1.90-0.80 billion tears ago : The Formation of a Supercontinent. 700-600 million years ago : The Sturtian Glaciation 700-600 million years ago : The Leaking Earth. Free oxygen produced by cyanobacteria gradually accumulated in the atmosphere. When the soil covered the dead cyanobacteria, more oxygen accumulated and atmospheric oxygen dramatically increased. “The Leaking Earth" phenomenon that started about 700 million years ago further expanded both the land, and free oxygen in the atmosphere, resulting in the expansion of the habitat of life that led to explosive biological evolution.