Geology of the Volcanic Region Vogelsberg

The Vogelsberg - in the heart of Hesse - is the largest volcanic complex in Central Europe with an area of about 2500 km² and a diameter of about 65 km. Isolated basalt occurrences in the vicinity of the Vogelsberg indicate a significantly larger extension of the basalt cover, which even reaches as far as Frankfurt am Main.

With a height of 773 m (normal altitude zero), the Taufstein represents the highest elevation. Today the Vogelsberg forms a landscape characterised by gentle mountains and wide plains. Valleys and rivers extend from the Upper Vogelsberg in all directions.

Where is the Vogelsberg?

The Vogelsberg with parts of the Rhoen and the Knuell belongs to the East Hessian Highlands. It lies in the Hessian "Bruchschollen-Tafelland", which is characterised by tectonic faults, ditches and nests.

The Vogelsberg is bordered to the west by the Lahn Valley and Giessen Basin, to the north by the Upper Hessian Threshold and to the east by the Fliede and Fulda Valleys. In the south-east and south there is a connection to the Spessart and Rhoen via the Hessian Ridge. In the southwest the valleys open to the Wetterau.

A "ribbon of volcanoes"

The Vogelsberg is part of a whole ribbon of volcanic centres (see illustration) that extend from the east (e.g. Eger dig) to the west (e.g. Eifel). These areas were active at different times during the geological period of the Cenozoic.

The special feature of the Vogelsberg volcanism is its diversity: activity in several phases with intermittent pauses, different eruption sites and types, and different melts. In addition, the Vogelsberg is strongly sunken in the central area, which explains its relatively flat appearance.


The inner structure of the Vogelsberg

The Vogelsberg – not only basalt!

The inner structure of the Vogelsberg consists essentially of a succession of rock units, which above all influence the groundwater and leachate of the region.

Basalt and tuff

Basalt and tuff (solidified volcanic ash) build up the Vogelsberg in alternating layers. In 2007, a 300-metre-deep borehole in Sichenhausen-Eschwald provided important insights into this process. The fissured basalt ensures good groundwater transport. The tuff layers are poor aquifers, so that the water "jams" here.

The alternation of rock layers with varying degrees of permeability leads to a groundwater storey structure: 1) the upper forest zone, 2) the floating groundwater storey zone and 3) the continuous groundwater saturation zone.

Infiltrating water meets rock layers that allow infiltration into subsoil layers (aquifers), delay infiltration (aquitards) or completely dam the water (aquifuge).

Während die Basis des Vogelsbergs komplett mit Grundwasser gesättigt ist und eines der größten Trinkwasserreservoire Hessens darstellt, sorgen die schwebenden Grundwasser-Stockwerke für viele Quellen rund um den Vogelsberg, die seinen Wasserreichtum charakterisieren. Darum dient der Vogelsberg seit etwa 150 Jahren der überregionalen Wasserversorgung, vor allem des Rhein-Main Gebietes, welcher der Hauptabnehmer des Wassers aus dem Vogelsberg ist. 

While the base of the Vogelsberg is completely saturated with groundwater and is one of the largest drinking water reservoirs in Hesse, the floating groundwater levels provide many springs around the Vogelsberg, which characterize its abundance of water. For this reason, the Vogelsberg has been used  as a supra-regional water supplier for about 150 years, mainly to the Rhine-Main area, which is the main consumer of the water from the Vogelsberg.


Research report on the Upper Vogelsberg

On the trail of secrets of the largest volcanic area in Central Europe. An interdisciplinary geoscientific research project in the Upper Vogelsberg (Source: Kracht, M. & Nesbor, H.-D. (2008)). Hessian State Agency for Nature Conservation, Environment and Geology. Wiesbaden.)


Literature

  • Ehrenberg, K.-H. & Hickethier, H. (1985). Die Basaltbasis im Vogelsberg. Schollenbau und Hinweise zur Entwicklung der vulkanischen Abfolge. Geol. Jb. Hessen (113), 97–135.
  • Francis P. & Oppenheimer, C. (2004). Volcanoes. Oxford University Press. New York.
  • Leßmann, B., Scharpff, H.-J., Wedel, A., Wiegand, K. (2000). Grundwasser im Vogelsberg. Hessisches Ministerium für Naturschutz, Umwelt, Landwirtschaft und Forsten; Hessisches Landesamt für Naturschutz, Umwelt und Geologie (Hrsgg.). Wiesbaden.
  • Leßmann, B., Wiegand, K. und Scharpff, H.-J. (2001). Die Hydrogeologie des vulkanischen Vogelsberges. Geologische Abhandlungen Hessen, Bd. 108, Wiesbaden.
  • Nesbor, H.-D. (2014). Der Vogelsberg – Vulkanologische und petrologische Entwicklung eines großen miozänen Intraplatten-Vulkangebietes in Mitteleuropa. In H.-G. Röhling (Hrsg.), GeoFrankfurt 2014 Dynamik des Systems Erde / Earth System Dynamics. Exkursionsführer und Veröffentlichungen der Deutschen Gesellschaft für Geowissenschaften. (Vol. 252). S. 22–39. Hannover.
  • Reischmann, T. & Schraft, A. (2009). Der Vogelsberg: Geotope im größten Vulkangebiet Mitteleuropas. Hessisches Landesamt für Naturschutz, Umwelt und Geologie. Wiesbaden.
  • Röhr, C. (2007). Der Oberrheingraben. http://oberrheingraben.de/index.htm. Zugriff: 28.05.2019, 11:41 Uhr MEZ.