Om elve-erosjon og en isdemt sjø i Birtavarre-området, Troms.
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The geological survey in the Birtavarre region during the summer 1952 had as its main purpose the investigation of the copper ores of the district. However, some attention was also paid to geomorphological and quaternary features. Dr. H. Reusch, the director of the Norwegian Geological Survey 1888-1921 visited this region in 1901 and described the deep canyons and the great waterfalls, some of which are more than 200 meters high. One of them, the Helgafoss, has a free fall of water 146 m high. The minimum flow of water in this river, the Guolla Jok, is about 1100 liters per sec. Now, after 51 years, there is no visible change in the position of the waterfall, nor has any observable erosion of the flat-lying quartz-biotite-hornblende schist near the head of the fall taken place. The age of the canyons is still a subject of discussion. Reusch concluded that they were formed in interglacial time. The Guolla Jok comes from the lake Guolas Jvr, which is now proved to have been ice-dammed and larger in late glacial time. A pronounced esker leads from the lake up to the upper part of one of the canyons.