Our home, Plura, looks over the valleys of the ancient Scandes. This spectacular landscape and the mountain range rimming it originated some 400 million years ago when Greenland collided into Scandinavia. The collision resulted into a huge mountain range, higher than the current Himalayas. Called as Caledonide Mountains, the range reached from current area of Scotland to the Svalbard islands.

These are the insides of once huge mountains, as erosion has worn them down. The dinosaurs have been walking on this landscape, and many ice ages have carved the valleys into their current shape.

Inside these fells are huge deposits of limestone. The stone is made up of the sea floor that was pushed up by the moving land masses into the mountains. During the process, the limestone turned into layers of marble, creating favorable circumstances for acidic water to carve its way through the soft stone and form caves.

In this region of Rana there is about 200 known caves. Altogether there are something like 2000 known caves in Norway. Most Norwegian caves are relatively small, but the Plura system and Steinugleflåget are among the few exceptions. Plura is one of the biggest underground rivers in Norway, maybe in the whole of Scandinavia as well.

Steinugleflåget is a bit of a geological mystery. The collapse is going down at least 230 meters from the surface, taking in account the underwater part of the cave. To create a collapse like that there needs to be a cave beneath. It is not currently known how this kind of cave could have been formed.

Glacial ice has filled the valleys many times. Some of the caves in the area are older than the last ice age. During the periods between ice ages deposits of ice were preserved inside the caves. Analyzing these deposits, it can be learned how the temperatures have changed over not just the last 10 000 years after the last ice age, but even 700 000 years back in time.

Or imagine a bear going to a cave tens of thousands of years ago and dying there. It might be almost perfectly preserved, if circumstances are right. A cave can be like a time capsule, transporting information from the past.

The caves in this area are generally formed of marble. Marble is metamorphic (transformed) limestone. It has turned into crystals, like sugar. Caves in the Caledonian region are very beautiful because of the many colors of marble. The dissolution, or how the water is working with the stone, is very different from limestone. Also, the water being very cold, the chemical reactions are quite different from caves in e.g. Southern Europe.

Some mysteries remain. One of the questions in Rana area is that most of the caves are small, but a few are big. Why so? Maybe diving in the Plura cave will help us to answer that question one day.