Alluvial fans in Langedalen expanded during glacier advance in late medieval and early modern periods

by Jacob Yde, June 28, 2023

Alluvial fans are a common landform in the valleys around Jostedalsbreen ice cap. A riverbank exposure in Langedalen near Veitastrond reveals insights into the history of the development of alluvial fans.

The river Langedøla meanders along the valley bottom of Langedalen draining meltwater from the Jostedalsbreen outlet glaciers, Langedalsbreen and Opptaksbreen, located near the tourist cabin Tungestølen and the village Veitastrond on the southwestern side of Jostedalsbreen ice cap. Along a section of its southern bank, the river has eroded into an alluvial fan below Opptaksbreen, exposing sediments deposited in the valley before and during the Little Ice Age glacier advance.

The river Langedøla in Langedalen. The outlet glacier Langedalsbreen is seen in the background (photo: Jacob Yde). 

The oldest sediments in the section are from the period 900-1250 CE (common era). At this time, a large, forested floodplain with willow (Salix) and Populus existed in Langedalen. Then, as the climate gradually deteriorated and the glaciers started to advance, more sediment was transported in the river Langedøla due to enhanced glacial erosion of the bedrock and re-transportation of glacier forefield deposits. Another consequence of the glacier advance leading up to the Little Ice Age maximum was the progradation of the alluvial fans along the valley side. This expansion of the alluvial fan below Opptaksbreen is seen as a sandy and stony layer of sediments at the top of the profile.

This study by Atle Nesje from University of Bergen and colleagues Denise Rüther and Jacob Yde from Western Norway University of Applied Sciences has been published in Boreas.

Riverbank sediment profile in Langedalen (photo: Jacob Yde).