Jezersko has a very diverse geological history. 400 million years old rocks that once formed coral reef can be found around Vrinikov Grintovec, Pristovški Storžič and Stegovnik mountains. These are the oldest rocks in the area followed by some tens of millions of years younger shales, greywacke and breccia. The Triassic era was the time of explosive volcanic activity with its traces found around Štularjeva planina mountain plateau, represented mostly by acidic extrusive igneous flint-porphyry and flint-porphyries. The Kamnik-Savinja Alps were created with accumulation of sediments in shallow sea 200 million years ago and were pushed out of the sea around 60 million years ago by strong forces created in the Earth’s interior. Today’s form of the Kamnik-Savinja Alps was shaped mostly by glaciers from the last Ice Age that disappeared after the warming up of climate more than 10 000 years ago. Ground rocks of Jezersko area are mostly impermeable what enabled water from melting glaciers to cover the bottom of the valleys and consequently forming a big glacial lake. After the huge earthquake in 1348 lake water started to drain. (SOURCE: Bavec et al. 2009. Geologija Slovenije = The Geology of Slovenia.Ljubljana, Geološki zavod Slovenije: 612 pg.)