Snowball Earth facts for kids
Imagine a time when almost the entire Earth was covered in ice, like a giant snowball! This idea is called Snowball Earth or Icehouse Earth. It describes periods when our planet's surface was almost completely frozen.
Scientists now think it's very likely that huge ice sheets covered much of the Earth during ancient times, especially in the Proterozoic Eon (a very long time ago). What they still discuss is exactly how much of the Earth was covered.
People who support the Snowball Earth idea say it explains why we find rock layers formed by glaciers in places that used to be warm, near the tropics. These rocks also help explain other puzzling things in the Earth's history. Others aren't so sure. They question if an ocean completely covered in ice or slush could even happen.
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Ancient Ice Ages: The Palaeoproterozoic
The Earth has experienced several major ice ages. One of the earliest and most significant was the Huronian glaciation. This period happened about 2,400 to 2,100 million years ago.
The Huronian Glaciation
The Snowball Earth idea helps explain the rock layers left behind by glaciers in a part of Canada called the Huronian supergroup. Scientists have found evidence that these ice sheets might have reached very low latitudes, close to the equator.
Rocks from South Africa, called the Makganyene formation, are a bit younger. They formed around 2.25 billion years ago and also show signs of glaciers in tropical areas.
Why Did It Get So Cold?
Scientists think a big reason for this deep freeze was the rise of oxygen in the atmosphere. As oxygen increased, it might have removed a gas called methane. Methane is a powerful greenhouse gas, meaning it traps heat.
At that time, the Sun was not as strong as it is today. So, the Earth's climate might have needed methane to stay warm enough. Without this methane, temperatures could have dropped sharply, leading to a Snowball Earth event.
Later Ice Ages: The Neoproterozoic
The late Neoproterozoic Eon saw three or four important ice ages. The two biggest ones were the Sturtian and Marinoan ice ages. Both happened during the Cryogenian period.
- Kaigas ice age (825 – 730 million years ago)
- Sturtian ice age (720 – 635 million years ago)
- Marinoan ice age (650 – 635 million years ago)
The Sturtian and Marinoan Events
The Marinoan ice age was the most widespread of these events. The Sturtian glaciations were also very extensive. These two periods saw ice cover a huge part of the planet.
Another ice age, called the Gaskiers glaciation, lasted for a million years. It was very intense, but it probably didn't cover the entire globe.
The Kaigas Glaciation
The Kaigas glaciation is less clear. Some scientists don't think it was a true ice age, while others believe it was a third, less severe one. It was definitely not as big as the Sturtian or Marinoan glaciations.
Even with some questions, there's strong evidence that the Earth went through several major glaciations during the Neoproterozoic.
Images for kids
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Artist's picture of a fully-frozen Snowball Earth with no liquid water left.
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Diamictite rock from the Neoproterozoic Pocatello Formation, a type of "snowball Earth" deposit.
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Elatina Fm diamictite rock below the Ediacaran GSSP site in the Flinders Ranges NP, South Australia. An Australian dollar coin for size.
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This rock is 2.1 billion years old and contains black-band ironstone.
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A present-day glacier, similar to those that covered the Earth.
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Volcanoes might have helped bring back carbon dioxide (CO2), possibly ending the global ice age of the Cryogenian Period.
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A computer simulation showing what conditions might have been like during a Snowball Earth period.
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Global ice sheets might have created the right conditions for the evolution of complex life forms.
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A black smoker, a type of vent that releases hot water from the ocean floor.
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Dickinsonia costata, an Ediacaran organism with a quilted look. Scientists are still learning about it.
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See also
In Spanish: Glaciación global para niños
