If you walk the tunnel leading East from the head entrance you will after  25 and 40 metres see fault lines in the limestone sloping 45° towards East. The fault lines are easy to find because they are filled with flint crossing the layered flint. Along those fault lines a displacement has taken place, the limestone east of the fault line having sunk 12 metres compared with limestone at the western side.

These movements were probably caused by the climate change at the end of  the Ice Age.During the Ice Age the water was periodically frozen not being able to dissolve the salt as the salt horst moved upwards. In the warmer climate after the Ice Age the ground water again started to dissolve the upper part of the salt horst causing the landscape to sink. The faults occurred when the limestone filled up the cavities created by the dissolved salt that was carried away by the ground water.