Schevenhütte Quarry

Geologically, it is part of the outermost foothills of the Venn saddle, where very old rocks from the latest Ordovician period are exposed.

Basically, the stone from the middle and upper Wehebach layers was roughly processed and sold on site.

With the end of the swamping in the quarry basin, an endorheic small lake developed over time and the open quarry slope in the east suffers greatly from the lack of supporting rock, which repeatedly causes rock slides, landslides and mass movements.

Today, the quarry is a registered soil heritage site of the Kupferstadt Stolberg because of its outstanding role as a teaching and research object.

The site is owned by Laufenburg GmbH and may not be entered due to the acute danger to life caused by the rock slides.

[2] The age is 490 million years, whereby the determination can be made relatively accurately by the fossil of the graptolite species "Dictyonema flabelliforme".

The greener variety is also called banded shale and is dominated by fine sand- and silt-streaked mudstones, in some of which sandstone beds can be found.

The strata of siltstone and banded schist found here show weak bending of their bedding planes in contrast to the shale-sandstone sequences along the road.

In addition, an old Roman road coming from Kornelimünster ran through Schevenhütte, up through the Wehe valley to the Rennweg in the direction of Düren, which still exists today.

In Schevenhütte the conditions were very good due to the water power of the Wehe stream, the forests of the Eifel and the ore and stone deposits.

It is certain that the quarry was used to procure building materials for the forester's lodge (today Nideggenerstraße 99) near Helenasruh, which was built in 1852.

Due to poor rock properties, the quarry never became economically viable and mining ceased again a few years later.

[6] Another attempt at expansion occurred around the same time near the present-day water treatment of the Wehebachtalsperre in the form of the Schwontzen quarry.

The red colour is due to an increased manganese oxide and haematite content, which in turn were caused by submarine volcanic ejections and could sediment particularly well at this location.

Individual layers of fine sand wedge out of the banded shales, creating a characteristic flashlayer.

Due to their good splitting properties, the broken blocks were mostly used as pavement slabs or low precision cut construction methods such as dry stone walls.

[6] Even in the Middle Ages, therefore, the slabs were quarried using simple tools such as pickaxes and crowbars, and prepared for use in a rudimentary way with chisels, fistfuls and lumps.

Towards the end of the 19th century, the stone in particular was worked somewhat finer and shaped into elongated cuboids for buildings and used in irregular masonry.

Large parts of the site are now sprayed with graffiti and the tools were either looted or destroyed with great force.

The warmth and the dry rocks in combination with the lake provide a good habitat for grass snakes.

At the transition between the lake and the factory site in the north-east, there is a wet, very shallow reed area due to the high water level, in which several toad species live.

In the first years after closure, the rocky outcrops were home to an eagle owl, which, however, can no longer be found there due to vandalism and constant disturbances.

The eastern wall can be divided into three areas due to anthropogenic interventions and natural conditions: The southern rock wedge between the southern and eastern break-off edge consists of strongly sandy mudstones and was therefore not worth quarrying.

The large east wall, the most prominent feature of the quarry, was in danger of collapsing soon after closure.

Small rockfalls occurred several times and a cone of debris already formed at the foot of the steep face, protruding from the approximately 15-metre-deep lake in the quarry basin.

Here, the most obvious tilting movements of the steep face could be seen, which formed a 5–6 m wide and 60 m long break-off area.

The crack in the top of the rock was so strong that it was even clearly visible in the digital terrain model (DTM) with a resolution of 1 × 1 m. The height of the break-off area went down to the next stable layer of clay shale about 20 m from the ground level.

Even though the large gap had withstood the extreme stress of the great flood in July 2021, the rock edge was still blasted as a precaution.

Due to the lack of supporting rocks, parts from the north of the east wall are caving in and threatening to fall.

Two blocks, each about 4 m long and 3 m wide, have already sunk several centimetres from the top of the rock and are completely surrounded by fissures several metres deep to the east and north.