Past sea level has varied by somewhat more than a hundred metres. This is primarily due to the growth and decay of ice sheets (mostly in the northern hemisphere) with water evaporated from the sea. The Mediterranean Basin's gradual growth as the Neotethys basin, begun in the Jurassic, did not suddenly affect ocean levels. While the Mediterranean was forming during the past 100 million years, the average ocean level was generally 200 metres above current levels. However, the largest known example of marine flooding was when the Atlantic breached the Strait of Gibraltar at the end of the Messinian Salinity Crisis about 5.2
Sea level rise A rapid collapse of West Antarctic Ice Sheet could raise sea level by at an unknown rate. The Thwaites and Pine Island glaciers have been identified to be potentially prone to these processes, since both glaciers bedrock topography gets deeper farther inland, exposing them to more warm water intrusion at the grounding line, and with the continued melt, retreat, eventually raising global sea levels. Most ice on Greenland is part of the Greenland ice sheet which rises to an average of . The rest of the ice on Greenland is part of isolated glaciers and ice caps. The sources contributing