You know what kind of weather to expect at each time of year, at least for the place where you live. That's because you're familiar with the climate—the typical range of weather for a region. Did you know that Earth's climate hasn't always stayed the same? Every once in a long while, the Earth goes through a period of especially cold weather called an ice age.
WHAT HAPPENS DURING AN ICE AGE?
Today, ice covers Earth's North and South poles. These ice caps are called polar glaciers. During an ice age, the polar glaciers grow larger. At the height of an ice age, glaciers may cover as much as a third of the Earth. Canada, the northern United States, northern Europe, and northern Russia all get covered by ice. This ice can be more than a mile [1.6 kilometers] thick.
Much of the world’s water gets frozen to make these glaciers. This water comes from the oceans, and sea level drops as a result. Places that had been under water become dry land. Many plants and animals adapt to these changes. Those that do not adapt die out.
During the last ice age, animals with warm shaggy coats flourished. For example, the woolly mammoth, a large elephant-like animal, roamed icy areas of Earth. The mammoths probably used their huge tusks to scrape away the snow in search of plants to eat. Their thick woolly coats protected them from the cold.
HOW LONG DOES AN ICE AGE LAST?
An ice age can last for tens of millions of years. The warm periods between ice ages last hundreds of millions of years.
Earth can warm up somewhat for short periods during an ice age. A warm time within an ice age is called an interglacial. Several interglacials can occur during an ice age. Each one may last for 10,000 years or more.
Ice ages are not like seasons. They do not arrive on any known schedule. In fact, no one can tell when an ice age is beginning. The climate changes very slowly.