What is an Ice Age?
An ice age is a period in Earth’s history in which the ice cap at the poles expanded dramatically as the Earth’s global temperature dropped. During these periods, the lands of North America and Northern Europe were covered with huge fields of ice and glaciers.
How do Scientists know about Ice Ages?
Scientists have figured out when past ice ages might have occurred by studying the earth’s geology. There are many geological features in Northern Europe and North America that can only be explained by the movement of giant glaciers. Scientists also study chemicals in the rock and fossil evidence to determine when ice ages occurred.
Are we living in an Ice Age?
Yes, you may be surprised to learn that we are currently living in an ice age called the Quaternary Ice Age. The Earth is in a warmer phase of an ice age known as the interglacial period.
Glacial and Interglacial Periods
There are periods in the glacial period that scientists define as glacial and interglacial.
Glacial – A glacial period a cold period in which glaciers were expanding.
Interglacial – An interglacial period is a warm period when glaciers can retreat.
Five Major Ice Ages
Over the course of millions of years, scientists believe that the Earth has experienced at least five major ice ages.
Huronian – The Huronian Ice Age was one of the longest ice ages in Earth’s history. It lasted about 2400 to 2100 million years ago. Scientists believe this may be due to a lack of volcanic activity that reduces carbon dioxide in the atmosphere.
Cryogenian – The Cryogenian Ice Age occurred between 850 and 635 million years ago. It is possible that the ice caps have reached the equator. Scientists sometimes call this the “Earth snowball”.
Andean-Saharan – The Andean-Saharan Ice Age occurred between 460 and 430 million years ago.
Karoo – The Karoo Ice Age lasted about 100 million years from 360 to 260 million years ago. It is named after the ice sheets in Karoo, South Africa, which scientists believe grew during this ice age.
Quaternary – The most recent Ice Age was the Quaternary Ice Age. By scientific definition, we are currently in the interglacial phase of this ice age. It started about 2.5 million years ago and is still ongoing.
What can cause an Ice Age?
The earth is constantly undergoing change. These changes could have an impact on the global climate. Some of the changes that could affect the ice age include:
Earth’s orbit – Changes in Earth’s orbit (known as Milankovitch cycles) can cause the Earth to move closer to the Sun (hotter) or farther away (colder). Ice ages could happen when we are farther from the Sun.
Sun – The amount of energy produced by the Sun also varies. Weak energy production cycles could help create ice ages.
Atmosphere – Low levels of greenhouse gases like carbon dioxide can cause the Earth to cool leading to an ice age.
Ocean currents – Ocean currents can have a major impact on Earth’s climate. Changes in flow can cause ice caps to form.
Volcanoes – Volcanic activity can release large amounts of carbon dioxide into the atmosphere. The absence of volcanoes can cause ice ages. Increased volcanic activity could also end an ice age.
Interesting Facts about Ice Ages
The current ice age in which the Earth finds itself is called the Holocene.
Most of Canada was covered in ice just 20,000 years ago.
An ice age could happen if global temperatures drop only a few degrees over a long period of time.
Ice and snow can reflect the sun’s rays and energy, further reducing temperatures and extending the duration of ice ages.
Mammals from the last ice age that are now extinct include woolly mammoths and saber-toothed cats.