Geology​

​

The centerpiece of our exhibitions is the geological exhibition in the Otto-Torell-House with its curved roof and glass front, also known as the House of Stones. It bears the name of the Swedish scientist who, exactly 150 years ago in Rüdersdorf, was able to prove his theory about the inland glaciation of Europe during the ice ages. There is a comprehensive exhibition here that clearly explains many aspects of Rüdersdorf limestone: How was the limestone formed? What happened during the ice ages? And how did Rüdersdorf develop in connection with open-cast mining? Explore how exciting the history of our Earth is here! It has left us many witnesses in the Rüdersdorf rock – including early dinosaurs, ammonites, and, of course, vast quantities of shells.

 

In front of the building is a slanted stone wall that runs parallel to the sidewalk. Its structure helps to understand how the geological units lie beneath Rüdersdorf. The cross-section shown depicts deposits from the last 250 million years – a mere blink of an eye in geological terms. The largest part is made up of the Middle Muschelkalk units. They are around 250 meters thick and were formed around 245 million years ago, during the Triassic period.

​​

In the North German Plain, these limestone layers are normally at least one kilometer deep in the earth—and largely horizontal. The top layer of soil there is up to a thousand meters thick. It was formed during the last ice age, in the Pleistocene, the most recent geological epoch, which began only two and a half million years ago.

Beneath Rüdersdorf, a salt dome is pushing upward. Over millions of years, it has gradually pushed the otherwise very deep limestone layers to the earth's surface. The uppermost part of these layers therefore peeks out of the ground in Rüdersdorf and is thus easily accessible. The rest disappears underground on the northern side at an angle of about 20 degrees, where mining would be too costly.

​​​

But how did these 250-meter-thick stone massifs form in the earth? The limestone layers are known as “Muschelkalk” (shell limestone), a name that refers to their origin: they are the remains of countless marine animals that were deposited here in ancient times. Around 245 million years ago, when today's continents still formed the supercontinent Pangaea, the whole of northern Germany and Poland were part of the Germanic Basin. This low-lying plain, which was then located in warmer climes, was flooded by the ancient Tethys Ocean. The water in the Germanic Basin was relatively shallow, similar to today's Baltic Sea. The climate was warm and dry, similar to that of North Africa today. The shallow waters were teeming with life. All these sea creatures used the calcium carbonate present in seawater to build their shells and skeletons. These calcareous body parts remain behind when the creatures die. The calcium carbonate thus consists of the remains of myriads of dead animals. This resulted in an almost unimaginable amount of limestone sediment, which was deposited on the sea floor over a period of around 8 million years, mixing with other sediment, namely clay, which was carried from the mainland into the sea. Every ten years, the limestone sludge grew by an average of one millimeter, resulting in deposits of six to eight hundred meters over time. The entire process took place during the Triassic period. In the following geological eras, the limestone deposits were covered by new layers of earth. High pressure over millions of years and temperatures of up to 200 degrees Celsius in the earth's crust ultimately led to the formation of limestone. It was compressed to a thickness of up to 250 meters. Here in Rüdersdorf, these limestone layers are now at the earth's surface because the salt cushion beneath them is pushing upwards. Where the resulting pressure from below is strongest, the limestone protrudes furthest from the earth and can therefore be easily mined.

​

The Ice Ages of the Pleistocene and Otto Martin Torell

But you can also learn more about much more recent periods in geological history in our geological exhibition: the Ice Ages and their legacy. Swedish geologist and ice researcher Otto Martin Torell had already completed many expeditions to inhospitable polar regions before he made a groundbreaking discovery here in Rüdersdorf in 1875. Torell realized that the gouges and scratch marks on the surface of the limestone must have been caused by glaciers. He was familiar with these glacial gouges from his homeland, where stones and debris at the foot of the mighty ice fields have left such marks since time immemorial. This laid the foundation for the realization that glaciers had grown from Scandinavia to Central Europe during the ice ages.

There was an abundance of rock from the north, including from Scandinavia, but until then no one could say how it got there. The best explanation previously offered was the idea of one or more overwhelming tidal waves that could have washed the debris from the north into the local area. After Torell's discovery, it was realized that the stones had been pushed to us by glaciers. Accordingly, the entire surface from Scandinavia to far into the northern European lowlands must have been covered by ice.