A succession of incredibly harsh ice ages waxed and waned during the Cryogenian. It is nicknamed Snowball Earth as it's been suggested that the glaciation was so severe it may even have reached the equator. Life during the Cryogenian consisted of tiny organisms - the microscopic ancestors of fungi, plants, animals and kelps all evolved during this time.
Began: 850 million years ago
Ended: 635 million years ago
Scientists always agreed on one ice age truth, the tropics cannot freeze... or can they?
Dropstones show that the relentlessly hot deserts of Namibia were once covered in ice. Geologists Paul Hoffman and Dan Schrag investigate. This programme was first shown in 2001.
Massive ice sheet melt created violent climate change and unleashed Earth's elemental powers.
Snowball Earth was ended by incredibly violent climate change. Paul Hoffman and Dan Schrag explain the science behind this. This programme was first shown in 2001.
Snowball Earth may inadvertently have accelerated evolution by reducing competition.
Snowball Earth may inadvertently have accelerated evolution. Biologist Guy Narbonne explains how. This programme was first shown in 2001.
During this period the following extinction level events are thought to have occurred.
The Cryogenian (from Greek cryos "cold" and genesis "birth") is a geologic period that lasted from 850 to 635 million years ago. It forms the second geologic period of the Neoproterozoic Era, preceded by the Tonian Period and followed by the Ediacaran.
The Sturtian and Marinoan glaciations, which are the greatest ice ages known to have occurred on Earth, occurred during this period. These events are the subject of much scientific controversy.
The main debate contests whether these glaciations covered the entire planet (the so-called 'Snowball Earth') or if a band of open sea survived near the equator (termed 'slushball Earth').
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