How Fjärås Bräcka, the Fjärås Ridge, was created

Fjärås Bräcka is a glacial ridge formed towards the close of the last glaciation period.

The inland ice sheet had its maximum extent 20,000 years ago. Then the ice began to melt, moving slowly forwards and continuing to melt as it moved. The ice came to a halt at Fjärås 14,800 years ago. As the surface ice melted, huge rivers of ice began to flow, bringing along sand, gravel and stones that formed a ridge. By the time the ice had completely disappeared Fjärås Bräcka had been created.

Explore the ice tunnel

On the left you can see a long timeline that tells you about the two last glaciation periods and the interglacial period between them. The second most recent glaciation period took place about 250,000–135,000 years ago. It is called the Saale glaciation. A warmer period followed, the Eemian interglacial, about 135,000–115,000 years ago. The last glaciation period, the Weichselian glaciation, commenced 115,000 years ago and lasted right up until 11,500 years ago.

The ridge is today composed of gravel, sand, clay and water. Sediment particles are scaled according to size. On the right, inside the ice tunnel, you can see the Atterberg scale measurements and definitions:

Boulder > 600 mm
Stone 60 – 600 mm
Gravel 2 – 60 mm
Sand 0.06 – 2 mm
Silt 0.002 – 0.06 mm
Clay < 0.002 mm

Below the particle scale you can see two displays. Compare the stone with the insect in the upper display: Is it a stone or is it gravel? And compare the stone with the tractor in the lower display: Is it a stone or is it a boulder?

Before you leave the tunnel: Can you see what is hiding in the hole far down on the left?