Göfis Kettle Basin
Because of missing scientific explanations these strange holes, tubs and pits in the firm rock inspired the fantasy of humans over centuries. In earlier times the alpine inhabitants regarded these phenomea as works of witches and giants. Conveyed names such as devil mills, witch boilers, devil holes, giant pots or victim boilers are witnesses of it. It lasted for a very long time, until the strange forms were related to the glaciation of the alps with beginning of the research in the past century.
In the Ice Age Vorarlberg was nearly completely covered with enormous glaciers. The Ill glacier (Illgletscher) was formed in the valleys of the upper country and flew through the Walgau region over a rock threshold. The superior Rhine glacier (Rheingletscher) which was moving from Graubünden (Switzerland) to the Rhine Valley pushed the Ill glacier to continue to Dornbirn and into the Bregenzerwald. During the large freezing the Ill glacier filled up the exit of the Walgau region.
Kettle basins result from abrasion effects of rock fragments: Gravel, sand or silt are whirlingly moved by the meltwater at the rock bottom, which falls down vortex-like into glacier crevasses. In the stationary whirl the sediment carrying meltwater grinds deep hollow forms into the rock. Smaller rock particles carried by the water in the turbulences with speeds up to 200 kilometers per hour are hurled against the walls of the pot. Sometimes a larger rounded stone can be found at the bottom of a kettle basin. However the fine sediment freight in the meltwater is more important than this “grindstone” for the emergence of the glacier pot.
Kettle basins can be found in the forms of round tubs of several meters in diameter on the rocky valley ground, screw-like hollow forms or as lateral bulges in the cliffs. To log this Earthcache you have to answer the following questions:
1. How many years ago the glaciers in Vorarlberg melted?
2. Up to which height the exit of the Walgau was filled up during the large freezing?
3. The Ill glacier transported different kinds of rock from different catchment areas. Call the kinds of rock and the associated catchment area.
Send an email via my GC-profile and wait for log approval. After logging don’t forget to attach a photo of you and the kettle basin to your log.