Jökull

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Jökull - 01.12.1983, Qupperneq 96

Jökull - 01.12.1983, Qupperneq 96
the ice sheet of the central highland on the other can be clearly seen. On closer examination this difference is not only apparent in the large scale landforms but in the smaller ones too. A well dev- eloped roche-moutonnée landscape where erosion by a comparatively thick glacier has been very eff- ective is very widespread in Scandinavia and Can- ada, but in Iceland it is only found in Fljótsdalshér- að, in a small area in Borgarfjördur and a very few other areas. In the very same places very well deve- loped large glacial grooves (flutations) are also found such as can be seen in Fig. 7 which shows glacial grooves in the Sledbrjótur region in Hérad. Here a sinuous groove can be seen, a socalled “cave- tto“, a feature believed represent “highly plastic“ erosion (Gjessing 1965, 1966). Thissuggests that the erosive capability ofglaciers has been most in these areas, since as well known it depends mainly on the glacier thickness and the rate of flow. Widespread on the fjord pnomontories and mountain sides near the coast are to be found large, steep talus slopes, especially where characteristic features of marine erosion are dominant, as for ex- ample on Hvalnes (Fig. 6). Such screes are hardly found inland where glacial erosion features are dominant. Towards the top of the screes is a net- work of water eroded gullies, which are often tens of meters deep, so that the landscape there appears as a forest of pyramids (buttresses) uppermost in the mountain sides. (Figs.6 and 8). A number ofwater eroded gullies can be seen in Fig. 8, which extend side by side downslope from the corrie landscape farthest up the mountain. The talus, gullies and pyramids bear witness to very active water erosion and frost weathering of long duration. The position of these strongly water eroded areas on peninsulas and farther out the fjords slopes decidedly suggest that they have been subjected to little or no glacial erosion during the last glaciation and possibly oth- ers, since their position agrees with probable ice free areas, as they are shown in Fig. 4. Well developed glacial cols (Fig. 9) can be found widespread in the alpine landscapeand they give an idea of the thickness of the valley or fjord glaciers at their time of formation. Helgi Pjetursson (1906) and Trausti Einarsson (1959) have treated them in their work and the latter has pointed out that in some places they are found at two or more altitude levels. A rather thicker weathering cover is widespread above the main valley or fjord glaciation limits (Fig. 4) than below them, and all glacial erosional forms are considerably more subdued there. One of the Fig. 8. Northern slope of Nordfjördur from Odd- skardsvegur. At the top are horns, serrated edges and corries, which characterise the alpine land- scape. Below is a greatly water eroded gully slope. To the right is the serrated edge of Bagall and beneath Bagall corrie. In front of them is landslide debris and perhaps bottom moraine. It is likely that the gully walls were ice free during the last glaciation, but the thick till cover below them represents the glacial maximum. Smoke from capelin processing plant fills the valley floor. — Photo G. Sigbj. Mynd 8. Norðurhlíðar Norbjjarðar frá Oddsskarðsvegi. Efst eru eggjar, tindar og botnar, sem einkenna alpalands- lag. Neðan við er giljótt mjög vatnsrofin hlíð. Til htegri er tindurinn Bagall og undir honum Bagalsbotnar. Framan við þá er framhlauþsurð og e. t. v. botnjökulsruðningur. Líklegt er að giljahlíðin hafi verið ísvana á síðasta jökulskeiði, en þykk jökulruðningskápan neðan hennar sé jökulhámarkið. Reykur frá loðnubrteðslu fyllir dalbotninn. — Ljósm. G. Sigbj. clearest examples which I have seen ofthis is where the weathering cover thickness and glacially eroded forms become more subdued at 200-250 m a.s.l. at the Vatnsskard road to eastern Borgarfjördur. THE SOUTHEASTERN COAST FROM EYJAFJÖLL TO FLJÓTSDALSHÉR,\Ð On Fig. 3 it can be seen that the coastal moutains are almost everywhere formed by alpine glaciers and marine erosion is also well developed there. A survey of the glacially eroded landförms from Breid- dalsvík to Eyjafjöll reveals that glacially eroded val- leys and fjords are very poorly developed compared with Fljótsdalshérad and mid northern Iceland in 94 JÖKULL 33. ÁR
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