Earthcache⛏️: Anthropogene Binnendünen auf dem Hümmling

Dunes are special geomorphological forms of sand deposition (accumulations).

The sand is called an aeolian sediment (by Aiolos, the Greek god of the wind). By turbulence of the air flow at the earth's surface, the grains of sand are thrown up and transported further.

How high they come and how far they are taken depends on their grain size and wind speed. These grain sizes are referred to with increasing grain size as clay, silt, sand or gravel. The maximum grain size of sand is 0.20-0.63 mm.

There are three types of transport: the suspension ("floating"), the saltation ("jumping") and the reptation ("crawling"). Grains held in suspension by a turbulent flow of air are referred to as floating freight. Sediments that roll or slide on the ground or jump are called ground cargo.

If the factors "big wind force" and "a lot of exposed sediment" come together, large quantities of sand are set in motion, which is referred to as sand drift, which can reach as far as the sandstorm.

The resulting dunes can be explained by Helmholtz's law, which states that when two media of different density (in our case air and sand) flow past each other, a wave-shaped interface forms. This leads to the creation of a few centimeters of small ripples, which can grow ever larger under constant conditions and pile up to dunes.

The geestmoraine Hümmling, on which we are here, is characterized by glacial (Ice Age) deposits. Through several advances of the glaciers here large amounts of sand were deposited in various particle sizes and thus form the visible here geestmoraine.

In our humid (humid) climate zone, there is actually no exposed sediment, as the rapidly spreading vegetation first prevents it from blowing and after a while completely covers the sediments. In order to understand how dunes were formed here in humid Northwest Germany, we must look back on recent history:

Until the 15th century, the Hümmling was covered by dense mixed forest with high proportions of oak and beech. In the Middle Ages (about 500-1500 AD), which is also referred to as the "wood age", man began to intensively use the large forests of the Hümmling. In addition to the logging, the forest also served as pasture for livestock.

Pigs, cattle and above all sheep ate the young shoots of the new plantlets, acorns and buckecks and thus prevented the regeneration of a closed plant cover. Even fallen leaves were used by the farmers as litter for the stable and thus contributed not to the fertilization of the soil. As a result, over time a heathland area, which in turn was subjected to intensive use by "plague farming", was strengthened from a closed forest, which in turn was compounded by the significant increase in population at the beginning of the 19th century.

At the end of this development were open sandy areas, which we would be back at the beginning of the dune formation.

At the beginning of the 19th century, the reforestation of the now desert-like areas on the Hümmling began at the direction of "Lord Arenberg". These reminded at this time already strongly on the stone deserts of North Africa. So the following picture of the Hümmling could also come from Morocco or Tunisia.

At the cache coordinates you are in the valley, between two dunes.

Please answer the following questions about this cache:


1. Fair (estimate) from the Path the height of the dunes!

2. How do you assess the danger of dune formation today? Justify your answer!

3. I would be very happy about a (voluntary) photo of you and your GPS.


Please send me the answers via email via my profile.

From the Parkingground you can reach the Earthcache from two directions. It lends itself to go to a round.