Rakke

The peninsula southwest of Stavern is easily accessible by car and bicycle, offers good parking, and is also a nice stop if you’re walking along the coastal trail.

There are two major geological stories behind the beautiful landscape, with its smooth rocky outcrops, views of small islets and skerries, and vistas stretching southwards towards Denmark.

The bedrock at Rakke consists mainly of Norway’s national rock, larvikite. As far as we know, this special rock has only been found in Norway, in the area known as the Oslo Region or the Oslo Rift, of which Larvik is a part. The blue larvikite found in several places in this area is quarried and transformed into many different products. If you recognize larvikite when you’re traveling—in Oslo, London, Singapore, or New York—you can be sure it comes from Vestfold, and almost certainly from Larvik!

Larvikite solidified from molten rock deep beneath extensive volcanoes—not just a few years ago, but around 280 million years ago, when these volcanoes were active. The volcanoes themselves, and much of the lava that flowed from them, have been worn away by long-term weathering and, not least, by several ice ages. So, the rock surfaces here at Rakke have “moved” upwards through the earth’s crust, quite slowly!

The last 2.6 million years have been marked by many ice ages. We know the most about the last one, which ended around 11,700 years ago. Hundreds of meters of ice covered our land, and ice—and especially running water between the glacier and the rock surface—shaped, polished, and wore down the bedrock along the coast. Much larvikite disappeared with the ice; if you visit the west coast of Denmark, you can easily recognize both larvikite and larvikite’s lava, rhomb porphyry, on the beaches there.

The beautiful, smoothly polished rocky outcrops with almost organic shapes, potholes, and impressive glacial grooves in the rock are all thanks to the last millions of years of ice ages! And—the coastal landscape, like here at Rakke, is not a common sight globally—this is something worth preserving!

But why isn’t the larvikite blue here at Rakke, what happened to the volcanoes, and why were there volcanoes here in the “old days”?

About 300 million years ago, almost all the continents were joined together in the supercontinent Pangaea, and within this continent, a rift valley formed. Perhaps it resembled today’s East African Rift Valley?

In the Oslo Rift, volcanism occurred, both as large cone volcanoes and fissure volcanoes, similar to those we know from Reykjanes in Iceland. It was in connection with these fissure volcanoes that larvikite was formed. Far below the volcanoes themselves, there were large amounts of molten rock or magma. A special lava flowed from the volcanoes, which eventually solidified into the rock called rhomb porphyry. But deep down, the molten rock slowly solidified into larvikite, in the magma chamber beneath the volcano.

So, what is so special about larvikite?

Rocks consist of various minerals, but larvikite consists almost exclusively of minerals from the feldspar group. In the Oslo Rift, crystals of several types of feldspar formed in some places. In the Larvik area, some of the magma chambers solidified with many such “twin feldspars.” If you’re lucky and see the rock in the right cross-section, it’s clear that larvikite can have a beautiful, bluish sheen. And blue rocks are not very common!