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 studying the state of frozen water and the ocean on our planet factor in ongoing deformations of the solid Earth, in particular due to landmasses still rising from past ice masses retreating. Additionally, Earth gravitation and rotation have to be accounted for. These factors are dependent on the different layers which make up the Earth (lithosphere, asthenosphere), and the order in which land-based ice melts. Because the involved processes, which are collectively known as the "Sea-level equation", change very slowly, on time scales of thousands of years, they are considered to be constant. Since the 1992 launch of TOPEX/Poseidon, altimetric