Jökull - 01.12.1984, Page 28

Fig. 1. SW-Vatnajökull,
Skeidarársandur and
rivers that drain Vatna-
jökull.
1 .myncL. Suðvesturhluti
Vatnajökuls, Skeiðarár-
sandur og ár sem falla frá
Vatnajökli.
the triggering of jökulhlaups, estimates of the
total output of heat from the geothermal system
and the mechanism of heat extraction, the chemi-
cal composition of the water in the jökulhlaups
and the possibilities of predicting the floods by
chemical monitoring of river water. This paper
adds new information about the geothermal
activity and recent volcanic events, the heat flux
transported by the geothermal fluid and the
triggering mechanism of jökulhlaups. The work is
based on various field studies but most of the
information is gained from geochemical studies in
the Grímsvötn area and from chemical studies of
water in jökulhlaups.
Field studies in the Grímsvötn area date back
to the year 1919 (Wadell 1920). The next studies
in the area were done by expeditions during the
volcanic eruption in 1934. (Einarsson 1946,
Áskelsson 1936, Nielsen 1937 ). During the
jökulhlaup in 1938 the area was studied from the
air. Thorarinsson and Sigurdsson (1947) summa-
rize all expeditions to the area from 1934 to 1947.
Later expeditions are described by Thorarinsson
(1953a, 1953b, 1954, 1955, 1956, 1957, 1958,
1965, 1974), Eythorsson (1957,1960), Áskelsson
(1959), and Björnsson (1974, 1977). Recent
observations of the Grímsvötn area have been
carried out in the annual expeditions of the Ice-
land Glaciological Society, in which the Science
Institute and the National Energy Authority
(NEA) have participated.
Thorarinsson (1974) has compiled a history of
26 JÖKULL 34. ÁR