About 9000-8900 years ago the continental glazier melted and retreated from Tervola and Kätkävaara. The waters of Lake Ancylus then covered these areas.
During the Litorina Sea Kätkävaara was first an islet where the waves washed the fine soil with them, so that only a rocky field was left behind. This kind of a rocky field is often called the “Devil’s field” (Pirunpelto).
Along the footpath you can see several ancient shores moulded by different sea and lake phases. In rainy weather the rocky field is quite slippery due to the algae and lichen growing in it, so it is advisable to walk carefully in the “Devil’s field”. Mind the moving stones!