Vorstens badkar
Prästens badkar (German: Des priest's bathtub) is a unique geological formation from the Cambrian . It is a fossil sand volcano, which is located on the Baltic coast near Vik ( Österlen ).
This sand volcano consists of 500 million old sandstone . The original sand was saturated with water, had a low bulk density and lay under a water-impermeable layer (clay). A tectonic event put the soil under stress. Since water is incompressible, pressure is exerted on the ground in all directions, creating excess pore water pressure. The soil, which previously had a solid structure, is thereby liquefied, which means that the shear strength drops sharply.
This pulpy soil can then be pushed through the hanging water-impermeable layer. This leads to the formation of a formation that is very similar to a volcanic cone .
The pulp comes to rest on the surface and water and sand separate again ( thixotropy ).
Over time, the sand was covered and, in the course of diagenesis, turned into sandstone.
The trace fossil Diplocraterion parallellum was found in the sandstone .