The eclogite in Trøsdalen formed when a dark igneous rock, typically basalt, diabase, gabbro or amphibolite, was transformed under extreme pressure and temperature conditions deep in the Earth’s crust. The occurrence of eclogite shows that the basement rock in the area was once pushed down to depths of between 60 and 100 kilometres. The formation of eclogite in western Norway is linked to the collision between the continental plates Baltica and Laurentia about 400 million years ago.
