North Hessian volcanic area
The volcanic relics and phenomena in the area of Hesse and Lower Saxony that can be found in the Knüllgebirge , in the Kellerwald , in the Gudensberger Kuppenschwelle , in the Habichtswälder Bergland , in the Reinhardswald , in the Kaufunger Forest and on the Hohen Meißner are summarized as the North Hessian volcanic area or volcanism of the Hessian Depression . In total, more than 2000 separate volcanic relics can be found in this area, including Germany's northernmost volcano.
Appearances in the terrain
Most of the volcanoes in the regions mentioned are eroded chimneys , in which no relics of near-surface volcanic formations (craters, eruption cones, etc.) are recognizable. Only in the Habichtswald area are volcanic tuff rocks more widespread. In addition, however, there are also larger sub-volcanic formations that were exposed by the erosion of the rock cover originally lying above. The frequency of such formations is explained by the fact that at the time of volcanic activity in this area relatively soft sedimentary rocks were to be found widespread, which had little resistance to oppose a lateral, layer-parallel intrusion of magma . At the same time, these intrusions cannot have taken place at too great a depth, because the rocks do not differ significantly from volcanic rocks formed by effusion.
Age of volcanism
The volcanic activity in the Hessian Depression extended over a period of 25 to 5 million years before our time, with a focus of the activity in the Upper Miocene 14 to 13 million years ago.
Significant individual occurrences
High Meissner
The Hohe Meißner is a classic example of the sub-volcanic formation of a basalt body. Its basalts seem to form smaller ceilings that were initially considered relics of a superficial effusion of lava, but are now interpreted as exposed intrusive bodies.
Bühl near Kassel
The basalt chimney from Bühl (Weimar) is famous as a place where naturally formed, metallic iron was found in basalt. The magma broke through a brown coal seam there, which resulted in locally reducing conditions and the magnetite present in the magma was reduced to iron on the spot.
Blue top near Eschwege
At the Blauer Kuppe , too , the rising magma has interacted with the surrounding rock - here sandstones of the red sandstone - and transformed the sandstone to a large extent into Buchit through contact metamorphosis . After the eruption, pneumatolysis also formed a characteristic mineral community in this chimney .
Ultrabasic volcanic rocks near Hofgeismar and Fritzlar
In the area of Hofgeismar and in space Fritzlar are several places foiditische volcanics minded that the rare mineral Melilith lead.
literature
- Hofbauer, Gottfried: Volcanoes in Germany. Scientific Book Society, Darmstadt 2016, pp. 158–167.
- Wedepohl, KH: The tertiary basaltic volcanism of the Hessian Depression north of the Vogelsberg. In: The opening. Special volume 28, Heidelberg 1978, pp. 156-167.
- Hentschel, Hans: The basalt of Meißner. In: The opening. Special volume 28, Heidelberg 1978, pp. 208-228.
- Koritnig, Siegmund: The "Blue Dome" near Eschwege. In: The opening. Special volume 28, Heidelberg 1978, pp. 237-247.
Individual evidence
- ↑ a b Hofbauer, p. 158
- ^ A b Wilke, Hans-Jürgen: Mineralfundstellen Hessen, 2nd edition, Christian Weise Verlag, Munich 1981, p. 31
- ↑ Wedepohl, pp. 162–163
- ↑ Ludwig Lohmann: A contribution to the petrography of melilite-leading olivine nephelinites from the Fritzlar-Naumburg area (Northern Hesse) . In: Contributions to mineralogy and petrography . tape 9 , 1964, pp. 533-584 .