Marl boundary

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Memorial plaque for one of the first successfully sunk underground construction shafts in the Ruhr area north of the marl border

The marl boundary separates two areas of hard coal mining in the Ruhr area . It runs roughly in the west - south- west - east-north-east direction a few kilometers north of the Ruhr , south of it the coal mountains come to light. In the southern area, the seams can therefore be mined in open-cast mining or through simple tunnels , as the folds in air saddles, among other things, make it relatively easy to follow layers falling obliquely to the earth's surface . Because of the many smaller valleys in this area, the resulting groundwater can be drained off through tunnels , and ventilation is also not very expensive.

To the north of the marl boundary, the coal mountains are covered by an increasingly thick layer of marl . This layer is highly water-bearing and can only be penetrated by a shaft if it is carefully sealed during construction . The pit water has to be pumped out of the mine , and very large fans provide the necessary ventilation.

The marl overburden was first overcome in 1811 in the Am Busch colliery in the south of Dortmund. Other sources give the date 1834 in today's Essen district of Essen-Borbeck and 1841 at the United President colliery in today's Bochum district of Hamme for the breakthrough through the overburden made of marl . The mechanical expenditure for mining north of the marl border forced the entrepreneurs to concentrate on a few large collieries in order to keep the capital expenditure for such plants halfway profitable . The existence of the marl border has therefore decisively shaped the Ruhr area.

Even today, the marl boundary is important: to the south of it you can still expect breaks in the daylight, while further north the subsidence of the landscape is a result of mining. a. Causes mountain damage .

In order to prevent water ingress into the mine , compliance with a marl safety pillar is required by the mining authorities. 20 meters from the footwall of the marl border in seigere direction must not be dismantled.

literature

  • Fritz Heise, Fr. Herbst, Carl Hellmut Fritzsche: Mining studies . Textbook of, with special consideration of the coal mining industry. 8th and 9th completely revised edition. tape 2 . Springer-Verlag, Berlin / Göttingen / Heidelberg 1958, p. 362 .

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