Jökull - 01.12.1964, Síða 3

JÖKULL
A R S R I T
J Ö KLARAN NSÓ KN AFÉLAGS ÍSLANDS
III
14, ÁR REYKJAVÍK 1964
Gravity Measurements in the Grímsvötn Area
BY
GUDMUNDUR PÁLMASON
(STATE ELECTRICITY AUTHORITY, REYKJAVÍK)
SUMMARY
Results of gravity-measurements in the Grims-
vötn area on the Vatnajökull ice sheet are
given. A small area around Grímsvötn and a
line Grimsfjall—Kverkfjöll were surveyed, and
a connection was made with the Icelandic net
of gravity statiohs: Estimate of ice-thickness are
made as well as a comparison with ávailahle
seismic thickness-determinations.
INTRODUCTION
On two of the expeditions of the Icelandic
Glaciological Society to Vatnajökull in 1960 and
1961 sorne gravity measurements were made,
mainly in the Grímsvötn area. The aim of
these measurements was twofold; firstly to make
a survey of a limited area around Grímsvötn,
mainly for the purpose of inferring subglacial
topography, and secondly to establish a connec-
tion between that area and the net of gravity
stations in Iceland. On the first expedition in
1960 the measurements were made by the
author, while on the second, in 1961, they were
made by Mr. Orn Garðarsson. The present
report gives the results of these measurements.
JÖKULL 1964
THE MEASUREMENTS
The gravity work here described was made
possible by the geodetic levellings, whicli were
being carried out on the above two expeditions
in the Grímsvötn area. On the first expedition
in 1960 gravity readings were taken at 45 sta-
tions over an area of 70 km2 within and east of
the Grímsvötn depression, and a gravity station
at Grímsfjall was connected with the gravity
station at the University of Iceland in Reykja-
vík. On the seconcl expedition in 1961 gravity
readings were taken along a profile frorn
Grímsfjall towards Kverkfjöll, which was being
levelled, and along a short profile perpendi-
cular to it, but no connection was made with
the gravity station in Reykjavík.
The location of the area around Grímsvötn,
and the profile Grímsfjall—Kverkfjöll, is shown
in Fig. 1.
The location of the gravity stations in the
Grímsvötn depression and northeast of it was
determined by geodetic methods, but the sta-
tions to the east and southeast were determined
using the distance meter of a weasel, a com-
pass, and a Paulin altimeter. These latter
stations were measured on one closed loop
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ÍSLANDS