Bollenberg Hill - Geology and Climate

Bollenberg Hill is a triangular relief sloping gently southeast, dominated by three peaks, the highest reaching 363 meters.

It overlooks the Ohmbach valley, offering a remarkable panorama of the surroundings. Three major faults structure the site: to the east, the Rhine fault is partially hidden by loess deposits; to the west, the Marbach fault separates it from Pfingstberg; to the north, the Ohmbach fault distinguishes it from its twin hill, Strangenberg. The western ridge, made of Grande Oolithe limestone, forms compact and dry layers favorable to the development of calcareous grasslands. This substrate was once used for lime stone extraction. The east and northeast slopes, on the other hand, are covered with vineyards and rest on marl-limestone and loess deposits, which are thicker and more fertile.

The hill's particular climate is explained by its position within the Guebwiller fault field: humid westerly winds condense on the Vosges, while the sunniest zone of the hills sees residual moisture evaporate. With an average annual rainfall of 400 to 500 mm, mainly concentrated in intense summer storms, Bollenberg is the driest limestone hill in France, a balance that limits extreme dryness thanks to these sudden precipitations.