Náttúrufræðingurinn - 1985, Page 14

SUMMARY
Notes on the Geology
of the Eyjafjöll,
southern Iceland
by
Jón Jónsson
Nalional Energy Authority
Grensásvegi 9
108 Reykjavík
The Eyjafjöll mountain range is a volcanic
complex, perhaps best indicated as a central
volcano. The highest part is the active volcano
Eyjafjallajökull (1668 m) with its last eruption
in 1821-23. It is covered by a glacier. During
the years 1978-82 the author of this note has
spent few weeks working on a geological map of
the area, with an emphasis on geothermal activ-
ity and volcanism. It has been discovered that a
part of this complex is older than was previously
assumed and the rocks are reversely magne-
tized, which indicates an age of more than 0,7
million years. This means also that volcanic
activity has prcvailed here for more than
700.000 years. Basaltic andesites seem to be the
dominating rocks in that part of the mountain.
Ankaramitic lavas have been found in several
places. Tltey are usually in thick flows, por-
phyritic (plagioclase, augite and olivine) and
some of them containing up to 5 cm long crystals
of olivine.
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