Geology

The ice ages

The current land-forms of the Veluwe originated from the Pleistocene ice ages. About 130,000 years ago, in the Saalien glacial era, a continental ice-sheet from Scandinavia advanced to the Netherlands from the north until it covered the Northern part of the country.

Glacial hills

The glacier front ended in lobes excavating depressions in the loose coarse sands, the sediments of the rivers Rhine and Maas. Laterally along the ice lobes the frozen sands were pushed up into glacial hills, known locally as lateral moraines or 'stuwwallen'. These are now the basis of the hilly zones of the Veluwe area. The highest of these, which goes up to more than 100 meters, forms a curve west of the town of Apeldoorn and extends from Hattem in the north to Arnhem in the South. A smaller one is to be found between Harderwijk and Garderen. The depression between both moraines, nowadays the Leuvenumse Beek valley, is thought to have been created by one of the lobes of the Arctic ice front. When the ice front eventually retreated back North, the valley was partially filled up with sand and gravel deposited by the melting ice water. These terraces of sand and gravel are the geological basis of the area around the village of Uddel.

Pingos

During the latest ice age (some 10,000 years ago) the arctic ice sheet did not reach the area of the current Netherlands any more. Nonetheless there were periods of permafrost, with permanently frozen ground water. During these periods pingos, which seems to be an Eskimo name, where formed. These are cone shaped mounds of soil caused by intrusions of ground ice. Apparently they form where unfrozen ground water is trapped between two frozen layers. In summer times the top layer of the soil would melt and slide off of the pingo hill. After many years of this process being repeated, the result is a ring of soil with a crater in the middle. Sometimes the crater fills with water to form a small lake. The Bleeke Meer and Uddelermeer are assumed to be examples of such pingo lakes.