Ice Ages: Glaciations in Geologic History

Ice Ages

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.

At least, this is reasonable to assume for the last ice age 10,000 years ago. Atmospheric chemistry, solar output and ocean currents can trigger ice ages.

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.

Ice Ages Timeline

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
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