THE EARTH is 4.6 billion years old, and about 2.5 million years ago it entered a new stage, the Quaternary. This period has been marked by great ice ages alternating with warmer inter-glacial epochs...
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THE EARTH is 4.6 billion years old, and about 2.5 million years ago it entered a new stage, the Quaternary. This period has been marked by great ice ages alternating with warmer inter-glacial epochs...