Nice Gneiss!

Nice Gneiss!

This is part of the old Pangaean landmass dating from pre-dinosaur times. Since then, the world split apart into the modern continents which spread about the globe, and some of them collided against each other again. When the Pelagonian fragment was hit by Africa, it was run over, and went down to a great depth in the earth, say, about 25 - 30 km. But then, seeing that it is a lot less dense the surrounding material down there, it came back up again, a process called exhumation. See all those folds in the rock? These are the well-earned battle scars of a rock that has spent much of its existence getting deformed. And now here it is, nicely sliced up on a bookcase in my office.