When it comes to the Goričko region, the geological history is quite as interesting as the geological composition. Almost the entire territory of this part of Slovenia is covered with tertiary rocks, which are between 66 and 1.6 million years old. The oldest rocks are found in the small area around Sotina and Serdica. They are classified as phyllitoid schist shales. Nowadays they visually emanate from the softer tertiary sediments and form the highest hills and steepest slopes of Goričko.
The formation of ancient metamorphic phyllitoid shales was followed by a longer geological period of continental land. It was not until the end of the Oligocene, about 23 million years ago, that this region sank once again and got flooded from the east by the Pannonian Sea. Only the most northwestern and the highest part of the region, the area around the Sotina, remained non-flooded. The sea covered this area for another 18 million years. During the Miocene and Pliocene, the original marine sediments got deposited (gravels, sand, and clays) and transformed by pressure and time into todays sedimentary rocks (Miocene limestones, sandstones, marls ).
With the increasing fluvial outflow, the sea started to lose its salinity. At the same point, the Pannonian Sea started moving more and more eastwards due to the rising of the surface on the west.
About 1.6 million years ago, during the Upper Pliocene period, an active volcano formed near Klöch, Austria. The consequences of its activity are also noticeable at the village Grad, where layers of basaltic tuffs and tuffits appear in partially coated layers of quartz gravel, sand, marl, and clay. The blackish basalt can be found also southwestern from Kaniža, Hungary. These rocks were used as a building material in the past. Nowadays they are also interesting from the mineralogical perspective, due to the high content of olivine nodules within them, especially since the Grad area is the only known Slovenian source of olivine minerals.
In the present Holocene epoch the area has been influenced by the accumulation of fluvial sediments in the valleys and slowly lowering the hilly surface by fluvial erosion.
In the past, the Goričko was well known for its clay deposits, which most certainly affected the occurrence of pottery. The heritage of pottery can be seen in an exhibition on Grad castle, todays pottery craftsman can be found in Pečarovci and Filovci village.