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
Eustatic sea level Eustatic sea level The eustatic sea level is the distance from the center of the earth to the sea surface. An increase of the eustatic sea level can be generated by decreasing glaciation, slower spreading rates of the mid-ocean ridges or fewer mid-oceanic ridges. Conversely increasing glaciation, faster spreading rates or more mid-ocean ridges lead to a fall of the eustatic sea level. Changes in the eustatic sea level lead to changes in accommodation and therefore affect the deposition of sediments in marine environments. Eustatic (global) sea level refers to the sea level change of the volume of Earth’s oceans.