Sten – Norrbotten

I am the absolutely oldest stone here in the stone circle, about 2700 million years old. That is over half the age of the entire globe. I was formed during a time period in Earth's history called the Archean, which lasted from 4000 down to 2500 million years ago. So that's why I'm called an Archean gneiss granite.

Such very old Archean bedrock can be found up in Norrbotten county in the north of Sweden, it is the very oldest part of Sweden. The largest area of Archaean rocks, various gneisses, is found north of Kiruna and up towards Treriksröset. The same typa of bedrock continues into northern Finland and northern Norway. Rocks don't care about national borders, we existed long before these borders. Then there are some small areas with Archean rock types further south, near Luleå where I come from, north of Haparanda, and near Jokkmokk. The geologists believe that the Archean bedrock continues at depth to approximately a line from Luleå to Jokkmokk and further to the northwest, but for the most part it is overlain by younger rocks.

I'm quite gneissic, but I probably started as a massive (as the geologists say) granite formed from a magma that intruded the earth's crust and solidified somewhere at depth when it got cooler. As I said, this happened about 2700 million years ago. Since then I have been subjected to pressure and movements, perhaps in several rounds, until 1800 million years ago or so. That's how I got my gneissic texture, with elongated mineral grains. Above all, I look quite flaky, almost like schist. Must also have happened when the bedrock moved, I don't remember very well. But I am the oldest of the stones in the stone circle, yes I am one of Sweden's absolute oldest rocks.

Geologist Åke Johansson
Swedish Museum of Natural History