Archaean Period lasted from 3800 to 2500 million years ago. The Earth was still about three times as hot as it is today, and most of its area was covered with oceans. The Earth’s atmosphere was mainly carbon dioxide, with very little oxygen in it. Land was beginning to form as volcanoes that emerged from the oceans. The forming of the continents also began during this period, probably as lava flow under the ancient oceans.About this time, the earliest living cells formed on Earth. These cells all lived in the oceans. One type of bacteria present then was the cyanobacteria, or blue-green algaes. These bacteria appear to have had a very strong cell-wall, and the ability to form layers in the ancient sediments. The formations are called stromatolites. They can be found in Archaean rock formations of Western Australia.So to sum up, the Archaean Period was a time of continent-building, and the first stages of early life can be traced back to this period.
Raising Rocks
Do you know why you sometimes find sea shells on top of rocks? It is because most sedimentary rocks were once found under the sea. Animals that were buried in the sediment became fossilized. Later, movements of the Earth’s crust resulted in the sea bed being pushed upward, and rocks that had been under the sea now became mountain tops.