The Botany of Iceland - 01.12.1914, Blaðsíða 14

198
THORODDSEN
rivers, so that no vegetation can thrive here. Below the soutliern
edge of Vatnajökull the farmsteads are therefore confined to oases
separated from one another by gravel-deserts and swollen glacier-
rivers. In many places the people have been obliged to move their
houses up on the mountain sides in order to avoid inundations
caused by the glacier-waters, and here the mountain-sides facing
south are covered with a luxuriant plant-growth, while the level
country below is devoid of vegetation. The sandy tracts liave
different names, such as Breiðamerkursandur, Skeiðarársandur,
Brunasandur, Mýrdalssandur, Sólheimasandur, etc. Of these the
largest is Skeiðarársandur (about 900 square km.), and taken to-
gether they cover an area of about 2700 square km. Between Ló-
magnupur and Mýrdalsjökull the lowland becomes broader and is
covered by extensive lava-íields, blown sand, gravel and volcanic
ashes, as large volcanoes occur in the neighhourhood. The largest
area of low land in Iceland lies between Eyjafjallajökull and the
peninsula of Beykjanes and is about 4000 square km. in extent; it
is hemmed in by tuff-mountains which in many places fall abruptiy
towards the plain. The lowest part of the lowland is only slightly
raised above sea-level, but it rises gradually towards the interior
where it ultimately branches off into different valleys; near Geysir
it reaches its greatest height above sea-level, about 150 metres. The
low land is not tlat everywhere, some parts of it are hilly, and a
few isolated mountains also rise from tlie plain. West of Hekla the
lowland, by means of a gentle rise, is in direct connection witli
the interior plateau, to the great danger of the inhabited districls, as
the blown sand, volcanic ashes and pumice dust which cover large
areas of the interior have thereby free access to the lowlands; there-
fore, in these regions, during north-westerly storms, large tracts of
grass-covered and inhabited land have been overwhelmed in the
course of time. The lowlands consist chiefly of grassland, and no-
where in Iceland do farmsteads occur so closely together as here,
these districts being well-suited to cattle-rearing. Three very well-
supplied rivers run through the lowland, viz. Markarfljót with a
large delta-land (Landeyjar), Thjórsá and Ölfusá, and besides these
there are many smaller ones. The eastern part east of Thjórsá is
called Bangárvallasýsla, the western Árnessýsla. At the head of Faxa-
flói there is another low area (about 1000 square km.) which on
an average has a height of only 20—30 metres. It is bounded bv
steep, basalt mountains which are arranged in a semicircle around