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Thursday 1 February 2024

Glama, NW Iceland -- after the ice cap

This is an extract from the old topographic map of NW Iceland, showing the Glama Plateau, on which there was, once upon a time, a small thin ice cap. It's clear from the radiating pattern of spectacular outlet glacier troughs (fjords) that this ice cap has come and gone many times, and that it has had prolonged phases of intensive glacierization.

False colour image of the Glama area withy a thin seasonal snow cover.  It shows up rather well the plateau on which the small ice cap existed......

It's been a pleasure to come across the digitized version of Eggert Larusson's doctorate thesis from 1983 -- thanks to the Durham University digitisation programme.  Eggert worked with us in Iceland in 1973-1975, and I supervised him as a research student before I left the university in 1977.  He was able to incorporate a lot of the work done on the Durham University Vestfirdir Project -- and it was great to see so many research strands pulled together in Eggert's big thesis.

Larusson, Eggert (1983) Aspects of the glacial geomorphology of the Vestfirdir Peninsula of northwest Iceland with particular reference to the Vestur-Isafjarsarsysla area. 
Doctoral thesis, Durham University.


The evolution of the landscape of Vestfir6ir, made almost entirely of volcanic rocks, is traced from the lilocene, when the oldest rocks formed, through the Pliocene and Pleistocene. Volcanic activity ceased first in the north western part leaving a basalt plateau with occasional large volcanoes protruding. Fluvial erosion, guided by a westerly dip of the plateau and tectonic lineaments, left a well developed drainage pattern there by the rime volcanic activity ceased in the southeast. The snowline fluctuated widely during the Plio-Pleistocene. Cirque and valley glaciations were very effective in sculpturing the landscape where the preglacial relief was greatest, in the northwest. Ice sheet glaciations affected the whole peninsula and offshore areas with linear erosion dominant in the northwest and areal scouring elsewhere. The glacial geomorphology of Dyrafjorour and northern Arnarfjorour is mapped. The highest marine limit is in the Nupur area, about 110 m, and shorelines and marine limits higher than 70 m are at 7 other localities at least. At least' two stages of glacial readvances are recognized: The Tjaldanes stage occurred when sea level was between 11 and 22 m and is probably of "Younger Dryas" age; later a readvance occurred in the cirques in the area. On the basis of evidence on cirque distribution, cirque elevation, zeolite zonation, distribution of glacial erosional landscapes, glacial history, marine limits, ice cap profiles and shelf moraine a model of maximum glaciations of Vestfir6ir is proposed: The whole of Vestfir6ir and the surrounding shelf areas was completely ice covered with no ice free areas. Such a stage of glaciation, the Latragrunn stage, probably prevailed in the Vestfirdir area during the last glaciation.

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