glaciation

It started with a period of glaciation that must have been a chilly change from the greenhouse-like Oligocene, and ended with a prolonged period of glaciation, too.

Subsequent glaciations continued their erosion, giving many canyons within the structure their present distinctive shape.

Yet efforts to explain what initiated these periods of global glaciation, which have come to be known as "Snowball Earth" events, have been inconclusive.

The project was inspired by the glacial debris left by the ancient glaciation from this period that can be spectacularly observed in the Flinders Ranges in South Australia.

Earth’s glaciation, they say, may have come from a global drop in carbon dioxide emissions, a result of fewer volcanoes expelling the gas into the atmosphere.