Our Earth is a dynamic planet, changing on temporal scales ranging from millions of years required to complete a solid Earth cycle, or to form mountain ranges, to the few seconds required for a devastating earthquake or explosive volcanic eruptions. The Cretaceous was a period of great unrest in geologic history. It included a series of extraordinary global geological events—a significant increase of marine water temperature and the deposition of black shales; oceanic anoxia events (OAEs); biotic turnovers and mass extinctions; and the formation of many mountain ranges (California's Sierra Nevada and the Rockies in the western United States, the Andes in South America, and the Alps). Sea level rose during the mid-Cretaceous, covering about a third of the land area. Sea level was up to 250 m higher than at present.

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