A bit of geology of Holland

During the last ice age most of the North Sea was dry. When the water returned wind and waves formed a stretch of dunes in the area of the Rhine delta. The water level gradually rose further and the area behind the dunes became flooded. The area filled with fresh water from the Rhine, and a swamp was formed. Smaller rivers in this swamp carried excess water to the Rhine or other rivers. Along these rivers the banks were clayish, firmer and somewhat higher than the swamp itself. When the first human beings migrated into the area they settled on the banks. They lived on fishing and hunting.
These people came from the dune area which was inhabited already long before. The outer part of the dunes facing the sea was not attractive because of the harsh conditions. The inner part was covered with trees; there was a large forest from which Holland derives its name (Hout-land meaning Wood-land). This still is a sought-after region where richer people have their houses and where rich estates are found.

During extreme conditions the swamp was flooded from the sea; in order to keep their feet dry the houses were built on artificial mounds consisting of ground and the people′s rubbish. The photograph shows a farm on the river Alblas; it lies about 1 m above the surrounding terrain.
The frequency of flooding varied due to changes of climate which occurred on the time scale of many centuries. In adverse climatic conditions people had to give up their settlements on the river banks. Whether they returned to dryer land or perished is unknown. In the 11th century and before the river banks had become inhabited again and people had started farming on the swamp. When the flooding frequency increased in the 12th century their living conditions worsened. This time they were better organized and they took more drastic measures to defend themselves. They started surrounding their living area with dikes.

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  ©: Nico Booij (2012)