Jökull


Jökull - 01.12.1978, Side 6

Jökull - 01.12.1978, Side 6
Fig. 2. Lateral channels on Skálar. The channels incline to- wards Ábæjardalur. Mynd 2. Jaöarrásir á Skálum. Rásunum hallar inn í Ábœjardal. Djúpidalur A mounded ablation moraine runs across the entrance of the Djúpidalur valley in a lee position to the main glacier in Skagafjördur (Fig. 5). A little further west drumlins run paralled to the main valley. The ablation moraine is most probabiy a medial morainic deposit. Some 2 km north of the entrance of Djúpidalur another ablation till deposit is located at a little lower altitude. It is assumed to be a remnant of a lateral moraine, supposedly a continuation of the medial moraine at the mouth of Djúpidalur. Hlídarfjall Hlídarfjall (Fig. 6) is a mountain plateau at about 500—600 m altitude situated to the north of the mountain Ellidi (793 m) between the Austurdalur and Vesturdalur valleys. Along the eastern edge of this plateau deposits of esker ridges and mounds of ablation till cover the upper slopes down to Austurdalur and extend in the ice direction from Ellidi. The characteristics and the location of this deposit indicate medial morainic origin. A medial moraine was formed when Ellidi was emerging as a nunatak between the valley glaciers of Vesturdalur and Austurdalur. Downstream from Ellidi the junction of the two valley glaciers was lying on the east side of the water divide on Hlídarfjall because of the greater strength of the Vesturdalur valley glacier. The surface forms of this deposit grade from rather sharp crested esker ridges to irregular mounds, but on the surface only ablation till is to be seen. In one of the sharpest ridges, fluvioglacial gravel was found under a 0.6 m thick layer of ablation till and 0.3 m of stratified sand and silt. In the northfacing side of Ellidi, a lateral terrace forms the highest lying part of this deposit. The crest of this terrace is at 580—600 m altitude and falls 25 m/km northwards. To the north of the medial moraine, subglacial chutes were cut into bedrock on the Austurdalur side of Hlídarfjall (Fig. 6 and Fig. 7). The biggest of these channels run obliquely down the hillside and the upper end is carved into the slope which proves its subglacial origin. The upper end is bowl-shaped which may indicate that englacial meltwater was running down to the base of the glacier. The direction of this channel is guided by bedrock fractures and the ice conditions at the time of formation. If the three areas of medial morainic deposits are compared, the most conspicuous difference has to do with the material type and the surface forms. In the Vatnsskard-Sæ- mundarhlíd area most of the deposits are eskers of fluvioglacial material and only minor 4 JÖKULL 28. ÁR
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