Unkelstein

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Unkelsteine ​​in the Rhine. Hogenberg: Attack on Unkel 1583.

The Unkelstein is a basal reef at Rhine kilometer 636.6 at the height of Unkel and Oberwinter . The shoal was clearly visible until the 19th century, even at higher water levels, and was a long-feared obstacle for shipping. The striking rock outcrops in the Rhineland gave its name to the basalt , which was called Unkelstein here .

geology

The Unkelsteine ​​were among the most striking basalt outcrops in the Westerwald and Neuwied Basin, which are rich in basalt deposits . The "small and large Unkelsteine", made up of basalt columns and reaching right into the middle of the Rhine, belong geologically to those deposits that were mined in the immediate vicinity on the left bank of the Rhine as early as Roman times. Basalt from this deposit was widely used in the construction of cities, castles, churches and fortresses, in paving streets and in fortifying dams in Holland.

history

Rhine map from 1855 with Unkelstein opposite Unkel

Until the 19th century, the Unkelsteine ​​belonged to the dangerous shoals of the Rhine that were feared by boatmen . In the historical sources there are several references to efforts to remove the stones and defuse the shoals. For example, during the occupation of the Rhineland , the French government had cliffs destroyed to make shipping easier. The Oberwinterer resisted the demolition work because the Unkelstein shields the place from the ice.

Today a green buoy at the edge of the fairway indicates the critical shoal, which still causes unpredictable currents and eddies and which is occasionally marked by foam-crowned waves even when the Rhine is calmly flowing.

The Unkelsteine ​​in the history of science

The Unkelsteine ​​near Oberwinter met with great interest from the emerging earth sciences in the 19th century. As a student, Alexander von Humboldt went on an excursion from Bonn in 1789 to check on the spot descriptions by two contemporary naturalists - Jean André de Luc and Cosimo Alessandro Collini - who had come to different theories regarding the Unkeler basalt outcrops. It was about the dispute between Neptunists and volcanists about the formation of the earth's crust.

Humboldt himself, who in his early years initially leaned towards Neptunism , came to the conclusion after this trip that basalts were not of volcanic origin, but formed a gradually hardening desiccation of a marine deposit .

Once again, Humboldt and the naturalist Georg Forster visited the place, who, as he notes in his travel notes, could not have imagined that basalt could have arisen from maritime deposits, but its formation in the burning gullies that we call volcanoes, seems completely contradicting and impossible.

Individual evidence

  1. ^ Rheinischer Antiquarius, Section 3, Vol. 9, p. 382 f.
  2. ^ Rheinischer Antiquarius, Section 3, Vol. 9, p. 381.
  3. ^ Humboldt: Mineralogical observations on some basalts on the Rhine. With preliminary, absent-minded remarks on the basalt of the ancient and modern writers. Braunschweig 1790. dig
  4. ↑ quoted from Kremer.

literature

Web links

Coordinates: 50 ° 35 ′ 59 ″  N , 7 ° 12 ′ 40 ″  E