taken from the on-site information board:
The Kampen boulder from the Roten Kliff
Data on the boulder:
Type of rock: biotite gneiss
Size: over 3.5m high
Weight: about 20 t (400 quintals)
Location: next to a groyne on the main beach
Salvage: March 2005
The boulder from the Roten Kliff is a stone that weighs around 20 t and is more than a billion years old. It is a gneiss from the Scandinavian mountains.
The stone used to be a granite with unregulated minerals. In the depths of the earth, at high temperatures and great pressure, the granite was transformed into gneiss. The individual minerals are arranged parallel to one another.
In the boulder there are inclusions (lenses) of dark foreign rock that penetrated during the transformation into the then plastic granite and were also adjusted. During the Ice Age over 200,000 years ago, part of a gneiss complex in Scandinavia broke loose from the mighty glacier and was transported hundreds of kilometers to Sylt in the ice stream. This stone, rounded off by the transport, is now called a boulder and could thus be recovered from the Kampen beach.