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 This is not a physical level but instead represents the sea level if all of the water in the oceans were contained in a single basin. Eustatic sea level is not relative to local surfaces, because relative sea level is dependent on many factors including tectonics, continental rise and subsidence, and many others. Eustatic sea level follows the ‘Bath Tub Theory’ which describes the ocean as a single bath rub. You can add or remove water and Earth’s oceans will gain or lose water globally. Differences of Eustatic sea level are caused by 3 main factors: 1. Changes in total