In this wooden area in Bergisch Gladbach's district Nussbaum (what means nut tree in English), right in the middle of the chalk basin of Paffrath, can be found a bench of funnel shaped basins in the ground. These are dolines (from the Slovenian word Dolina = valley), a typical appearance in karst areas. Practically all forms which appear through alteration in chalk rocks can be understood as karst.
Dolines arise when the underground’s limestone is dissolving through the contact with carbonic acid. So it comes to the formation of sinkholes. When the stability of such a cave ceiling is not given any longer, this breaks in and a landslip doline accrues. If the underground is washed away slowly the word is about a solution doline. In this region the diameter of these funnels ranges between 2 and 200 meters with a depth of 2 to 300 meters. The karst sinkholes are filled with tertiary sands and particularly with loess. Loess comes through wind sedimentation which is usually built up from silt (ablated fine loan and sedimental rocks with a grain size of 0,002mm to 0,063mm) and finest sands. Mineralogical its main parts are consisting of Quartz, limy fragments and several regionally different minerals.
When a spring comes out of the karst, which can be watched frequently here in this area, (e.g. the spring of the Strunde in Herrenstrunden or the small rivulet at the Kuckelbacher Hof) so it is the speech of a karst spring. Thereby the water, which is mainly consisting of rain, floats for kilometers downhill through the porous and cavern karst rocks to return back to day on a deeper place. It is not unusual that the water presses through the surface ground and searches its way through the loess. It drips back into the ground, and finally comes out again on another place. The water which is drawning through this area can be seen as origin of the Mutzbach who drips to the underground in the South and appears again at the Paffrather Mulde. Originally the percolation lay close by today’s sheeplawns. At heavy rains the waters could ooze out again and float the area, so the rivulet was artificially bypassed.
To log this Earthcache you’ll have to perform the following tasks:
1. Go to the coordinates and look around. How many dolines can be seen in your opinion?
2. Some of the trees which are growing here are showing a remarkable habit. Think about the possible cause for that and which relation there could be in relation to the doline field.
3. Send us a mail with your answers.
You may log this Earthcache online without our permission. But if the answers stay out or if we receive senseless responds we will check this with you and -in last consequence- delete the log. A picture of the pretty region with or without yourself on it would be nice, but of course, is just optional.
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