The archipelago of Norway at the Skagerrak form a very relaxed landscape. The glaciers have not only smoothed the original rocks here, but also produced a special feature - large "Potholes (Jettegryte)" with circular, reflective water surfaces.
The largest pothole on this stretch of coast between Risør and Grimstad is called Jettegrytene på Fie. It is circular and has a diameter of several meters. The potholes are occasionally attractive bathing spots, because the water flowing in over the hot stone edges and the existing water are warmed up by the sun's rays. People like to swim in this pothole and we were lucky to be able to photograph it untouched.
These potholes are smooth and often cylindrical holes in otherwise solid rock. They form when a glacial river causes turbulent movement of rocks and gravel beneath its ice. The width and depth of the potholes varies from a few decimeters to several meters.
These potholes are formed where a rock (or many rocks) are spun around in the same spot by a circular vortex of water. The abrasion begins to erode bedrock into a hole. Once started, the feature even amplifies on its own as the hole increases in diameter, creating an increasingly stronger vortex. A stone thrown into the hole is called a grinder. When it wears out from the constant circular movement, another stone will eventually roll in to take its place.
A less common explanation for how these potholes form is that the cylinders are formed by cavitation beneath the glacier, when water pressure creates a temperature that then erodes the pot.
By the way, the name in Norwegian comes from Jette (troll or giant).
We enjoyed the days on the archipelago and used the large potholes for beautiful shots of reflections.