The bedrock consists of Småland granite. The loose strata are made up predominantly of moraine rich in boulders, which particularly in the upper layer often are large.
A small amount of ice river material occurs along the eastern boundary of the area. Exposed rock exists only on Idhöjden and in the area’s north-western section. The entire area lies above the highest coastline, which in this part of Sweden is about 135 metres above sea level. The moraine, therefore, has not been washed away by the sea.