What event in 1170 may have caused the creation of 5,000 km2 large shallow bay of the North Sea in the northwest of the Netherlands?
All Saints' Flood (1170) The All Saints' Flood of 1170 (Allerheiligenvloed) was a catastrophic flood in the Netherlands that took place in 1170. Large parts of the Northern Netherlands, and Holland territories were overflowed. This is the flood that created the Zuiderzee. "Lake Flevo" was once a fresh water lake, but after this flood a sea channel opened a connection from the North Sea into the lake through Creil Woods, and turned the lake into the salt-water sea known as the Zuiderzee. The Creiler Forest vanished forever under the waves.
Naval war on Lake Constance The naval war on Lake Constance (German: "Seekrieg auf dem Bodensee" ) was a series of conflicts that took place on Lake Constance, beginning in 1632, in the context of the Thirty Years' War (1618 to 1648). At that time various powers ruled different parts of the shoreline: in the north and east was Roman Catholic, Habsburg Anterior Austria; in the northwest and west the troops of the Protestant Duchy of Württemberg with their allies from Kingdom of Sweden and Kingdom of France. These various powers sought, for strategic reasons, to exercise their hegemony over the area of Lake Constance. Only the partly Catholic and partly Protestant southern shore which belonged to the Old Swiss Confederacy maintained an uneasy neutrality due to their divided loyalties.