Meltwater ridges, meltwater

channels or glacial grooves?

We’ll try to explain what is what among these three ice age traces.

In many places you see long, narrow meltwater ridges winding down the mountain slopes, more or less at a right angle to the contour lines. Fine examples are found on the western slope of Mount Fjätervålen and on the northern side of Grundagsvålen by Klutsjön.

The meltwater ridges were formed when sand, gravel and stones deposited in ice crevices where meltwater had run down the mountain slopes.

Meltwater channels also meander down the mountain slopes at a right angle to the contour lines. As the name indicates, they are formed as channels rather than ridges. It could be a ravine that starts for seemingly no reason and then continues towards the bottom of the valley. Where the channels have formed in solid rock, they look like deep cuts made by an axe.

The channels were formed where meltwater that had collected between the ice rim and the side of the mountain drained under the ice in so called sink holes. Meltwater rushed with tremendous force through large channels and crevices under the ice. Such large crevices were found closest to the melting ice front. By studying meltwater channels, scientists are able to determine the location of the ice at different times.

The glacial grooves look like wide, flat slanting ditches or terraces on the mountain slopes. They are not quite parallel with the contour lines, which differentiates them from old shorelines, which are exactly parallel. Fine examples of glacial grooves are found on the northern slope of Mount Store Svuku.

Meltwater ridges at Fjätervålen.Meltwater ridges at Fjätervålen.

Meltwater channels at Grövelsjön.Meltwater channels at Grövelsjön.

Photos: Kentaroo Tryman.
 
Gränslandet » Traces of the ice age » Meltwater ridges, meltwater channels or glacial grooves?