Ice Ages: Glaciations in Geologic History
Once upon a time, Earth was a giant snowball. Our planet has experienced 5 substantial ice ages. During this time, a hefty layer of ice smothered our planet.
It was unimaginably frigid at this time where temperatures dropped to 5°C to 10°C lower than it is today.
Ice ages happen for several reasons. In the eyes of Milankovitch, Earth is prone to ice ages because of how its cyclical movements affects climate.
The History of Ice Ages on Earth
Throughout Earth’s history, it’s experienced drastic shifts in temperature. During warm periods, global mean temperatures were 8°C to 15°C warmer than it is today. Polar areas were so warm that they were free from ice.
But during extended cold periods, global temperatures plummeted 5°C to 10°C on average which started an ice age. These are long periods of cooling where continents repeatedly endure glacial and interglacial periods. Earth has sustained 6 major ice ages.
What causes ice ages?
Greenhouse gases have a warming effect in the atmosphere. If you reduce the amount of atmospheric carbon dioxide (CO2), then this creates an environment suitable for glaciation.
For example, the Great Oxygenation Event was a time when early Earth was getting filled with oxygen. But when oxygen combines with methane, it releases carbon dioxide.
Methane is a remarkably effective greenhouse gas and traps heat in the atmosphere. Because there was less methane in the atmosphere at this time, the greenhouse effect trapped less heat in the atmosphere.
This sparked temperatures to plummet creating a global ice age. Other factors can disturb the carbon cycle as well. For example, accumulations of organic carbon in the ocean can drastically shift climate.
What ice ages occurred in Earth’s history?
|Ice Age||Duration||Geologic Time Period|
|Pongola||2.9 – 2.8 billion years ago||Archean|
|Huronian||2.4 – 2.30 billion years ago||Proterozoic|
|Cryogenian||715 – 547 million years ago||Proterozoic|
|Andean-Saharan||450 – 420 million years ago||Paleozoic|
|Karoo||360 – 260 million years ago||Paleozoic|
|Late Cenozoic||34 – Present||Cenozoic|