What Made the Ice Ages Happen?

There are many theories, or ideas, about what made the Ice Ages happen. Scientists think that the whole Earth's climate, or weather, became about 10 degrees cooler for many, many years. Winters became much longer. Summers became much shorter. Winter snows didn't melt and just kept piling up. After a time, glaciers, or slowly moving rivers of ice, formed over many parts of the Earth. Some of these glaciers were 2 miles high! There are still glaciers today. The picture above this paragraph shows a man standing on a glacier.

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