Rovaniemi’s bedrock

The rock types in the vicinity of Rovaniemi belong to the Southern Lapland schist area known as the ‘Lappish triangle’. Originally, its rock types were layers of sand, clay and chalk, and volcanic lava and ash, which stratified two billion years ago on top of an older area consisting of two-and-a-half billion year-old granite gneiss.

These deposits folded and recrystalised about 1.8 billion years ago. The layers of sand formed quartzite and arkosite, and the layers of clay, mica schist. During the folding process, molten magma penetrated into it, crystalising as granite and coarse pegmatite seams. Later, quartz crystalised in the rock crevices, as white, linear seams, sometimes several meters thick.