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New York SuperGraphic

The Ice Age

The Ice Age

"Ice ages" were times when the Earth's surface was blanketed by ice sheets, or continental glaciers. Ice ages have occurred many times in Earth history, as long ago as 800 million years. They have alternated with warmer intervals in which there was probably little or no ice anywhere on Earth, even at the poles. During ice age times, glaciers expand and contract every hundred thousand years or so. This is caused by variations in the amount of sunlight reaching the Earth. Times of expanded ice are called "glacials;" times of contracted ice are called "interglacials." The most recent "ice age" began in the northern hemisphere between 2 and 3 million years ago. The most recent glacial interval ended around 20,000 years ago. Today, we are in an interglacial period. The Hyde Park mastodon thus lived during a time of warming climates.

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