When the land-ice melted away around 15,000 years ago, the entire Store Mosse area became an enormous glacial lake - Fornbolmen. The lake covered large parts of western Småland. Store Mosse and Bolmen are remnants of the vast lake.

When land uplift set in, the land slowly "tilted" over to the south and around 12,000 years ago the glacial lake dried up. Sand had been stored on the lakebed. The wind was given free rein and a system of flying sand dunes, known as rocknar, was formed. Then the climate became more humid again. Parts of the sand became swampy and peat mosses were able to establish themselves.

Peat turns into a raised bog

In swamplands, there is a lack of oxygen. Dead plants cannot be broken down into soil. Half-rotted, they are stored in increasingly thick layers and they form peat. Here at Store Mosse, the peat layers have grown for 8,000 years. Eventually, the peat layers reach above the water level in the ground. In a rainy and cool climate, such as here in the southern Swedish highlands, peat formation can also continue above the surface. The bog grows highest in the middle. A raised bog is then formed, which gets all its water from the precipitation. Store Mosse consists mainly of raised bogs but also marshes. Unlike raised bogs, marshes also get water from their surroundings.

Bedrock

Part of the bedrock consists of metabasite. It protrudes to the surface in some places, including on Lilla Lövö. Under Björnekullakärret there is a layer of limestone and the lime is spread up into the bog through the groundwater and provides the conditions for the lime-dependent plants to live there.