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.
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|