Hannmyrkullen

Cracks in the bedrock were scooped out to become valleys

Some 200-100 million years ago, Sweden was part of the supercontinent Pangea. Our country was positioned in more southerly latitude and was covered by desert. Many dinosaurs were adapted for life in a dry climate and perhaps some of these frightening giants were roaming the Ragunda valley in those days.

The dry and warm climate caused cracks to form in the flat rock, the peneplain. The weathering scooped out the cracks and formed valleys. The more hard-wearing sections of the bedrock were preserved as rounded or steep hills. Thus arose the undulating hilly landscape.

Peneplain – a flat stretch of rock

In these days the peneplain in the geopark consists of the high hilltops but in other places the peneplain may appear different. This is because the rock surface has been exposed to different activities.

In the crust of the earth there are areas or larger blocks of rock capable of moving upwards or downwards, straight or angled, towards or away from each other, because of movements in the innermost of the earth. A block pushed upwards will be exposed to faster and more aggressive erosion compared to a block that is pushed downwards and protected by loose deposits in the sea, for example.

The peneplain that can be seen in the province Västergötland, where the Platåbergen mountains ‘rest’ on the peneplain, was for a long period protected against erosion by a sea. The erosion-resilient rock diabase covered the tops of the hills and protected the more exposed species of rocks from erosion, leaving remnants called inselberg. In Ragunda there was no such protection, hence the weak zones were worn down and formed the hilly landscape.

Rocky slopes with loose stones

High up on the hill Hannmyrkullen you can see a ridge of stones. They fell down the slope as the mountain weathered. These are called scree slopes.