The Botany of Iceland - 01.12.1914, Blaðsíða 10

194
THOROD0SEN
Vatnajökull cover an area of about 8000 square km. The axis of
elevation lies from NW. to SE., from somewhere near the head of
Hvammsfjörður to Hornaljörður; it does not, however, consist of
one continuous ridge, but of a series of snow-covered, dome-shaped
mountains separated by broad stretches of more level ground. These
snow- and ice-covered domes are strictly speaking a series of small
plateaus which rise from the main plateau to an absolute height
of 1400-2000 metres, as compared with 600—1000 metres above
the plateau. The most easterly of the great glacier-bearing moun-
tains is Vatnajökull which is separated froin the much smaller
Tungnafellsjökull (100 square km.) by Vonarskarð (1000 metres); be-
tween Tungnafellsjökull and Hofsjökull (1350 square km.) lies the
broad stretch of level ground, Sprengisander (650 metres); west of
Hofsjökull and between the latter and Langjökull (1300 square km.)
lies Kjölur or Kjalvegur (600 metres); and between Langjökull and
Eiriksjökull (100 square km.), Flosaskarð (800 metres). The plateau
north of the last-mentioned ice-mountains abound in lakes and bogs.
The interior plateau consists chiefly of deserts almost destitute of
vegetation, but the surface varies somewhat in character in accord-,
ance with the geological nature of the underlying rock. Where
basalt or dolerite forrns the substratum, the surface is strewn with
innumerable angular blocks of rock, split asunder bv the action of
frost; where tuff and breccia form the foundation, the surface is
usually covered with gravel and fragments of slaggy lava which
have been loosened from the breccia by the action of weathering.
More than one-half of the plateau is overlain by more recent
formations — lava, blown sand, volcanic ashes, glacial forma-
tions, clay and river-gravel. The lava-flelds, taken together, cover
a very large area in the interior and present a most desolate
scene; as far as the eye can reach only a black, hardened mass is
seen, and the dark colours are only here and there interrupted by
mounds of reddish slag, smoking craters, scattered snow-drifts, and
in the distance by glistening, white Jökull-domes; there is no sign
of Iife and an oppressive silence reigns over the land.
The interior plateau is trenched by many valleys, chiefly towards
the north and east; between these valleys long mountain spurs —
the skeletal ribs of the eroded plateau — branch outwards toward
the sea. Of these, the mountain-mass which exten'ds towards the
south, and is crowned at the top by Myrdalsjökull, is the most
considerable. Towards the west the two volcanic mountain-chains