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Why were sea levels much higher during the Cretaceous Period?
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Cretaceous Period
Distribution of landmasses, mountainous regions, shallow seas, and deep ocean basins during the late Cretaceous Period. Included in the paleogeographic reconstruction are the locations of the interval's subduction zones.
During the Cretaceous Period, sea levels were significantly higher than they are today, reaching levels approximately 100 to 250 metres (330 to 820 feet) above current marks.
This phenomenon is primarily attributed to the displacement of water within ocean basins caused by the enlargement of midoceanic ridges. As these ridges expanded, they occupied more volume on the ocean floor, effectively forcing the water level to rise and inundate continental margins, which created extensive epicontinental seas across the globe.1