Der Große Pfahl bei Viechtach

The "Pfahl" is a quartz filled crack in the earth´s crust, which extends over a distance of 150km from the "Oberpfalz" in Germany to "Upper Austria". Near Viechtach in the Bavarian Forest, it appears quite impressive.
The coordinates 49° 4.826' N 12°51.925' E lead you to a parking lot directly at the Bundesstraße 8. From there you can start a short walk around the "Devil´s Wall"
How did the Pfahl arise?
The Pfahl arose from a tectonic crack. 275 millon years ago the Forward Bavarian Forest was lifted a few hundred meters over the Inner Bavarian Forest, which caused this crack in the earth´s crust. It was filled with quartz which was dissolved from the surrounding rocks by hot water. All this happened in a depth up to 6 km.
How did the Pfahl get visible?
Over many million years the softer minerals which surrounded the Pfahl were removed by erosion. Due to its harder mineral the Pfahl itself could resist the erosion much better and is visible at many places since then.
What does the Pfahl consist of?
The Pfahl predominantly consists of the white to light-grey coloured Pfahlquartz. Pfahlquarz is composed of 95-98% silicic acid (SiO2) and small amounts of kaolinite and sericite.
What was Pfahlquartz used for?
Pfahlquartz was mainly used to make road gravel. But there are also some high purity quartzes which can be used for glass making and semiconductor production (silicon).
To log this cache you have to take a picture of you and your GPSr in front of the Pfahl.