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.
Cymbrian flood The Cymbrian flood (or Cimbrian flood) was a large-scale incursion of the sea in the region of the Jutland peninsula in the period 120 to 114 BC, resulting in a permanent alteration of the coastline with much land lost. This disaster killed many, and sent others living in the area south in search of new lands. It was one of a number of such conflagrations of nature in northwest Europe during the Roman period, the climate between 300 BC and about 100 AD producing frequent storms and the blowing of sand near the coast.