Traces of the ice
The latest ice age started around 115 000 years ago. The climate got colder, and several Ice sheets formed. Sweden, Finland and the rest of northern Europe were covered by ice when the Ice Sheet reached its maximum 18 000 years ago. The World Heritage area was covered by a 3000 meter thick ice.
Today’s landscape in the High Coast and Kvarken Archipelago has largely been formed by the Ice sheet. The two main processes responsible are the land uplift and the movement of the ice sheet over the land.
The Ice sheet was moving
This ice in the Ice sheet moved, because of its own weight, downward to the bedrock and from the centre out towards the margins. Stones were plucked and the soil was removed when the ice moved over the bedrock. The ice ground down the bedrock, while at the same time transported material to the ice margin. This material is what later became till.
Roche moutonnées and striations
One of the traces of the Ice sheet are striations. These can be found on bare bedrock in the World heritage Site. They are parallel grooves and markings that were worn in the bedrock when the ice sheet moved over it. These striations tell the direction the ice moved in. Some of the striations are hardly visible, while others are several centimetres deep. It is easiest to experience the striations when the sun is low, early morning or in the evening. In some places you can find two, or sometimes three layers of striations in different directionsThe ice sheet moved in different directions during different periods.
The rocky outcrops themselves were also formed by the ice sheet. They have one rounded smooth side, while the other side is craggy and uneven, where stones have been plucked by the ice. These rocky outcrops are called roche moutonnées or sheepbacks.
De Geer moraines and other moraine formations
Till consists of a mix of clay, sand, gravel and rocks, and is the soil that the Ice sheet left when it melted. Moraines are any accumulations of till, created by the ice sheet. Moraines are a unique part of the Kvarken Archipelago.
There are several different moraine formations in the Kvarken Archipelago. One of the more characteristic ones are De Geer-moraines. These moraine formations are named after the geologist Gerard De Geer, who was the first to describe them. The narrow De Geer moraines form fields of parallel ridges, where the ridges are located 50 to 200 metres away from each other. One De Geer moraine can be up to thousand metres long and two to five metres high. De Geer moraines are easier to experience when they are surrounded by water like in Svedjehamn in the Kvarken Archipelago.
De Geer moraines were formed at the sea floor in deep water at the edge of the inland ice. Streams under the ice carried boulders, stones, gravel and finer material towards the ice edge. Just outside the ice edge, the water stopped flowing and the mixed stone material built up into a De Geer moraine ridge along the ice edge. A new De Geer moraine ridge formed at the place where the ice edge had moved to when the ice melted or and iceberg broke away from it.
Boulder fields
In some parts of the World Heritage Site, boulders seem strewn across the area and form boulder fields. The ice sheet created or transported the boulders here during the latest Ice age and left them here when the ice sheet melted. Boulder fields are especially impressive in the southern parts of the Kvarken Archipelago, where the inland ice has left behind loads of different sized boulders.
Next chapter: the land uplift phenomenon
This World Heritage Site has the world’s highest coastline and its shorelines gain new land each year. It is all thanks to the land uplift. How does it work?