The limestone mountain at the Östbjörka nature reserve is made up of limestone formed by coral animals in the sea that covered the Siljan countryside just over 400 million years ago. Here are leafy spruce forests that are rich in flowering herbs, lime pine forests at the heights and in the hillside remnants of lime kilns used to make cement from the lime.
The traces of the meteorite strike can be studied in the limestone quarry in the eastern part of the reserve. Here you can see vertical limestone layers of different origins and a thick layer of impact breccia. At Östbjörka there are also landforms and soils that describe the development of the landscape from the latest inland ice.
Melting water from the inland ice has formed a ravine in the limestone. This meltwater drain is part of the meltwater drainage system from the recent inland ice melt. This drainage system is seen as a large number of gutters, which radiate into a common drainage channel at Östbjörka.
The meltwater drainage has largely occurred under the ice. Where Gryssbäcken goes today, the melt water has first flowed in a wider stretch (100 m wide and 10 m deep gutter) and has not deposited any material. Further down the ice river sand has begun to be deposited and here you are probably now off the ice edge.
A smaller delta with a beach hook is found in the valley's extension. The shore represents the level of the highest coastline at 208 m above sea level. On the delta plane, at a later stage but shortly after ice melting, flying sand has been deposited and a sand dune has also been formed. The original delta has largely been eroded by subsequent water flows as land elevation has caused the erosion base to be successfully lowered.