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
Mastogloia Sea a new outlet at the Great Belt. The Ancylus Lake reached the level of the sea ca. 8500 years ago, marking the beginning of the Mastogloia Sea (Björck 1995, Donner 1995). At this time the global sea level was rising rapidly as the melting of the last remnants of the great ice age ice sheets still continued (Fleming "et al." 1998). As a result, some amounts of salt water started to penetrate into the Baltic basin through the Danish straits, mixing into the vast freshwater body. This resulted in slightly brackish conditions in the Baltic. The Mastogloia Sea bears the