Šmarna gora and Grmada are made of sediments that appeared in the deep water. The sediments that were brought by rivers and winds have hardened into layers of limestone, dolomite and claystone slates. In the following foldings of the Earth's crust, the layers have risen from the water, the sea withdrew, in the warm climate the superficial and flowing waters have eroded and formed the surface.
The geologic grounding of the lower part of Šmarna gora and Grmada is made of carbon claystone slates, in the middle Permian sandstones and sand slates. In the upper part the foundation is of Triassic dolomite, and in some places also limestone. Also the slopes are conditioned with the geologic foundation. The Western and the southern side are of dolomite with typical pyramid prongs. From the upper parts the dolomite gravel is pouring as well as bigger rocks. The gravel reaches far down the hill, so that it is covering the Permian and also carbonite stone laying down the hill. At the foot of the hill there are diluvial layers, sand and at some places conglomerate, on the plain around the Gora also alluvium, sand, mud and clay.