The world’s second-oldest mountain range—formed recently
The mountains at Ringvassøya north of Tromsø are the world’s second-oldest mountain range, aged 1.7–3 billion years. When we know that the Earth itself is only about 4.6 billion years old, that’s a respectable age. Part of the bedrock of Northern Norway has been around for quite a long time, but its current look is the result of recent events, geologically speaking. Up to 40 ice ages, the last of which ended approx. 10,000 years ago, shaped and moulded everything we see around us.
Cratons and caledonides
Generally speaking, Northern Norway has two types of rock, specifically craton bedrock and caledonian mountains. The Baltic Shield is found largely in Finnmark and in the border regions of Troms, but it is also exposed in Lofoten, Vesterålen and on the islands in Troms County. The bedrock here is at least 1.7 billion years old – often much older – and it consists of granite and gneiss. The caledonian mountain range, which has since been ground down considerably, is a little over 400 million years old, and it formed by tectonic plates (you know, the puzzle pieces making up the earth’s crust) moving in from the west, folding over the craton layer by layer.
Younger rocks on the continental shelf
The bedrock on the continental shelf is much younger, and it consists of sandstone, claystone and slate. There are pockets of oil, gas and coal. Much of the Svalbard archipelago is an elevated part of the continental shelf, and the islands are known for their coal beds and abundance of fossils. Andøya also has a small area of coal and fossils from this younger geological period.
Ice ages in Quaternary
Over the last 2.5 million years, Norway has seen approx. 40 ice ages, the last of which peaked around 21,000–17,000[CA1] years ago. Inland Norway was covered by ice several kilometres thick, and cirque and valley glaciers sat between exposed mountain peaks, known as nunataks, filling up the coastal areas all the way out onto the continental shelf. Evidence left behind from these ice ages, especially the last one, can be seen all around us.
During the ice age, coastal areas were a patchwork of valley glaciers extending from the inland ice cap and cirque glaciers digging into the rock underneath. Mountain peaks poking up from the ice, so-called nunataks, became sharp and jagged as a result of frost erosion. Ice formed the jagged coastal and fjord landscape that is so typical of the coast of Nordland and Troms.
At Helgeland, there is 60 kilometres from the mainland to the outermost skerry, and between these two points there are upwards of 20,000 islands. From the air, it looks like a myriad flat islands. Here and there, characteristic mountains knowns as rauks rise several hundred metres toward the sky. Originally, this was flat and level land, formed by waves and sea ice being lifted up and down by the tides, eroding and shaping the landscape. Ice age glaciers later broke up the landscape into a labyrinth of islands and stretches of water. The strandflat is at its widest at Helgeland, gradually narrowing as it moves north toward the North Cape.
Moraines in the landscape
When the ice began to melt 17,000 years ago, the process was not linear. Some years the ice melted so fast that humans, who first settled here 11,000–12,000 years ago, would have been able to observe the ice edge retreat in their lifetimes. At other times, the melting slowed down, and the ice edge sometimes even advanced temporarily. One such advance happened approx. 12,000 years ago. When it retreated again, it deposited debris along a moraine ridge still visible today.
The enormous weight of an ice cap several kilometres thick pushed the land down, and when the ice melted, coastal areas were flooded. The land slowly rose back up, however, especially inland, where the pressure of the ice had been the highest. To begin with, this process was quite quick, but over time it tapered off. The fertile soil along the fjords of Nordland and Troms used to be the old seabed, which rose from the sea approx. 8,000 years ago. On the arid heaths along the fjords of Finnmark, where vegetation is sparse, we can still see where the old sea levels used to be as the land rose from the sea.