Eridanos (geology)

By about 12 million years ago in the Miocene, the Eridanos had reached the area currently occupied by the North Sea, where sediments carried by the river built an immense delta.

[4] The geological Eridanos was most important during the Baventian Stage about two million years ago in the late early Pleistocene, when it was about 2,700 kilometres (1,700 mi) long, a little shorter than the modern Danube.

It began in Lapland, and then flowed through the area of the modern-day Gulf of Bothnia and Baltic Sea to western Europe, where it had an immense delta, which, it is reckoned, was comparable in size to that of the current-day Amazon River.

Eridanos deposits in the Netherlands dating from the late Early Pleistocene Menapian glacial stage show the presence of Scandinavian erratic boulders ("Hattem Layers").

Eridanos sediments in the Netherlands and the neighbouring North Sea can be recognized by a high content of transparent blue-grey, lightgrey, and colorless quartz in the sand, as well as in the gravel fractions.