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Ice Ages: Glaciations in Geologic History


Ice Ages

Our planet has experienced 5 substantial ice ages. During this time, a hefty layer of ice smothered our planet as a giant snowball. 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:

  • MILANKOVITCH CYCLE: 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.
  • ATMOSPHERE CHEMISTRY: When our atmospheric chemistry alters, it can influence temperature.
  • SOLAR RADIATION: A reduction in solar output reduces heat.
  • OCEAN CURRENTS: A swing in ocean currents can trigger ice ages.

Today, we’re going to deep-dive into the cold and explore when Earth was a giant snowball.

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 from 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 on 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

One Comment

  1. There is a major factor missing in the list of reasons “What causes ice ages”:

    Snow can only accumulate to large ice shields on land, not so much on the sea. Therefore, the continental distribution is decisive for the ice to build up and with it the ice-albedo.

    At least this is true if we look at Antarctica moving away from the south pole in the Permian era, causing the warm Mesozoic and returning back to the south pole at the end of the cretaceous, causing our current ice age.

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