New knowledge about the shaping of Scandinavian landscape
In a new nature geoscience article Dr Philippe Steer, professor Ritske Huismans and collaborators shed new light to an old scientific controversy.
Steer and Huismans are both employees at the Department of Earth Science, University of Bergen.
We have asked them what this old scientific topic and controversy is all about, and what his and his co-authors' contribution is, with their new data:
Origin of a landscape - two different theories
The origin and fate of the western Scandinavian landscapes under the repeated ice sheets of the last 2.8 million years (Quaternary) is a highly debated scientific topic since a hundred years. One theory states that the fjords in western Scandinavia are mainly formed by glaciers and ice sheets, while the relatively flat top of the Scandinavian mountain range (e.g. as can be seen in Hardanger Vida, Dovre) was thought to have formed by eroding the 400 million years old Caledonian mountain range to sea level in Mesozoic times (100-60 Ma). As these flat surfaces are at present at elevations of 1-1.5 km, this was taken to indicate uplift to its modern elevation during the last 60 million years.
A completely different theory assumes that the high mountains in western Scandinavia/Norway have been there since about 400 million years, and were slowly eroded to their modern shape and elevation. In this latter theory, both the fjords and the high elevation flat morphology is thought to be formed by glaciers and ice sheets during the last 2.8 million years.
Controversy due to insufficient data
This controversy is to a large degree a result of insufficient data on the age of these different characteristic landscape features of the Scandinavian mountains, and highlights the difficulty in our ability to reconstruct the past.
The mountain range in western Scandinavia - a remnant of the old Caledonian mountain range
In our contribution we have, for the first time, managed to demonstrate that the glaciers and ice sheets have eroded both the Scandinavian fjords and flat high-elevation surfaces during the past glacial times. This supports the idea that the mountain range in western Scandinavian as seen today is a remnant of the old Caledonian mountain range and has been at high elevations ever since.
Linking onshore and offshore geology
This discovery was made possible because of the large amount of data available on the offshore of Norway, which allowed linking two fields, onshore and offshore geology that are usually studied separately. Because onshore erosion results ultimately in offshore sediments, it is fundamental to understand the past sediment record to assess the history of Scandinavian landscapes. The amount of offshore sediments resulting from glaciation during the last 2.8 million years have been compared to the maximum amount of erosion that has occurred in the fjord areas for the whole of western Scandinavia. The volume of glacial sediments observed offshore is much more than what can result by fjord erosion. This indicates that erosion must also have occurred in the areas above the fjords, e.g. on top of the flat surfaces and demonstrates that these high elevation flat surfaces characteristic of the Norwegian landscape are in geologically terms young.
The entire topography reshaped by glacial erosion
Our study supports the idea that the entire topography was reshaped by glacial erosion, and asks for a re-interpretation of the tectonic history of Scandinavia. This result has important consequences for oil and gas exploration offshore Norway as it aids in the reconstruction of topography in the past, and may also help to better understand past topographic and tectonic evolution of other less-well constrained glaciated areas, such as Greenland.
Read the complete article in nature geoscience.
Also read about this research in University of Bergen News.