Beneath the Ruhr lies a network of 22,160 coal seam lines

Beneath the Ruhr lies a network. The hard coal map of the Geological Survey of North Rhine-Westphalia records 22,160 seam lines, and this network tilts away to the north. In the south of the coalfield the coal lay at the surface. Beneath Recklinghausen it lies about 480 metres deeper below ground than in Witten. Our new episode shows this underground as a 3D model built from the official data. It also follows one name that chased this tilted coal for almost two hundred years, from a shaft that found no coal to the last piece ever mined in Germany.

A network at the top of the Carboniferous

The 1:10,000 map was compiled between 1949 and 1954 and was meant even then as a general overview, not a survey. It records the seams, the layers of coal themselves, where they meet the upper edge of the coal-bearing rock. Geologists call this edge the top of the Carboniferous. So the lines do not lie at ground level but below it, almost at the surface in the south and under hundreds of metres of rock in the north. Across North Rhine-Westphalia there are 22,160 lines, and 548 seams carry a name. That is why we speak of seam lines rather than 22,160 seams.

Not every line is equally certain. Of the 19,756 lines in our narrower Ruhr window, 5,512 count as confirmed, 7,165 as constructed and 7,078 as projected. The model draws the confirmed ones strongly, the constructed ones thinly and the projected ones not at all. Heights are exaggerated fifteen times, and where the map ends, the model ends too. The swamp forest and the Cretaceous sea, the historical scenes with miners and the piece of coal from 2018 are AI images, labelled in the picture. The people in them are not real people. The 3D flights, by contrast, are our own animations of the official data.

Why the coal dips to the north

The coal formed more than 300 million years ago, in the Upper Carboniferous, from swamp forests that were buried layer by layer and pressed into seams. Later the rock was folded, lifted and worn down, and that is how it got its tilt. In the Cretaceous a sea laid down marl over the northern part, up to 600 metres thick. Miners called it Emscher marl. It holds back water, and it is the main part of the overburden, the younger rock above the coal. The Geological Survey puts it briefly. Along the Ruhr the coal comes to the surface, to the north more and more cover lies on top, and the top of the Carboniferous dips gently northwards.

On the map this surface reaches up to 300 metres above sea level around Witten and Hattingen, and lies almost 600 metres below sea level near Datteln. Together with a terrain model you can work out how much rock lies above the coal. In Witten it is about 10 metres, in Essen and Bochum around 30, in Gelsenkirchen 140, in Bottrop 260, in Recklinghausen 490 and in Datteln 640 metres. That is where the 480 metres in the episode come from. These are rounded averages and a minimum figure down to the coal, and they say nothing about any single plot of land. Gentle, say the geologists. For a miner, 480 metres is not gentle.

Coal at the surface, and a shaft without coal

The story begins in the Mutten valley near Witten. As far as records go, someone first applied here in 1714 to mine coal from a seam in the Hettberg woods. Nobody needed a shaft. Miners drove an adit into the hillside, to where the seams came to the surface, and took the coal out as if from a cellar. The Nachtigall colliery that grew from this later went deep itself, and in 1876 its Hercules shaft reached 450 metres.

Further north the coal had vanished under the marl. Franz Haniel, born in 1779, was not a miner but a merchant in Ruhrort. He suspected that the coal carried on beneath the cover rock, while many mining experts of his day thought those wet, chalky layers could hardly be overcome. In 1832 Haniel had his own shaft sunk south of Borbeck, the Franz shaft. By late summer 1833 it reached about 54 metres down, and there was still no coal. The money was his, and the doubters seemed to be winning. On 27 March 1834, after 19 months of work, Haniel reached a seam through a crosscut. Two days later the mining authority came to inspect it. The coal carried on. It just lay deeper.

Following the coal to the Lippe

Haniel kept moving north. In 1847 he had the first shaft of the Zollverein colliery sunk in the north of Essen. At first the coal was worked at a depth of 170 metres, and by 1908 at 600 metres. The collieries followed the coal, reaching the Emscher by the mid 19th century and crossing the Lippe around 1900, each step north leading further down. In the model you see this as needles. Each one stands for one of 1,199 shafts and adits from open data and runs from the ground to the top of the Carboniferous. It shows the cover rock above the coal, not the length of the shaft, which we mostly do not know. In the south the needles are short, and at 305 shafts the coal lies less than 15 metres down. In the north they grow long, reaching almost 900 metres at the Westfalen colliery in Ahlen, on the edge of the map.

Marl shows how hard that path became. On 14 October 1899 a mining board decided to build the Auguste Victoria shaft site northeast of the village of Marl. Here quicksand full of water lay above the marl, and in September 1901 the water broke in. The ground was frozen so the shafts could get through, and production began in 1905. At the first shafts the map puts the top of the Carboniferous at about 470 metres below sea level. According to the official closure plan, the mine kept its water down at 1,090 metres below sea level by the end. On 18 December 2015 the miner Thomas Hahn handed the last piece of coal from Auguste Victoria to Minister President Hannelore Kraft.

The name at the last shaft

Franz Haniel died in 1868. His descendants carried on the business, and out of it grew the Gutehoffnungshütte. In 1921 this company began sinking a new colliery near Bottrop, and it took the family name, the Franz Haniel colliery. In 1974 it was merged with the Prosper collieries into the Prosper-Haniel mine. Shaft Prosper 10 finally reached 1,317 metres down, according to the official mine chronicle. From 54 metres without coal to that depth is the distance this one name travelled.

On 21 December 2018 seven miners at the Franz Haniel shaft site in Bottrop brought up the last piece of hard coal mined in Germany. They symbolically handed it to Federal President Frank-Walter Steinmeier. The piece weighs seven kilos and is roughly the size of a large shoebox, and in April 2019 it went to his study at Bellevue Palace. None of the official sources names the seven men, so we do not either. But the shaft site where it came up bears the name Franz Haniel, 184 years after the breakthrough through the marl.

Seeing it for yourself

You can walk into the beginning of this story. At the LWL Museum Zeche Nachtigall in Witten a 130-metre old adit leads into the hill. The museum opens Tuesday to Sunday, but the adit is not step-free. You can see the end of the story at Zollverein in Essen, a World Heritage Site since 2001, with its double headframe over Shaft XII. In Bochum the German Mining Museum stands under its green headframe. The demonstration mine beneath it is a reconstruction, 20 metres below ground, but it shows the work underground. Please check opening times before you go.

Old shafts and adits outside these museums are danger spots, even when they look harmless. Do not enter them, and respect any barriers. What this underground still means for the towns above it is the subject of our earlier post on the second world beneath the Ruhr. The orecast map shows which seam lines, shafts and spoil tips are recorded beneath any place in the Ruhr, and how certain each line is. Where nothing is recorded, it shows nothing. The video tells the whole story in thirteen minutes.

← All news