The geology of the bedrock in the area between Karmøy and Kristiansund is the key to understanding the geological history of West Scandinavia.

The mountains are formed in several time epochs, and the marks left behind are clear when you study the landscape and the individual types of rock. The last ice age, which in geological terms was recent, removed all traces of the effect of wind and weather, and left a beautiful surface that was polished and ground down by the ice.

The fjords, which cut deep into the fresh bedrock, provide a unique view into geological history because they provide a continuous profile through the mountain massif. In this respect the fjords are important because they make it possible to investigate the bedrock, which has a very complex developmental story to tell.

Gneiss

The bedrock in the Geirangerfjord area mainly contains Precambrian gneiss from the Western Gneiss Region, and most of it is of igneous origin. Occurrences of coarse-grained granite gneiss features like a relatively uniform mass in the otherwise stratified and varied gneisses.

Mica and schist occurs in some places. These rock types represent sedimentary rock that was transformed into crystalline stone through metamorphism – high pressure and high heat.

High pressure, high heat

Various occurrences of eclogite and olivine rich peridotite are found locally. A large area in the East contains Augen gneiss with some quartzite, garnet mica gneiss and several fields of olivine-rich rock. This part of the mountain was pushed over the underlying gneiss through the Caledonian collision.

Unlike the Nærøyfjord area the bedrock in the Geirangerfjord area does not retain evidence of the Sweconorwegian orogeny (1130–900 million years ago), but the Scandian plate collision (a phase of the Caledonian mountain range folding, 420 million years ago) led to transformation of rock types under very high pressure and great heat.

Processes deep down

This geological process gave us eclogite, among other things. This is a rock that only forms under high pressure. It is a striking and rather unusual rock, which mainly consists of reddish to pink granite and green pyroxene (omphacite). Particularly interesting is the local occurrence of microscopic remains of the mineral coesite, which is a form of quartz that forms under very high pressure and moderately high heat (700 °C). This has occurred 100 km deep in the earth’s crust.

About 65 million years ago (in the late-Mesozoic period – early tertiary) there was probably nothing left of the high Caledonian mountain range. It had been eroded down, so the landscape in most of Norway was low-lying and flat, characterised by rolling plains with wide valleys and rounded hills.

During the early tertiary the area became tectonically active. The continents pulled apart, and a sea was created between Greenland and Scandinavia about 55 million years ago.

Rising of the land

The weight of an enormous ice cover had pushed the Scandinavian crust downwards, and when the ice melted and retreated, the great rising of Norway took place (throughout the tertiary 65–2.5 million years ago), with considerable displacement along the fault system parallel to the coastline.

The rising was uneven, and we got a high, mountainous area parallel to the west coast that gradually sloped off and became softer towards the low-lying areas in the East. The sloping of the land and the accentuated topography resulted in a strong increase in erosion by water, and the old drainage system was rejuvenated. The result was steep and deep river valleys. When the great inland ice appeared about 2.5 million years ago, the ice excavated deep and wide valleys.

Deep sediments

The fjords and the valleys extending up from the end of the fjord, were thus originally old river valleys from before the ice ages (usually V-shaped valleys) that the ice excavated and re-shaped into U-shaped valleys.

Today the fjords are generally narrow, steep and deep, usually with large basins and thresholds. The fjord basins contain sediment up to 300 metres thick, with a very slight slope of less than one metre per kilometre.

Erosion

Rising of the land after the ice has retreated leads to slow but visible changes along the coast of the fjords and causes development of delta, mainly be the end of the fjord (e.g. in Geiranger). In contrast to this there is the dramatic effect of erosion in deep crevices and gorges, rockslide and snow cover that create more obvious changes to the landscape.

These geological processes are partially controlled by precipitation (snow and rain) in the Atlantic climate in the west of Norway, and they make a more striking effort to shape the landscape. Still – most of the erosion that has taken place since the ice age has had a very local effect and compared to the ice ages rather small effect, so the landscape and fjords created by the glaciers are looking unusually good for their age.

The bedrock in the Geirangerfjord area mostly contains Precambrian gneiss from what was called the western gneiss region. Gneiss is formed by metamorphism – when rock is exposed to high pressure and high temperature. The western gneiss region is a typical example of how the earth’s crust has been forced down into the mantle – more than 150 km – and then to be lifted back up.

The bedrock in the area is the legacy of the many large tectonic periods that have built mountain ranges, swallowed and transformed rocks deep down in the mantle, lifted them back up to the surface where other forces such as air, water and ice have pushed, brushed and polished the landscape into what we can see today.

Old as the hills

Current knowledge shows that the oldest bedrock in the West of Norway must have been formed more than 1650 million years ago. But what has had most influence on how the bedrock in this part of Norway is composed today is the formation of the Caledonian mountain range about 420 million years ago. That is when a western continent (Laurentia) collided with an eastern continent (Baltica) and in the impact zone a mountain range rose up which we see the remains of here in Norway, in Great Britain, East Greenland and the East coast of North America.

Higher than the Himalayas

When the continents collided, the outermost edge of Baltica penetrated deep into the mantle below Laurentia, while the continental plate Laurentia wash pushed over and on top of the Baltic plate. In the impact zone the different rock types in the earth’s crust were folded on top of each other, and an enormous mountain range formed, which geologists think were greater and higher than the Himalaya mountain range is today. Since then this mountain range has been greatly eroded – the highest mountain in the Scandinavian caledonides is today Galdhøpiggen, which stands 2469 metres above sea level. Two thirds of the mountains in Norway are remains of the Caledonian mountain range.

The mountains above us – the rock beneath

On a regional level the Caledonian bedrock can be grouped into sheets of different rock types or rock strata. These formed enormous thrust sheets that were folded over each other and pushed hundreds of kilometres in over the Baltic plate. So the Scandinavian Caledonides are made up of thin widely extended nappes and thrust sheets. To understand how the mountains above us and the bedrock beneath us are created and formed, we have to identify the complex sequence of events leading to the various rock strata. We also have to understand how these strata are composed of rock types that are formed in very different circumstances, and therefore have their own different geological histories.

Gneiss – deep down and back up

The bottom layer of rock is called the western gneiss region. It dominates the region and represents a segment from the previous Baltic shield even if it dates from the proterozoic eon, and is thus about 900–1650 million years old, the rocks are greatly altered and transformed during the Sweconorwegian orogeny about 1000 million years ago and then the Caledonian orogeny about 420 million years ago.

The Sweconorwegian orogeny did not affect the northern part of the western gneiss region north of Geiranger.

The bedrock in the Geirangerfjord area mostly contains Precambrian gneiss from what was called the western gneiss region. Gneiss is formed by metamorphism – when rock is exposed to high pressure and high temperature. The western gneiss region is a typical example of how the earth’s crust has been forced down into the mantle – more than 150 km – and then to be lifted back up.

Spectacular rock

The highest pressure is registered in the coast region near Stad and towards the north east. Evidence of these processes is mostly based on rare finds of minerals such as diamond and coesite (a type of quartz that is formed under high pressure), which are only stable at extremely high pressure.

The bedrock further in the country also shows evidence of high pressure induced metamorphism, and the entire area is known for occurrence of eclogite, a type of rock that is only formed at high pressure. This is a spectacular and rather unusual type of rock, which mainly consists of reddish to pink granite and green pyroxene (omphacite).

Particularly interesting is the local occurrence, in the Geirangerfjord area, of microscopic residue of the mineral coesite, a type of quarts that is formed under very high pressure and moderate heat (700 °C). This has occurred 100 km depth in the earth’s crust. There are also several pockets of olivine rich peridotite over large areas of the western gneiss region.

International interest

The topography of the area combined with the fact that the bedrock contains solid rock formed under high pressure and ultrahigh pressure that are so much out in the open, gives cause for great international interest in carrying out a wide range of research to study the rocks.

Over the bedrock on the Baltic shield there are site specific remains of very thin cover sequence of quartzites and conglomerates overlain by metamorphosed shales and schists.

The Storfjorden extends about 150 km into the country from the Norwegian Sea at Ålesund and ends up in the tributary fjords Norddalsfjorden, Tafjorden, Sunnylvsfjorden and Geirangerfjorden.

The Storfjorden follows faults and fracture zones in the bedrock. These criss cross the landscape from the coast Up through modern history the fjord landscape has made lasting impressions on those who have visited the area. This shows the sun shining in Tafjorden. (Photo: Audun Skjervøy).
and inland from the coast, and this is what gives the fjord the characteristic zigzag shape.
At its deepest, the fjord is 679 metres deep – just north of where the Sunnylvsfjorden meets the Norddalsfjorden. Characteristic of this landscape are mountains that only stand 500 metres above sea level at the coast, but stand more than 1600 metres above sea level by Geirangerfjorden.

Waterfalls and valleys

Sunnylvsfjorden and Norddalsfjorden are 2 km wide, but the innermost end of these fjords, Geirangerfjorden and Tafjorden, are 1km wide. The steep mountain sides extend up to 1300 metres above sea level, and the many waterfalls – such as “The seven sisters” and “The suitor” are magnificent sights. Small glaciers on the mountains contribute to the dramatic image, and the clay-rich melt water colours the fjord turquoise.

There are many small valleys and hanging valleys between the high mountains, which give the landscape an alpine look. Along the fjord the characteristic mountain farms are seen in dramatic places. The deserted farms are testimony to the sparing use of natural resources in times gone by. The small buildings on the mountain sides along the fjord reinforce the impression of the scale of the landscape, and they are important to how we perceive this landscape.

Many of the hanging valleys going into the main valley bear traces of mountain farms, and some such summer pastures are still intact and in use in Herdalen and Dyrdalen.

Geiranger

Furthest into the Geirangerfjorden, where the Geiranger River runs into the fjord, is the village ofBrudesløret (The bride’s veil) is one of many powerful waterfalls thundering into the Geirangerfjorden (Photo: Finn Loftesnes) Geiranger. The settlement is concentrated in a very restricted area between the fjord and the steep mountain sides, towering high above the roofs of the houses, posing a risk of rockslides and snow avalanches. Further south the bottom of the valley is characterised by traditional agriculture with farmsteads and cultivated land.

The settlement and the evidence of human activities do not detract from the drama and the scale of this landscape. On the contrary, the humble tracks of humans reinforce the experience of this magnificent landscape.

Up through modern history the landscape has made lasting impressions on those who have visited the area, and many have recorded the experience through painting, photography, travel writing and scientific literature. This confirms the status of this unique fjord landscape.