Hengjefjødd ice-age hike

Many stones lay on the surface of bogs, simply resting on the peat with no solid rock underneath. Farmers in norway will also find new stones in their fields every year. Why do these rocks surface?

Frozen ground expands and the rocks move up in winter. Then when spring comes and thaw sets in, the ground recedes, but stones tend to get hung up somewhat causing small hollows underneath them. These hollows of only a couple of mm get filled with surrounding soil and the stones never quite falls back to its original level. Thus over many years, the stones surface!

This is a typical U-shaped valley characteristic of erosion by glaciers. The strong baserock of the area consisting of granites and gneisses is polished smoothly by the ice.

This as opposed to V-shaped water-erosion valleys which you may have seen in other mountain ranges.

A moraine is any glacially formed accumulation of unconsolidated glacial debris (soil and rock). This debris may have been plucked off a valley floor as a glacier advanced or it may have fallen off the valley walls as a result of frost wedging or landslide. Moraines may be composed of debris ranging in size from silt-sized glacial flour to large boulders. The debris is typically sub-angular to rounded in shape.

There are socalled end-moraines shoved in front of the glacier, ground-moraines under the glacier and lateral moraines shoved to the side by the glacier. Here you are standing on top of lateral moraines.

Moraines are often nutrient-rich, well-drained and sandy substrates with their own typical flora and fauna.

A kettle hole is formed by blocks of ice that are separated from the main glacier - perhaps the ice front stagnated or retreated or perhaps ice blocks were washed out from the glacier during a glacier flood. If conditions are right, the isolated blocks of ice then become partially or wholly buried in outwash. When the ice blocks eventually melt they leave behind holes or depressions that fill with water to become kettle hole ponds or lakes. Often sediments fall off the ice block as it melt and collect around the sides, thus creating characteristic ringwalls around it.

The movement of glacier ice studded with rocks can generate a range of markings. Large blocks embedded in the sole of the glacier create grooves up to a metre wide and many centimetres deep. Smaller blocks and grit create parallel scratches or striae. Where a large, sharp edged block catches on the bedrock floor, pressure builds up until the rock fails, giving chatter marks or crescentic gouges. Here the basal layer of glacier ice is moving by stick and slip. Striated surfaces often show many parallel striae. Occasionally, a single surface shows crossing striae, indicating two different phases of ice movement.

Try to distinguish these ice age marks in the baserock here. Do not confuse them with quarts-veins and natural layers inherent to the baserock.

As the glacier retreated, big floods deposited large amounts of sediments in the valley bottoms, as happened here. Now a small creek meanders over the plained valley bottom.

You have now arrived at the public Stavskarhytta. You may stay here the night or just enjoy your lunch - there is a box for payments inside.

From the Stavskarhytta on, you leave the T-marked path and should rely on your GPS and sheep-trails for navigation.

The Setesdalsheiane highlands are characterised by oddly scattered boulders. Ice sheets have blasted them out from the baserock. As the glaciers moved slowly on top of these highlands and the baserock was hard (granites and gneisses), these boulders were not ground to pieces as in most other mountain areas. Rather, they were deposited locally - often slightly polished and rounded. Quite in contrast to the squared boulders you saw near the dead-ice kettles that have come off the face of the mountain in more recent time after the ice age.

When the ice melted and life returned, peat-moss (Sphagnum ssp.) soon colonised the moist shallows. Dying peat-moss is filled with water and does not decompose under low temperature anarobic conditions. The result is peat-moss growing on dead peat-moss, creating peat-soils eventually bogs.

Bogs are nutrient poor and often acidic environments storing water from precipitation. Even in very dry periods, these marches will be water-soaked.

Few species can live here, but peat-moss thrives. This is a great example of how a plant species manages to manipulate its environment to maintain and even create conditions favourable for its reproduction.