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gion du Kjölur sur le plateau central de l’Islande. Revue de Geo-
morphologie dynamique. No 1: 23-39. Paris.
— 1966b: Stapakenningin og Surtsey (A comparison of tablemountains
in Iceland and the volcanic island of Surtsey off the south coast of
Iceland). Náttúrufræðingurinn 3d/ 1-34.
Mathews, W. H., 1947: “Tuyas”. Flat-topped volcanoes in northern Bri-
tish Columbia. Am. Jour. Sc. 245: 560-570.
Sigurgeirsson, Th., 1966: Geophysical measurements in Surtsey carried out
during the year of 1965. In: Surtsey Research Progress Report, II,
181-185.
Thorarinsson, Sigurdur, 1965: The median zone of Iceland. In: The World
Rift System. Geol. Survey of Canada, Paper 66-14: 187-211.
DISCUSSION
S. A. Malmberg: On November 13, 1963, a day before the
visible eruption in Surtsey, a ship conducting herring search
in the coastal area south of Iceland (M/T Thorsteinn Thorska-
bítur) recorded a distinct surface temperature maximum of
9.4°C about 2 miles southwest from the present Surtsey,
while the temperature in other parts of the region was about
7°C. This temperature maximum can only be explained by
underwater volcanic activity.
Trausti Einarsson: Although pillow lavas are found in the
lower parts of some móberg mountains I would not consider
it certain that they are as a rule formed at the beginning of
a submarine eruption. The critical pressure of vapour is 205
kg/cm2, which corresponds to a depth of 2000 m in water.
At a shallower depth than 2000 m the vapour that is pro-
duced by contact of magma and water should be able to ex-
pand and play havoc with the magma. Fine glass shards,
formed in the process, might spread with currents, but most
of the material would probably be piled up locally, although
not necessarily in the form of pillows.
5. A. Malmberg: On August 2, 1966, beam transmittance
measurements were carried out in the area around Surtsey
and Jólnir, from the surface to the sea bottom. The measure-
ments were made on 14 stations all around the islands, in a
distance from 150 m to 12 miles from the islands. No vol-