The Botany of Iceland - 01.12.1914, Page 17

PHYSICAL GEOGRAPHY
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through their glaciers and glacier-rivers they exert a great intluence
upon the surface and climate of the country and upon the condi-
tions of life of the inhabitants. The Icelandic climate is specially
adapted to the development of large glaciers, for the air is raw and
cold and inoist, tlie amount of rainfall consideraiile and the summer-
heat slight. The amount of precipitation is greatest towards the
south-east and there the interior table-land is covered by the great
Vatnajökull. The altitude of the snow-line varies from 400 to 1400
metres in the dilTerent parts of the country, and the level ahove
the sea at which the glaciers end differs greatly; in the north on
the north-western peninsula, and in the south near Vatnajökull, the
glaciers descend almost to the sea, to 25 metres and 9 metres above
sea-level respectively at the lowest points to which thev descend.
The great ice-mountains of Iceland are without exception closelv
associated with the plateau. Large areas of the highest part of the
plateau are covered with névé ■ which occurs as slightly-arching
domes or undulating snow-fields of great thickness. Prominent
mountain-peaks are rare; the latter do not appear until near the
edges of the snow-fields and usually as outstanding summits of the
underlying rock. The surface of these snow-fields is devoid of
gravel; this does not appear until it does so at the extremities of
the glaciers which are often quite black with it and with sand and
blocks of rock. The large glaciers which descend from these névé-
covered flats have, on an average, a very slight declivity; only in
places where precipitous mountain-peaks project from the edge of
the snow-field, do steep glaciers of small dimensions occur. The
large glaciers of Iceland closely resemhle the glaciers typical of
Arctic countries; but there are a great many small glaciers which
resemble those of the Alps. Several of the broad glaciers which
descend from Vatnajökull cover a very considerable area (e. g. Dyngju-
jökull 400 square km., Bruarjökull 500 square km., etc.). Peculiar
to Iceland are the so-called “glacier-lorrents” (Jökul-hlaup). When
the glaciers, by the eruption of volcanoes hidden under the ice, are
broken to pieces and melt, the large stretches of land beneath them
are inundated by a roaring sea of dirty water with swirling ice-
bergs. Such catastrophes may cause great changes in the surface-
features of the surrounding country, as the waterfloods often carry
along with them an incredible quantity of gravel and rocky blocks.
In this way the volcano of Katla especialljr has caused considerable
changes — the course of rivers are constantly changed, the smaller