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Ice Age for Kids - When was the last ice age - What caused the ice age

What is an ice age?

Have you ever tried to make a snowball?
Snow is soft and fluffy when it falls from the sky, but when you press it into a ball, it can become quite hard. If you press it very tightly, it turns into a lump of ice.
It is so cold at the North and South poles, that the snow there never has a chance to melt. As more snow falls, it presses down into tightly packed layers which then turn to ice.
Some areas of the earth are covered by huge sheets of ice and snow all year round.
Around the North Pole there is no land, but an ice sheet, also known as a continental glacier, covers the Arctic Ocean.
An ice sheet also covers most of Greenland and some northern parts of Canada and Europe.
The largest ice sheet in the world lies around the South Pole. It covers about 5.1 million square miles (13.2 million square kilometers) of the huge continent called Antarctica.
This ice sheet has an average thickness of 6,600 feet (2,000 meters).
The Antarctic ice contains about three-quarters of all the earth's fresh water.

For hundreds of years, many layers of ice have been forming in the Arctic and in Antarctica.
Scientists can now dig down into the ice to find traces of the past.
In Antarctica they have already found fossils of plant life, coal and other minerals.
Ice taken from deep down under the surface of Greenland shows that the air has been polluted with lead for hundreds of years.
Samples of ice also prove that lead pollution has become much worse during the past 100 years.
Scientists believe that most of this pollution is caused by the lead in gasoline.
The huge ice sheets around the North and South poles were once even bigger than they are now!
In the past, there were long periods of time when ice actually covered large areas of North America and northern Europe.
These periods of time are called ice ages.

When was the last Ice Age?

The most recent ice age began about 2 million years ago. The map shows which areas of
and is known as the Pleistocene Ice Age.

During each ice the world were covered with ice age, the ice advances and retreats several times. during the Pleistocene Ice Age.
In past ice ages, each advance of ice, or glaciation, lasted from 40,000 to 60,000 years.
In between glaciations there were interglacial periods of about 40,000 years, when the ice melted and retreated.

What causes Ice Ages?

Most scientists believe that ice ages are caused by a regular change in the shape of the earth's orbit around the sun.
This change seems to happen periodically, when the surface of the planet cools and huge ice sheets form. Since the last ice retreat began less than 20,000 years ago, we are now living in an interglacial period.
Some time in the future, the ice will advance again!

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