Jökull - 01.12.1989, Blaðsíða 19
have been substantial. It is suggested that the
observed drop in heat flux from the area in recent
years can be explained by the decrease in vol-
canic activity since 1940. The heat stored in lava
flows and shallow intrusions is now exhausted.
ACKNOWLEDGEMENTS
The project was supported by a grant from the
Icelandic Science Fund. The National Energy
Authority (Orkustofnun) and The Science Institute
(Raunvísindastofnun), University of Iceland gave
valuable support in supplying manpower and equip-
ment while out in the field. Especially the author is
indebted to Jósef Hólmjám, Orkustofnun, for his
participation and Dr. Helgi Björnsson for his con-
tinuing support. The Icelandic Public Road
Administration supplied explosives. The author
acknowledges the receipt of a Foreign and Com-
monwealth Office Scholarship (FCO) and an Over-
seas Research Student Scholarship (ORS) while
studying at UCL. The author would like to thank his
supervisor, Dr. John Milsom, for his support as well
as critical and constructive comments on drafts of
this paper. Professor Sveinbjörn Björnsson, Karl
Gunnarsson and Dr. Ólafur Flóvenz read the
manuscript and suggested several improvements of
the paper.
REFERENCES
Áskelsson, Jóhannes. 1934. Síðasta eldgosið í
Vatnajökli (in Icelandic). Náttúrufrœðingurinn 4,
61-74.
— 1936. On the last eruptions in Vatnajökull. Soc.
Sci. Isl. 18, Reykjavík, 68 pp.
Bjömsson, Helgi. 1974. Explanation of jökulhlaups
from Grímsvötn, Vatnajökull, Iceland. Jökull 24,
1-26.
— 1983. A natural calorimeter at Grímsvötn; an
indicator of geothermal and volcanic activity.
Jökull 33, 13-18.
— 1986. Surface and bedrock topography of ice
caps in Iceland mapped by radio-echo soundings.
Annals ofGlaciology 8, 11-18.
— 1988. Hydrology of ice caps in volcanic
regions. Soc. Sci. Isl. 45, Reykjavík, 139 pp.
Bjömsson, Helgi and Hrefna Kristmannsdóttir.
1984. The Grímsvötn geothermal area, Vatnajök-
ull, Iceland. Jökull 34, 25-50.
Bjömsson, Helgi, Sveinbjöm Bjömsson and Þor-
bjöm Sigurgeirsson. 1982. Penetration of water
into hot rock boundaries of magma at Grímsvötn.
Nature 295, 580-581.
Bjömsson, Sveinbjörn. 1987. Kólnun Eldfellshrauns
og nýting hraunhita (in Icelandic). In: Sigfús-
son, Þ.I. ed. I hlutarins eðli, Menningarsjóður,
Reykjavík, 301-321.
Brandsdóttir, Bryndís. 1984. Seismic activity in
Vatnajökull 1900-1982 with special reference to
Skeiðarárhlaups, Skaftárhlaups and Vatnajökull
eruptions. Jökull 34, 141-150.
Buntebarth, G. 1980. Geothermie. Springer-Verlag,
Berlin, 156 pp.
Cermák, V. and L. Rybach. 1982. Thermal conduc-
tivity and specific heat of minerals and rocks. In:
Angenheister, G. ed. Landolt-Bömstein, Vol. 1,
Physical properties of rocks, Subvolume a.
Springer-Verlag, Berlin, 305-343.
Dix, C.H. 1955. Seismic velocities from surface
measurements. Geophysics 20, 68-86.
Einarsson, Páll and Bryndís Brandsdóttir. 1984.
Seismic activity preceding and during the 1983
volcanic eruption in Grímsvötn, Iceland. Jökull
34, 13-23.
Eyþórsson, Jón. 1951. Þykkt Vatnajökuls (in Ice-
landic). Jökull 1, 1-6.
Eyþórsson, Jón. 1952. Landið undir Vatnajökli (in
Icelandic). Jökull 2, 1-4.
Grant, F.S. and G.F. West. 1965. Interpretation
theory in applied geophysics. McGraw Hill, New
York, 584 pp.
Grönvold, Karl and Haukur Jóhannesson. 1984.
Eruption in Grímsvötn 1983: course of events
and chemical studies of the tephra. Jökull 34, 1-
11.
Joset, A. and J.J. Holtzscherer. 1953. Etude des
vitesses de propagation des ondes seismiques sur
Tinlandsis du Groenland. Annales Geophysique 9,
330-344.
— 1954. Expedition Franco- Islandaise au Vatna-
jökull mars-avril 1951. Resultats des sondages
JÖKULL, No. 39, 1989 17