The eclogites in western Norway were formed when Precambrian basement rocks were squeezed and pressed down under great pressure deep under the Caledonian mountain chain. The process may well have triggered some of the deepest earthquakes the world has ever known. The clearest traces of this drama are found in and around Mt. Eldsfjellet, in peaceful Meland.
The mountains of western Norway are lovely to wander in. In Cambro-Silurian time it was the mountain itself that wandered. The mountain, or more correctly the bedrock, first moved eastward, then back a bit westward again. All this rocking back and forth in the mountains ended about 400 million years ago.
Siggjo is a cone-shaped, volcano-like mountaintop in the part of Hordaland where one finds the best preserved volcanic rocks. The rock types originate from one or several volcanoes that spewed out glowing lava and ash. But, the shape of the mountain, as it appears today, formed later and by completely different forces.
The highest mountainous area on Stord, including Kattnakken, Midtfjellet and Stovegolvet, has more in common with the mountainous terrain on the mainland than in the low coastal landscape of Sunnhordland. The volcanic bedrock together with the erosive powers of nature has resulted in a unique plateau landscape.
The type of underlying rock can be decisive for how many different types of plants are found in an area. In the area around Hamlagrø-lake the diversity is especially obvious. The geological conditions change much here within a short distance.