The antique mountain peaks of Svalbard
Top image: Alpine mountains in northwestern Svalbard. Photo: Endre Før Gjermundsen/UNIS
The steep, rugged mountains of northwestern Svalbard are much older than previously assumed and not the product of the latest ice age erosions. Instead, new findings by UNIS scientists indicate these mountains were formed much earlier and were protected by a glacial armour for the past one million years. This turns current knowledge about alpine topography development on its head.
17 September 2015
Text: Eva Therese Jenssen / UNIS
Glaciers are the most effective erosion agents and can change a flat landscape into an array of valleys and mountain peaks. In school we learn that the deep fjords and high peaks in many mountainous areas are caused by the several ice ages the Earth has gone through. Each new ice age has “washed out” evidence of previous glaciation periods.
Glacial “buzz saws”
Glaciers are known to act like “buzz saws”, limiting the mountain height. As mountain chains rise, the glacial buzz saw erodes, thus limiting infinity growth. Current consensus has been that the high-relief mountain landscapes are the product of repeated glacial erosion over the complete Quaternary period of the past 2.5 million years.
The team of scientists from UNIS, University of Buffalo, University of Bern, Swiss Federal Institute of Technology in Zürich, University of Oslo and University of Gothenburg, recently published their contrasting findings in the prestigious Nature Geoscience.
The scientists spent several months on field campaigns in remote areas of northwestern Svalbard. Isotope tests dating of the bedrock surfaces using 10Be (Beryllium), and 26Al (Aluminium), was performed on rocks sampled from eight alpine summits. The results show that these seemingly fragile mountain summits had been shielded from erosion.
Armour of ice
The “glacial buzz saw” impact on these Svalbard mountains was minimal as the mountains were protected by an armour of ice for the past 1 million years. As the last ice ages progressed, glacial erosion in the Arctic became less efficient and steep alpine landscapes were preserved by an glacial armour. The Svalbard summits, along with reported findings of older sediments in a fjord valley, show that this area experienced little glacial erosion in Late Quaternary.
On the contrary, the previous landscape has been preserved explains UNIS scientist Endre Før Gjermundsen, lead author of the paper.
– Our data show that these seemingly “young and fresh”, high-relief landscapes actually are conserved landscapes from long time ago. A blanket of ice has protected the shape of the landscape and conserved a much older topography, he says.
The scientists propose that the ice covering the Svalbard summits switched from an erosive ‘warm-based’ mode to a ‘cold-based’ mode that conserved the landscape. The concept of cold and warm-based ice has long been known to scientists, however, up till now cold-based ice has mainly been coupled to low-relief upland surfaces lacking in alpine glacial shapes, says Gjermundsen.
– For the first time in the northern hemisphere we are able to show with the combination of the two isotopes that alpine mountains were protected from atmospheric weathering and glacial erosion for the majority of the last million years, says project leader Anne Hormes from the University of Gothenburg and UNIS.
– Our research shows that the glacial erosion processes are much more complex than we thought. It seems that the glaciers have exhibited a “bipolar” behaviour, both as an erosive agent, but also as a conserving agent; even in alpine areas we thought were most prone to erosion, says Gjermundsen.
These new findings open up for more investigations in other areas with alpine landscape features like the third pole of Himalaya.
Gjermundsen, E.F., Briner, J.P., Akçar N., Foros, J., Kubik, P.W., Salvigsen, O. and Hormes A.: “Minimal erosion of Arctic alpine topography during the late Quaternary glaciations”. Nature Geoscience, September 2015. doi: 10.1038/ngeo2524
Endre Før Gjermundsen, firstname.lastname@example.org