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
Hampton-on-Sea dropped at Long Rock by an alternate normal east-west flow tide. When there are exceptional conditions on top of these tidal streams, for example a low pressure system causing higher water level coinciding with strong north-westerly winds, coastal flooding can occur. Hampton Brook, now Westbrook, reached the sea through a stone culvert but seaweed often blocked it, making it overflow and become stagnant. The land between the houses and the often-foetid Hampton Brook was low-lying enough to be subject to flood during a combination of spring tide, prolonged rainfall and onshore wind. Either the digging or the filling-in of the