By Inge Aarseth
The 17-km-long Nærøyfjord, innermost in the 204-km-long Sognefjord, is one of the wildest and most impressive fjords in the world. The fjord is extremely narrow and steep-sided with mountains and glaciers towering 1700 metres above sea level on either side. At its narrowest point, the fjord is only 250 metres wide.The oldest rocks in the area around the Nærøyfjord were created during the Precambrian Age more than a thousand million years ago. Around 425 million years ago, the North American and European continents collided, and the Caledonian mountain range was formed. The rocks were exposed to high pressure and high temperatures and were transformed, creating different rock types. The predominant rock types in the area are mangerite, gabbro and anorthosite.
During the Tertiary period, between 66 and 2.5 million years ago, the Norwegian mountains rose and the rivers started carving out valleys. During the Quarternary period, (the last 2.5 million years) there have been 40-50 ice ages in Northern Europe. Glaciers have gouged out the valleys, making them deeper and wider, and later gouged deep troughs below sea level. When the glaciers melted the sea filled these troughs, creating fjords. During the last Ice Age, from around 115,000 to 10,000 years ago, the glacier that covered Scandinavia was up to 3,000 metres thick and the land was pressed down. When the glacier calved and receded, the edge of the glacier was for a period where Bakka is today, and a moraine ridge was formed, which is why the fjord is particularly shallow there. At the mouth of the Jordalen valley, it also deposited gravel in a delta out in the fjord, which shows that the sea level at that time (11,000 years ago) was 110 meters higher than it is today.
The “Sogneelva” river and the great river theft in the Nærøydalen valley
The Sognefjord is the largest fjord in Western Norway and, prior to the ice ages, the biggest river in the area flowed westwards through the “Sognedalen” valley where the fjord is now. In inner Sogn, there were many tributaries that flowed into the “Sogneelva” river. Traces of these rivers can be seen today as side valleys high up in the mountains. The sources of the tributary that flowed where the outer section of the Nærøyfjord is now were up on “Skammedalshøgdi” (1600 metres above sea level), east of Gudvangen. The watershed between Sogn and Voss was up in the mountains directly west of Bakka. When the ice ages started, the glacier in “Sognedalen” became much larger than the glacier that covered the valleys in Voss. It effectively carved out the Sognefjord to a great depth over many ice ages. The sea thus eventually came to extend all the way to Gudvangen, while the rivers that flowed towards Voss did not reach the open sea until Bolstadøyri. The Nærøyelvi river thus came to fall steeply, digging more quickly into the rock bed. As the rivers dug further and further back into the valleys, the Nærøyelvi river overtook the Vosselva rivers one after another. These tributaries therefore abruptly changed direction and flowed in the direction of Sogn.
Before the ice ages (around two million years ago) the rivers in the mountain areas around Stalheim, Gudvangen and Bakka flowed in the direction of Voss. During the ice ages, glaciers carved out the Sognefjord and the Nærøyfjord and “stole” these rivers, so that today the watershed has moved from the area north west of Gudvangen almost all the way to Oppheimsvatnet lake. We can see that both the Jordalselva and the Brekkeelva rivers turn sharply when they meet the Nærøyelvi river.
Previously (before the ice ages), the watercourses above the waterfalls flowed towards Voss. The glaciers in the Sognefjord and the Nærøyfjord dug their way back into the mountains and “stole” the rivers, which is why they now form waterfalls running down the steep mountain sides.