Tongrube

Gazing upon this unassuming landscape, can you imagine a time when the Tongrube echoed with the clang of machinery and the shouts of workers? This seemingly tranquil area in Hamburg-Hummelsbüttel was once a bustling clay pit, the Sievertsche Tongrube, providing the raw material for a nearby brick factory established in 1898. The Tongrube’s story, however, stretches far beyond its industrial past. It whispers tales of a time long before bricks and factories, a time when the Tongrube lay submerged beneath the waves of the Holstein Sea. This was the last time the ocean reached this far inland, during the second to last interglacial period. The Holstein Sea left behind its mark in the form of marine and terrestrial deposits. These layers usually remain hidden beneath younger sediments. However, the glaciers of the last ice age dramatically reshaped the land. They thrust these ancient layers upwards, creating folds and scales that brought the Holstein-era deposits to the surface. The Tongrube, through its excavation, revealed this hidden geological treasure. This made it a crucial site for Quaternary research. Scientists, like those mentioned in Averdieck’s 1992 study in Meyniana, meticulously examined the exposed layers. They pieced together the story of the region’s transition from the Elster ice age, through the warming period, and finally to the inundation by the Holstein Sea. This detailed sequence of events, visible in the layers of Lauenburger Ton, freshwater deposits, and Cardien sands, provides valuable insights into the climate development and transgression of the Quaternary period. Today, the Tongrube stands as a protected natural monument and geotop. The once-exposed geological marvel is now covered with a protective layer of soil. This shields it from the elements and preserves it for future study. While the main geological feature remains hidden, the area continues to thrive. Diverse plant and animal life has taken root in the calcareous soils. In the southern part, you might spot rare sedges, Centaurium, Leontodon saxatilis, Rubus saxatilis, Euphrasia, and Succisa pratensis. In the northern part, a small pond shelters one of only two locations in Hamburg where you can find the Schwarzwerdenden willow (Salix myrsinifolia). The Tongrube, though transformed, remains a captivating testament to Hamburg’s rich geological and natural history.