The Kaiserstuhl (, "Emperor’s Chair") is a range of hills in the state of Baden-Württemberg in southwest Germany with a maximum height of . It is of volcanic origin and located in the southwest of the state in the counties of Emmendingen and Breisgau-Hochschwarzwald. In terms of natural regions it is considered to be a part of the Upper Rhine Plain.
Name The name "Kaiserstuhl" is believed to refer to King Otto III, who held court near Sasbach on 22 December 994. From then on, the whole hill range was called the Königsstuhl – the King's Chair. In May 996, Otto III was crowned Emperor and the King's Chair eventually became the Emperor's Chair – "Kaiserstuhl". Reliable sources mention the name Kaiserstuhl only as early as 1304 and historians thus suppose that the term Kaiserstuhl was not coined until the 13th century.
Geography
Location The Kaiserstuhl is situated in South Baden, mainly in Breisgau-Hochschwarzwald county or district. However, the smaller northern part belongs to Emmendingen. Within the Upper Rhine Plain it is situated about 16 km northwest of the city of Freiburg, right next to the eastern bank of the Rhine and a short distance west of the Dreisam. It reaches up to 377 metres above the level of the Rhine downstream (179.5 m a.s.l.) from the weir close to Burkheim.
At its greatest extent, from the Michaelsberg near Riegel in the northeast, to the Fohrenberg, by Ihringen in the southwest, the Kaiserstuhl is about 15 km long. Its maximum width is about 12.5 km.
Hills The hills of the Kaiserstuhl include the following (sorted by height in metres above sea level): Totenkopf (556.6 m), 1.9 km east of Bickensohl; with the Vogtsburg 1 telecommunication tower and Neunlinden observation tower Eichelspitze (521.3 m), 2.8 km northwest of Bötzingen Katharinenberg (492.4 m), 1.3 km southeast of Amoltern Bisamberg (469.0 m), 1.2 km south of Amoltern Staffelberg (446.0 m), 1.5 km northwest of Schelingen Badberg (432.7 m) (protected area), 1.5 km east of Oberbergen Holzeck (431.9 m), 1.7 km northeast of Ihringen; with tower Hochbuck (374.8 m), 900 m south of Achkarren Schlossberg (352.1 m), 500 m northwest of Achkarren; with Höhingen Castle ruins Böselsberg (340.1 m), 500 m northwest of Wasenweiler Büchsenberg (283.7 m), 1.3 km west of Achkarren
Towns and villages Towns and villages in and around the Kaiserstuhl (in alphabetical order) are: Bahlingen Bötzingen Breisach Eichstetten Endingen with Amoltern, 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. Most igneous rocks at the surface are leucite-tephrites, with subordinate phonolites, limburgites, and olivine-nephelinites (at the Limberg Mountain near Sasbach), the last of which is rich in xenoliths from the Earth's mantle. Carbonatite ignimbrite and lapilli are local peculiarities; they can be found in places in the western part of the Kaiserstuhl (Henkenberg near Burkheim, Kirchberg near Oberrotweil).
The subvolcanic and intrusive rocks of the central Kaiserstuhl are plutonic equivalents of the erupted material (essexite, carbonatite and coarse-granular phonolite). Several local terms which do not carry official status with the International Union of Geological Sciences have been used for different varieties of the intrusive rocks. Of major scientific interest is the consolidated carbonatite near Altvogtsburg und Schelingen. It is a quite rare volcanic rock, which crystallized from a carbonate magmatic melt rather than a silicate one. Given its unusual composition for an igneous rock, the magmatic nature of the carbonatite was not proposed for a long time and remained doubtful subsequently. An alternative interpretation was that it was a metamorphically altered sedimentary rock, examples of which can be found nearby. Only in the 1950s and 1960s did research prove that it was a carbonatite; one of the clues was identification of the eruptive carbonatites found in the western part of the Kaiserstuhl. The carbonatite contains the niobium rich pyrochlore; attempts to mine the carbonatite rock for niobium were carried out in the middle of the 20th century, but the amount turned out to be too small to be economical.
Minerals For a long time the Kaiserstuhl has been known for rare minerals. Examples include the quarries at the Limberg (zeolites), Badberg (carbonatites), Orberg and Fohberg. Well-crystallized minerals can be found predominantly in clefts or cavities in the volcanic rock.
Loess
The Kaiserstuhl is today largely covered by a Quaternary loess layer, a loosely cemented sediment. It is derived from other rocks through erosion and is then transported by the wind. The loess at the Kaiserstuhl – as in all the peripheral areas of the Upper Rhine Valley – was formed during the last Ice Age. Large parts were bare of vegetation and so loess was winnowed out from the Rhine sediments. It was then deposited in the periglacial area (i.e. ice-free, but surrounded by glaciers) at the Kaiserstuhl. The major process active here was frost weathering resulting in crushed rocks. The wind blew strongly, as there was no vegetation that could have moderated it – entraining the lightest material and depositing it at obstacles like the Kaiserstuhl. Deposition took place northeast of the Kaiserstuhl, as the winds blew from the southwest.
The higher the place of sedimentation, the thinner the layer of the sedimented material is. At the Kaiserstuhl the thickness of the loess layer varies between 10 and 40 metres. There are, however, also areas in the southwest where no loess has been deposited. The Northern Limestone Alps are considered the main source of the Kaiserstuhl loess. A rust-coloured band occurs at irregular intervals. It developed as a new material and did not arrive regularly but in phases of different intensities. In a phase of weak sedimentation the material on top weathered – and the calcium carbonate was washed out. It then precipitated further down and formed a particular type of soil horizon, which contains concretions of calcium carbonate.
The Kaiserstuhl loess soils are used for intensive farming, as they offer good aeration, high water storage capacities and good mechanical qualities. Besides, as a result of farming deep narrow ravine-like paths developed.
As the loess developed over time it is, furthermore, significant for flood control. Sponge-like, it absorbs and then gently releases rainfall. This quality is however lost when bulldozers, employed to construct large terraces for viticulture, compress the loess.
Climate
General
The Kaiserstuhl is one of the warmest regions in Germany. The climate in the area is a continentalized form of the mediterranean climate (Köppen climate classification: Csa). This is unique at 48° north latitude. Its location in the southwestern corner of Germany and the protection of the mountains give it a warm microclimate, which is influenced mostly by air from the western Mediterranean Sea blowing through the Burgundian Gate. Atlantic air masses can raise the temperatures especially in winter as well, while the surrounding mountains are able to hold most of the precipitation away from Kaiserstuhl. This is why the Region features nearly 2,100 sunshine hours and only around 500 milliliters of precipitation a year, while the nearby Black Forest has levels up to 2,000 milliliters a year.
Winters are short and mild, although light night frost can occur especially in January. Days are mostly cool to mild with changeable weather and, in the recent years, with a tendency to more precipitation during this period. Snow is very rare and concentrates mostly on the higher regions if it occurs.
Spring starts generally in February and is characterized by the almond flowering trees, which are typical for the region. The time between February and May counts many days exceeding and therefore counts as one of the warmest and sunniest spring climates in the country.
Summers (June to September) can be very hot and with temperatures often exceeding the during midsummer. Because of its loess covered volcanic soils and the climatic situation, it is an internationally renowned wine-producing region. In recent decades, there has been a tendency to very low precipitation during the summer months.
Autumn starts warm to still hot in September and cools down to around by November on average. As the rest of the year, the southern location and direct Mediterranean influence can make autumns warm and pleasant with temperatures up to even in the second half of October, which is very rare in other parts of Germany.
Besides the wine, the mild climate enables the wild cultivation of other sensitive fruits and vegetables like kaki, olive trees, fig trees, and banana plants. The region is also known for its wild growing cactus on old lava stones in the slopes of the Kaiserstuhl.
Flora and fauna