Devil’s churns

Due to their depth, three of these are counted among Finland’s largest potholes. The largest lies at the foot of the hill and has partly collapsed. It is 8 metres in diameter and 15 metres deep. Two other devil’s churns, with depths of 9 and 10 metres, are located on top of the rock face.

These potholes were created around 10,000 years ago, on the fringes of the melting continental ice sheet, by powerful meltwater flows which eroded the rock. Rocks and stones were swept away by fast flowing meltwater gushing through tunnels at the base of the glacier. In the case of Sukulanrakka, the meltwater also swept away the soil covering the rocky outcrops. As powerful eddies developed in the meltwater tunnels, the boulders carried by the flood began to swirl. Under the power supplied by the water, the rocks and boulders drilled down to the rock face underneath, creating round potholes known as ‘devil’s churns.’ Most of the rock material carried along by the meltwater accumulated to form a ridge running in the direction of the tunnel.