Editing Zuiderzee (section)

=== Almere ===
The [[Marsdiep]] was once a river (''fluvium Maresdeop'') which may have been a [[distributary]] of the [[Vlie]]. During the early [[Middle Ages]] this began to change as [[Floods in the Netherlands|rising sea levels and storms]] started to eat away at the coastal areas which consisted mainly of peatlands. In this period the inlet was referred to as the [[Almere (lake)|Almere]], indicating it was still more of a lake, but the mouth and size of the inlet were much widened in the 12th century and especially after a disastrous flood in 1282<ref>{{cite book |url=http://www.duizendjaarweer.nl/duizend-jaar-weer/ |last=Buisman |first=Jan |date=1995 |title=Duizend jaar weer, wind en water in de Lage Landen |publisher=Van Wijnen |location=Franeker, the Netherlands |ISBN=978-9-05194-075-6 |language=nl |access-date=23 February 2015 |archive-date=9 February 2021 |archive-url=https://web.archive.org/web/20210209134825/https://www.duizendjaarweer.nl/duizend-jaar-weer/ |url-status=live }}</ref> broke through the barrier dunes near [[Texel]]. The disaster marked the rise of [[Amsterdam]] on the southwestern end of the bay, since the seagoing traffic of the [[Baltic Sea|Baltic]] trade could now visit.{{Citation needed|date=July 2024}}

Lake Almere is mentioned among others in a life of saints written by Anglo-Saxon Bishop [[Saint Boniface]] in 753, and a deed of gift from the town of [[Urk]].{{citation needed|date=July 2020}} Its etymology may be [[Eel|eels]], in Dutch ''aal'' or ''ael'', so: ''ael mere'' = "eel lake"{{citation needed|date=July 2020}} Presumably, the water of Lake Almere at that time was fresh water or slightly [[brackish]].{{citation needed|date=July 2020}} The name of the new town of [[Almere]] in [[Flevoland]] was given in 1984 in memory of this body of water.{{citation needed|date=July 2024}}

A number of occurrences during the Middle Ages led to the transformation of the lake to an inland sea that would be called the Zuiderzee, which are:{{citation needed|date=July 2024}}

* [[Sea level rise|rising sea levels]] due to global warming known as the [[Medieval Warm Period]].
* excavation of peat by the [[Frisians]] in West Friesland near the [[Vlie]], a river that connected lake Almere to the [[North Sea]].
* floods such as the [[All Saints' Flood (1170)]] and [[St. Lucia's flood]] 1287.
Especially during the 13th century, particularly in 1219 and 1282, high tides and storms eroded the western banks of the Vlie and submerged large areas of land. The land between Stavoren, Texel, and Medemblik was washed away around 1170. The waterway between Stavoren and Enkhuizen, however, did not appear until around 1400. The erosion was stopped to the south and east by the high sandy shores of [[Gooi]], [[Veluwe]], [[Voorst]], and [[Gaasterland|Gasterland]] in the provinces of [[Utrecht (province)|Utrecht]], [[Gelderland]], [[Overysel]], and [[Friesland]] respectively.<ref name="EB1911"/>