Jökull - 01.12.1972, Side 40

associated solfataras described by Thorarinsson;
in 1968 it was of greater magnitude than ap-
parent in 1966, and 2) north--northeast of
Jökullón, roughly coincident with Gámur, ancl
located within the area of highest thermal
emission shown on the 1966 infrared imagery.
Major lce Cauldron
Southeast of Jökullón and the new steam
vent of 1968 is a major ice cauldron subsidence
structure (Fig. 8) sketched earlier by Thorar-
insson (1953, p. 29, Fig. 11). In the spring or
early summer of 1959, explosive activity oc-
currecl within the cauldron (Jóhannsson 1959).
The 1966 imagerv shows several points of
thermal emission around its inner walls, parti-
cularly on its west and north sides (Fig. 4).
The cauldron floor appears ice-covered and
cold, but a semiconcentric pattern of crevasses
appearing in light tones on the infrared image
arouncl the ice cauldron probably indicates
thermal convection along the crevasse surfaces
(Fig. 5). The photographs and infrared images
indicate the crevasse pattern extended for
more than a kilometer to tlie southwest.
The 1968 infrared imagery suggests that
radiation from the cauldron diminished be-
tween 1966 and 1968 (Fig. 6). Thermal emis-
sion from the west rim appears to have de-
clined and several smaller points of emission
on the north rim have disappearecl entirely.
The dimensions of the cauldron proper, as
measurecl on 1968 Infrared Ektachrome and
Plus X photographs are 620 meters southwest-
northeast and 590 meters northwest-southeast
(Fig. 8). The area of the cauldron floor is
about 0.37 km2. If the area beneath the caul-
dron subsidence fractures is included, the total
V
x
\\
lce cauldron

Amphitheater and largest
S
Kverkf jöll
Glacier

Fig. 8. Part of thermal area in Kverkfjöll vestri in August 1968, interpretecl from Plus X and
Infrared Ektachrome aerial photographs.
Mynd 8. Hluti jarðhitasvœðisins i Kverkfjöllum vestri samkvcemt túlkun á Plus X og innrauð-
um Ektachrome myndum, sem teknar voru í ágúst 1968.
38 JÖKULL 22. ÁR