The Botany of Iceland - 01.12.1914, Blaðsíða 36

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THORODDSEN
jökull, and extends down to the south coast near Eyrarbakki, covers
an area of 1550 square km. In the low land this lava-field is
covered by a thick layer of soil upon which dense settlements have
arisen. In addition, extensive lava-fields (1530 square km.), which
originated from 28 volcanoes, occur on Reykjanes; and upon the
plateau on either side of Langjökull, there are also other Iarge lava-
íields (1030 square km.) of which Hallmundarhraun is the best
known; in it is the lava-cavern, Surtshellir, which is H/a km. in
Fig. 7. I.ava-stream (apalhraun); upon the outer south-west slope of Dyngjufjöll.
(Pliot. Heinrich Erkes.)
length. Large tracts of lava occur also around Hekla, near Mývatn,
Kelduhverfi and in several other places.
The surface of the lava-streams varies greatly; often it is very
rugged and jagged and is then, in Iceland, called apalhraun, and
in the Sandwich Islands, aa. Such slreams consist exclusively of
porous and brittle Iava and slaggv fragments heaped together pell-
mell. Such lava-streams are comparatively narrow, with high edges
which, seen from a distance, look like fences or ridges upon the
level land. A lava-stream of this description is very difticult to cross,
owing to the fragments being put together so Ioosely that tliey are
disturbed by the slightest touch. Other lava-fields, especially the