Náttúrufræðingurinn - 1966, Blaðsíða 63

NÁTTÚRUFRÆÐINGURINN
209
Einarsson, Þorleifur, 1965. GosiS í Surtsey. Reykjavík.
Stefánsson, Unnstpinn, 1966. Influene of the Surtsey Eruption on the Nutrient
Content of the Surrounding Seawater. Verður birt í Journal of Marine
Research.
Surtseyjarnefnd, 1965. Surtsey Research Progress Report, I., Reykjavík.
Thorarinsson, Sigurður og Vonnegut, Bernard, 1964. Whirlwinds Produced
by the Eruption of Surtsey Volcano. Bull. Am. Met. Soc. Vol. 45, No. 8,
bls. 440—444.
SUMMARY
Geophysical research in connection witli the volcanic eruption at Surtsey
by Thorbjorn Sigurgeirsson,
University of Iceland.
The present paper is a survey of geophysics research carried out in connec-
tion witli the volcanic eruption at Surtsey, off the south coast of Iceland. This
work was carried out by many scientists, both from tliis country and front abroad,
in the years 1963—1965. Progress reports on this work are published in English
by the Surtsey Research Society, Reykjavík, Iceland.
The heat output in the early stages of the eruption has been estimated about
100 million kilowatts (Thorarinsson and Vonnegut 1964). Before the visible
eruption some rise of temperature was found in the sea, but no appreciable
heating occurred after the eruption reached the surface of the sea. It is con-
duded that then only a small fraction of the heat output entered the sea, and
that most of it went diretly into the atmospliere.
The most striking influence of the eruption on the sea was an increase in dis-
solved silica which, during the early phases of the eruption, could be detected
out to að distance of 10—20 km (Steíansson 1966).
Observations of glowin lumps of lava tlirown 2000 m up in the air indicate
an initial velocity of about 200 m/sec, and the complete absence of detonations
shows that ejection velocities were subsonic throughout the eruption. Time-
lapse photographs taken in Reykjavík, 114 km from the volcano, during tlie
first two weeks of the eruption give a general idea of the behaviour of the
volcanic cloud above 3,3 krn altitude. New clouds rise with a velocity which
often amounts to 10—20 m/sec. Usually the top of the cloud is 6—8 km above
sealevel, and the maximum lieight observecl on tliese photographs is 9,2 km.
Fig. 1 shows the height of the volcanic cloud as it varies with time on
December lst, 1963.
Lightenings were frequently observecl froni Vestmannaeyjar and occasionally
from Reykjavik during the explosive phase of the eruption. Electric field mea-
surements made from a boat and in a plane showed primarily a positive charge
in tlie volcanic cloud, and a positive charge was also found in the cloud whicli