Náttúrufræðingurinn

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Náttúrufræðingurinn - 01.02.1966, Blaðsíða 31

Náttúrufræðingurinn - 01.02.1966, Blaðsíða 31
NATTURUFRÆÐINGURINN 209 Einarsson, Þorleifur, 1965. Gosið í Surtsey. Reykjavík. Stefánsson, Unnstfinn, 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, L, Reykjavík. Thorarinsson, Sigurður og Vonnegul, 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 with 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 with the volcanic eruption at Surtsey, off the south coast of Iceland. This work was carried out by many scientists, both from this country and from 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 atmosphere. 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 (Stefansson 1966). Observations of glowin lumps of lava thrown 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 the first two weeks of the eruption give a general idea of the behaviour of the volcanic cloud above 3,3 km 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 height observed on these 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 observed from 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 the volcanic cloud, and a positive charge was also found in the cloud which

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