Snowball Earth describes a theory that for millions of years the Earth was entirely smothered in ice, stretching from the poles to the tropics. This freezing happened over 650 million years ago in the Pre-Cambrian, though it's now thought that there may have been more than one of these global glaciations. They varied in duration and extent but during a full-on snowball event, life could only cling on in ice-free refuges, or where sunlight managed to penetrate through the ice to allow photosynthesis.
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.
Runaway ice sheet growth could lock the planet into a vicious circle of freezing.
Russian climatologist, Mikhail Budyko calculated that Earth's climate has a theoretical break point. Too much ice could trigger a global freeze cycle. 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.
Slow-freezing, glass-clear ice enabled pockets of life to survive on Snowball Earth.
Chris Mckay of NASA investigates a particular kind of ice whose properties enabled life to survive on Snowball Earth. 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.
The snowball Earth hypothesis posits that the Earth's surface became entirely or nearly entirely frozen at least once, some time earlier than 650 Ma (million years ago). Proponents of the hypothesis argue that it best explains sedimentary deposits generally regarded as of glacial origin at tropical paleolatitudes, and other otherwise enigmatic features in the geological record. Opponents of the hypothesis contest the implications of the geological evidence for global glaciation, the geophysical feasibility of an ice- or slush-covered ocean, and the difficulty of escaping an all-frozen condition. There are a number of unanswered questions, including whether the Earth was a full snowball, or a "slushball" with a thin equatorial band of open (or seasonally open) water.
The geological time frames under consideration come before the sudden multiplication of life forms on Earth known as the Cambrian explosion, and the most recent snowball episode may have triggered the evolution of multi-cellular life on Earth. Another, much earlier and longer, snowball episode, the Huronian glaciation, which occurred 2400 to 2100 Ma may have been triggered by the oxygen catastrophe.
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