Earth Science for Kids
Ice Ages
What is an ice age?
An ice age is a period in Earth's history when the ice on the polar caps significantly expanded due to an overall lowering of the Earth's global temperatures. During these periods land in North America and Northern Europe were covered by giant ice fields and glaciers.
How do scientists know about ice ages?
Scientists have figured out when past ice ages likely occurred by studying the geology of the land. There are many geological features in Northern Europe and North America that can only be explained by the movements of giant glaciers. Scientists also study the chemicals in rocks and fossil evidence to determine when ice ages have occurred.
Are we living in an ice age?
Yes, you may be surprised to know that we are currently living in an ice age called the Quaternary ice age. The Earth is in a warmer stage of the ice age called an interglacial period.
Glacial and Interglacial Periods
There are periods within ice ages that scientists define as glacial and interglacial.
- Glacial - A glacial period is a cold period when the glaciers are expanding.
- Interglacial - An interglacial period is a warm period where the glaciers may be receding.
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 the Earth's history. It lasted from about 2400 to 2100 million years ago. Scientists think it may have been caused by a lack of volcanic activity lowering the carbon dioxide in the atmosphere.
- Cryogenian - The Cryogenian ice age occurred from 850 to 635 million years ago. It is possible that ice sheets reached all the way to the equator. Scientists sometimes call this a "Snowball Earth."
- Andean-Saharan - The Andean-Saharan ice age occurred between 460 to 430 million years ago.
- Karoo - The Karoo ice age lasted around 100 million years between 360 to 260 million years ago. It is named after glacial tills in Karoo, South Africa that scientists think were developed during this ice age.
- Quaternary - The most recent ice age is the Quaternary ice age. By scientific definition, we are currently in an interglacial stage of this ice age. It started around 2.5 million years ago and is still going.
The Earth is constantly undergoing changes. These changes can impact the global climate. Some of the changes that can influence an ice age include:
- Earth's orbit - Changes in the Earth's orbit (called Milankovitch cycles) can cause the Earth to be closer to the Sun (warmer) or further from the sun (colder). Ice ages can occur when we are further from the Sun.
- Sun - The amount of energy output by the Sun also changes. Low cycles of energy output can help in producing an ice age.
- Atmosphere - Low levels of greenhouse gases such as carbon dioxide can cause the Earth to cool leading to an ice age.
- Ocean currents - Ocean currents can have a great impact on the Earth's climate. Changes in currents can cause ice sheets to build up.
- Volcanoes - Volcanic activity can introduce huge amounts of carbon dioxide into the atmosphere. The lack of volcanoes can cause an ice age. Increased volcanic activity can put an end to an ice age as well.
- The current interglacial period that the Earth is in is called the Holocene period.
- Most of Canada was covered with ice just 20,000 years ago.
- An ice age can occur if the global temperature drops just a few degrees for a long period of time.
- Ice and snow can reflect the Sun's rays and energy, further lowering the temperature and increasing the length of an ice age.
- Mammals from the last ice age that are now extinct include the wooly mammoth and the saber-toothed cat.
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