SEA LEVEL VARIATIONS OVER GEOLOGIC TIME

2.7 to 2.1 billion years ago. Additionally, a long period of glaciation occurred shortly before the Rrst fossils of multicellular organisms, from about 1 bil-lion to 540 million years ago. Some scientists now believe that during this glaciation, the entire Earth froze over, generating a ‘snowball earth’. Such con- ................
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