The Botany of Iceland - 01.12.1914, Page 40

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THOIíODDSEN
sheep’s skins, and the hoofs of the sheep turned yellow when they
walked amongst them; while therainwhich fell from the dust-clouds,
is said to have been so sharp and biting that it was painful where
it fell on the hands and face. The volcanic eruptions, on the wliole,
have had a very injurious influence upon the plant-distribution
in the volcanic regions of Iceland. During the eruptions a great
number of sheep and cattle die from want of food or from its un-
wholesome nature, and of various diseases caused by the ashes eaten
with the fodder. No eruption has however been so disastrous as
the eruption of the Laki crater-rows in 1783. In the winter which
followed, and in the spring of 1784, the sheep and catlle suffered
from all kinds of diseases owing to the unwholesome food, and
died by scores. On many farmsteads the entire live-stock died out,
and the following year there died in the whole of Iceland 11,500
cattle, 28,000 ponies and 190,500 sheep — about 53 per cent of all
the cattle, 77 per cent of the ponies and 82 per cent of the sheep.
Then came a famine, which carried oíf 9500 of the inhabitants,
about one-flfth of the total population of Iceland at that time.
In Iceland there are several types of volcanoes. Usually, by a
volcano is understood a large hill or mountain, more or less conical
in form, which is ignivomous, discharging lava-streams and ejecting
ashes and fragments of lava. Volcanoes of this description occur
in Iceland, but are not common; seven or eight such volcanic moun-
tains are known, which resemble externally the well-known Italian
volcanoes of Vesuvius and Etna, without however being so regular
in form; they are built up of alternating layers of ashes, lava and
slag, and usually resemble truncated cones with a crater at the
top, and a considerable angle of inclination (at tlie base 8°—15°;
at the top 20°—35°); the majority of them have their summits
covered with snow and glaciers. Of these volcanoes the largest and
best knowm are Öræfajökull, Snæfellsjökull and Eyjafjallajökull.
Hekla is also built up of alternating layers of lava and tuff, but is
not conical. Its shape conforms to an elliptical ridge, rent down
its major axis, and studded with a row of craters along the line of
fissure. Another type of Icelandic volcano are tlie dome-shaped
“lava-cones” (dyntjja, pl. dijngjur) — larger or smaller volcanoes,
built up entirely of Iava-streams, without any intermediate lavers
of tuff or slag. Volcanoes of this description, which are also found
in the Sandwich Islands, are distinguishable from the country sur-
rounding them as shield-shaped cones, and their altitude is low