Some parts of Medvednica rocks were formed by the deposition on the bottom of ancient seas, which dominated the Earth in the past. This is witnessed by the fossils of different marine organisms found in the rocks on different parts of Medvednica. Throughout the turbulent geological history, these seas receded and expended, became deeper or shallower, more or less salty etc. This means that the mountain was occasionally completely flooded, and sometimes it stuck out like an island surrounded by the sea or small lakes and swamps.
The rocks of Medvednica rose to their present position in the turbulent processes of rising and subtracting, folding and fracturing of Earth’s core, so Medvednica was actually born around 12 million years ago, when its present-day centre rose from the deep faults.
Due to its turbulent and diverse geological history, Medvednica boasts all three basic types of rocks: igneous (formed by the cooling of lava), sedimentary (formed by the deposition of fragments of other rocks or plant/animal debris in the deep seas) and metamorphic (made of both groups of existing rock types, subject to increased pressure and temperature).
The main body of the mountain is made of metamorphic rocks, mostly Greenschist. This rock has become a symbol of Medvednica and is featured on the facades of many buildings on the mountain, such as Tomislavov dom and the Chapel of Our Lady of Sljeme, Queen of Croats. Greenschist is now protected by law and its exploitation is forbidden.
Another well-known rock present on Medvednica is the Lithothamnium limestone. Along with Triassic dolomites, it forms a unique karst area on the west side of Medvednica. Even though karst phenomena are somewhat hidden under younger Holocene deposits and thick vegetation, many karst forms such as caves, pits, sinkholes and valleys are still visible. Karst field Ponikve is like a huge sponge from which streams emerge and then plunge back into, appearing and disappearing. The Veternica Cave, which boasts more than 7000 m of discovered canals and is one of the deepest caves in Croatia, was formed by water plunging through the cracks in the rocks of Ponikve area. Playful karst forms on Medvednica can also be seen in Horvatove stube and limestone Lipa-Rog area.
People have exploited this stone treasure since ancient times. The first quarries on Medvednica date back to the Roman period. Nowadays, out of 11 Medvednica quarries, only one is still active: Ivanec. Dolomite is excavated from this quarry. Apart from the Zagreb Cathedral, parts of Banski dvori (the seat of the Croatian Government), Mirogoj (Zagreb’s largest cemetery) arcades and many Zagreb homes were made of these rocks.
Abandoned quarries are often visited by scientists and nature loves because numerous fossils and minerals can be found there.
You can learn more about the complex geological history of Medvednica and its rocks and minerals from the geological column set up at the main entrances into the Park, on Bliznec and in Bistra. Different rocks that form the mountain were built into the column in chronological order, from the oldest (shales) to the youngest (Litotamnia limestone).
Educational trail Miroslavec is dedicated to the geology of the mountain. This trail leads from Šestinski Lagvić to Kraljičin zdenac. You can find stories about the geological history of Medvednica on numerous educational panels the Public Institution Nature Park Medvednica has placed all around the mountain.