Greinar (Vísindafélag Íslendinga) - 01.01.1967, Page 42

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origin of other islands in the group lying along a NE-SW
tectonic fissure, which is a part of the Atlantic ridge.
Remnants of volcanic craters are noticeable throughout
the islands, which are mostly made of palagonite tuff
(consolidated volcanic ash) with streaks and veins of in-
truded basalt. The palagonite tuff accounts for most of
the bedrock, but large areas of Heimaey and Surtsey are
also covered with lava. These two are the largest islands,
and they show greater variation in topography than the
smaller members of the group, some of which are mere
stacks, 50 m high with a mantle of vegetation on the
slanting summit. The soil in the older islands is rather
deep, loessy in character, fertile and rich in organic mat-
ter due to bird-droppings. Sea birds inhabit the islands
in great numbers; among these is the puffin (Fratercula
arctica) which digs deep nesting holes in the soil on the
top of the islands whereas the other bird species inhabit
the cliffs.
Climate
No meteorological records have been carried out on
Surtsey or the smaller islands. On Heimaey, however,
there is a meteorological station with available records
from 1872.
The climate is highly oceanic. It is relatively warm and
moist in comparison with the average climate on the main-
land or, for example the island of Grímsey off the north-
ern coast of Iceland. The precipitation is the seventh
highest, and the mean temperature the third highest in
Iceland (Table I).
Excursions
The study was performed during the summers of 1965
and 1966. Various excursions were made to the smaller is-
lands from Heimaey, which was used as a base of opera-
tions. The study commenced in early July 1965 when the
students, Björn Johnsen and Sigurdur Helgason went to