The Botany of Iceland - 01.12.1945, Síða 126

468
STEINDÖR STEINDORSSON
1. The Kringilsárrani Moraine.
The moraine is situated along the margin of Brúarjökull between
the rivers Jökulsá á Brú and Kringilsá, extending across the Krin-
gilsárrani mentioned repeatedly above. It was formed by the huge
Brúarjökull. This is often in motion, probably due to volcanic activity.
Sometimes it advances over a great distance, for instance in thc winter
of 1810, according to Thoroddsen, when the huge terminal
moraines were formed at the front of the glacier. In the course of time
these moraines were covered with vegetation, but in the winter of 1889-
1890 the glacier again showed a great activity, and in advancing swept
away the old terminal moraines and formed fresh ones where the ad-
vance of the glacier stopped. When Thoroddsen visited this re-
gion in the summer of 1894, the glacier front was situated quite close
to these fresh terminal moraines (Thoroddsen, Ferð. III, pp. 279-
281). When I visited the region in 1933, a great change had taken
place. The glacier front had receded so much that the distance from
the glacier to the terminal moraine was c. 5 km. The moraine forms
a high and thick ridge across Kringilsárrani called Hraukar. Below the
ridge, there occurs a melar rather poor in vegetation, which bears
distinct traces of having been flooded by the glacier streams. The
morainic ridge itself is mostly covered by a luxuriant vegetation. Large
parts of the ground moraine, also, support some vegetation, which is
closest nearest the terminal moraine, but still open everywhere, the
plants occurring in small cushions or tufts. The whole ground moraine
has a very uneven surface with numerous clay and gravel hillocks, most
of them elongated and narrow and probably still containing a nucleus
of ice. In the depressions between these hills, pools often occur, especial-
ly in old beds of rivers or brooks. Otherwise the vegetation is chiefly
found in the depressions, the hills being, as a rule, quite bare. Nearest
the glacier there is a belt some hundred metres broad which is entirely
devoid of vegetation. Of the species growing nearest this belt Arabis
alpina, Draba rupestris, and Catabrosa algida are the commonest; rarer
are Deschampsia alpina, Poa alpina, and Cerastium trigynum.
(Table XXIII. A-B).
As mentioned above, it is only well over forty years since this
moraine was entirely covered with ice, which is shown by T h o r o d d-
s e n’s description. It seems not unreasonable to assume that the vegeta-
tion did not begin to establish itself there till about ten years after the