The Botany of Iceland - 01.12.1914, Page 64

248
THORODDSEN
eattle-rearing of the rural population. The peninsula of Reykjanes,
which is of no great elevation, more than half of its surface being
below 100 metres, and which has a comparatively mild climate
with a considerable rainfall, is, however, so poor in plant-life, that
only 4 per cent of the area is grass-covered. The area bounded
on the west by Lágaskarð and on the south by Hafnarfjörður is
about 1635 square km., but of this only at most 69 km. is occupied
by grassland. The greater part of the area of the peninsula of
Reykjanes is covered by more recent lava-streams, and has a scanty
vegetation; tlie inhabitants along the coast maintain themselves
chiefly by fishing.
As it has already been remarked, the surface of tlie lowlands
varies in character. It usually consists of loose masses, but some-
times also of solid rock wliich projects here and there through the
more recent formations and the older and more recent Iava-streams,
as crests, ridges and hills. As mentioned above, in South Iceland
large areas (2000-— 3000 square km.) are covered with glacial and
volcanic sand, through which branching glacier-rivers flow. Although
these sandy tracts originate mainly from river-gravel and sand, other
constituents are also found intermixed in tliem, for instance tuíf-dust,
and volcanic scoriæ and ashes, wliere active volcanoes occur in the
neighbourhood. On Mýrdalssandur volcanic slags and ashes pre-
dominate. River-gravel and glacial clay occur only upon the surface
of changing river-beds. The vast Skeiðarársandur, on the other hand,
is formed almost exclusively of rolled glacial-gravel mingled with
fine sand and clay, which increases in amount the nearer the coast
is approached. The various sandy tracts differ naturally somewhat
as regards the quality of the material and the size of the grains,
etc. Old lava-streams, also, extend over large areas of the lowlands;
they are usually covered with soil which supports a luxuriant vege-
tation with heather-moors, coppice-woods and grasslands. In thickly
inhabited districts such as Flói and Skeið, the substratum is of
lava, and in the former district it is marshy, as it lies so low (at
the level of the sea), that the water cannot drain off. FIói is jammed
in between two river-deltas so that the rain-water cannot be drained
away owing to the pressure of the bottom water, and in rainy
years this district suffers greatly from water which has no outlet,
so that the ground is quite boggy. The underlying lava protrudes
from every hill and the soil is mixed with lava-fragments. The low-
land tract of Flói gradually merges into the district of Skeið which