Kiechlinsbergen and Königschaffhausen Ihringen with Wasenweiler Riegel am Kaiserstuhl Sasbach with Jechtingen and Leiselheim Vogtsburg with Achkarren, Bickensohl, Bischoffingen, Burkheim, Oberbergen, Oberrotweil and Schelingen Wyhl Geology The formation of the Kaiserstuhl volcano during the Tertiary was the climax and at the same time the end of volcanic activity in the Upper Rhine Valley Rift. Volcanism started as early as the Cretaceous Period. Volcanic landforms include heavily eroded volcanic vents. The Kaiserstuhl is the only larger volcano from this period in the rift valley. Geologically the Kaiserstuhl can be divided into two parts: the sedimentary and volcanic part. Due to these peculiarities the Kaiserstuhl has been labeled one of the most important national geotopes. Sedimentary base The horizontal sedimentary layers forming the eastern third of the Kaiserstuhl date back to the Jurassic and the Tertiary long before the volcanic activity. Important stratigraphic outcrops include the Hauptrogenstein (local oolite) which is found mainly near the village of Riegel and the Pechelbronner Schichten (local Tertiary layers in the South German Scarplands) near Bötzingen. During the formation of the Upper Rhine Plain this part of the Kaiserstuhl sloped less in respect to its surrounding area – and thus appears as a so-called horst. In terms of its geological structure and the sequence of its escarpments, the Kaiserstuhl is comparable to the nearby Tuniberg, Nimberg and also to the Schönberg, which is situated south of the city of Freiburg. Volcanic activity Petrologically the volcanic Kaiserstuhl is an alkali-carbonate rock formation. The volcanic rocks making up a large part of the central and western Kaiserstuhl were the result of numerous volcanic eruptions during the Miocene, about 19 to 16 million years ago. They cover parts of the sedimentary base of the eastern Kaiserstuhl, which is why in some places changes in the base’s mineralogical composition occurred. The driving force behind this process of contact metamorphism was an increase in temperature. Due to the alternate eruption of tephra and lava flows from several vents a complex stratovolcano came into existence. Some of the rising magma solidified as volcanic intrusions below the surface – and today forms the central part of the Kaiserstuhl. Laterally rising phonolite magma also intruded into the sedimentary base of the Eastern Kaiserstuhl. Several hundred metres of the original volcano have been eroded. Volcanic rocks The entire volcanic Kaiserstuhl consists of rock types that contain feldspathoid minerals and olivine and are undersaturated with SiO2.