𝑾𝒖𝒏𝒅𝒆𝒓𝒘𝒆𝒓𝒌 𝒅𝒆𝒓 𝑬𝒓𝒅𝒈𝒆𝒔𝒄𝒉𝒊𝒄𝒉𝒕𝒆 - 𝑲𝒖𝒈𝒆𝒍 𝒎𝒊𝒕 𝑺𝒄𝒉𝒂𝒍𝒆𝒏𝒃𝒂𝒖
Like a broken sphere made of concentric shells, a strange phenomenon has developed in the andesite rock of the Hellerberg. On the "Achatweg" in the quarry walls further outcrops with similar semicircular shapes can be discovered, although none is as impressive to look at as this one. The shape popularly known as the "Basalt Rose" raises questions, especially one. How did it come about? A special process of desquamation, which can occur in igneous rocks when the pressure is relieved, must first be considered as the cause of the phenomenon: the so-called exfoliation. Pressure relief occurs, for example, when the rock masses lying on top of it are removed by erosion or valley formation and the previously compressed rock underneath is freed from the load or the lateral pressure. This causes the exposed rock to expand somewhat, in the direction of the decreasing pressure. Fissures and fissures form parallel to the surface of the land, creating an onion skin-like appearance. Transverse stresses create additional cracks. Weathering can then model the shell formation even more concisely. Source: Text information board
𝐿𝑎𝑣𝑎𝑠𝑡𝑟𝑜𝑚, 𝐼𝑛𝑡𝑟𝑢𝑠𝑖𝑜𝑛 𝑜𝑑𝑒𝑟 𝑁𝑒𝑏𝑒𝑛𝑘𝑟𝑎𝑡𝑒𝑟?
It is questionable whether the phenomenon can already be adequately explained by the pressure relief. As is so often the case in nature, different processes overlap here too. It is obvious, especially in the case of an old volcanic landscape like the Hellerberg, that stress cracks were created while a flowing body of igneous melt was cooling, which later led to a platy-shelled secretion under pressure changes. The shape cut in the outcrop could originally have emerged from a small lava flow or an underground melt, an intrusion, perhaps also from a volcanic secondary crater. Source: Text information board