Boulder trail – erratic stones

Erratic stones are the pride of the Baltic Sea countries. When after the last Ice Age the land was freed from the huge glacial ice, it was also relieved from enormous pressure. The ground slowly began to rise – a process that is actually ongoing today. At the same time, the melting water of the ice first formed the Baltic Ice Lake and later the next development stages of the Baltic Sea – the Yoldia Sea, the Ancylus Lake and the Litorina Sea.

Erratic boulders like the granite porphyry you’re studying right now have witnessed all the development stages of the Baltic Sea over the past thousands of years. 

What makes this particular rock special is the fact that the large feldspar crystals found in it look like they’re suspended or floating within the rock’s finer mass. If this rock were a cookie, the red feldspar crystals would be individual chocolate chips inside it. The name rakakivi comes from the Finnish word “rapea”, which means fragile or crumbling. As the name suggests, this stone is quite fragile and crumbles much more easily than normal granite. Therefore, rapakivi stone is not a particularly good choice for a sauna heating stone, for example.

Did you know that more than half of Estonia’s giant boulders are of the rapakivi granite type? Pretty cool, right?