The Ice Age

From the time after the Silurian period, there are hardly any traces of preserved rock formations. However, from the Quaternary period, which is relatively recent in geological terms, some deposits have been found. These formed during the Ice Age when all of northern Europe was covered by a thick ice sheet several hundred meters deep. Beneath the ice, deposits formed, primarily the so-called pinn clay, which today covers large parts of Gotland's bedrock and is the island's most common soil type.

The massive ice sheet moved slowly forward, much like modern-day glaciers, carrying both large and small stones. These stones left deep grooves in the bedrock in some areas. Many of the larger stones were shattered during the 19th and 20th centuries, but two giant boulders, Bastustain in Rone and Silverstain in Lojsta, still remain.

When the ice slowly retreated northward around 15,000 years ago, the Baltic Sea was a freshwater lake called the Baltic Lake. Evidence that Gotland was entirely submerged at this time is clear, as the Baltic Lake's shoreline ridges can still be seen on the island's highest points.