Jökull - 01.12.1972, Blaðsíða 66

work was supplemented, at the suggestion of
Professor Sigurður Thorarinsson, by a survey
of Falljökull. In 1967 the work was supervised
by Bob Metcalfe (Bristol Grammar School) who
is a trained surveyor and has spent two years
in Antarctica in that capacity. The party sur-
veyed Virkisjökull, the southern arm. In 1968
the map was completed by a party led by Tony
Escritt (Harrow School) although rnost of the
work was undertaken by Lisle Ryder (Selwyn
College, Cambridge). In both years the mor-
aines were mapped by parties of unskilled boys
supervised by Peter Macklin (formerly of Dur-
ham University).
The glacier was mapped at a scale of 1:10,000
using a theodolite and plane table equipment.
Substantial cairns were built wherever firm
ground was available. Elsewhere flags or yellow
paint was used. These points should be easily
retrieved but in case of doubt they are docu-
mented and filed at the Brathay Field Study
Centre. The height control was based upon the
yellow datum post west of the Virkisjökull
snout whose height “had been tentatively fixed
by aneroid barometer at 300'” (R. J. M. 1967).
Once established the lteight of the ice base
line w'as fixed by theodolite, other heights by
clinometer. It is to be regretted that the metric
system was not used in the initial mapping.
Inspection of the tabulated clinometer read-
ings shows that only in two or three cases is
there a discrepancy of more than 10' between
readings and in most cases rather less. By and
large the satisfactory nature of the clinometer
heights would seem to endorse the reliability
of the horizontal control on the plane table.
Intersections were satisfactory except in the
case of two summits to the North of the glacier
— 2460' and 3133' — which were included at
the end to assist in the drawing of the con-
tours. Perhaps a suitable margin of error to
allow in horizontal control would be 15' or 20'
on the lower end and central parts of the
glacier extending to 50' or so at the icefall.
The contours established in 1968 agreed very
closely witli those of the 1967 survey and fre-
quent checks with the control at all stages
showed the reliability of tlie maps to well up
the icefall. Distinction has been made between
ice, moraine and ice-cored moraine. In many
cases this was difficult to determine but the
contours may be taken as a reasonably reliable
representation of the situation in 1967/68. The
contours of the ice-cored moraine are necessari-
ly generalised. Doubt also arises as to the ac-
curacy of the lowest moraines due West of the
two snouts; most of the boys surveying there
were taking the responsibility for the first time.
The outwash streams have not been mapped
in every detail since they change their courses
so rapidly. In 1967 the course of a stream was
mapped from the snout of Virkisjökull west-
ward to the main outwash valley, This stream
now disappears down a set of swallow holes in
ice-cored moraine about 200 yards clownstream
of the snout at a point where, in 1967, ice-
cored moraine was thought not to exist. The
map has been adjusted. After heavy rain how-
ever the valley is fully occupied.
A more detailed report has been lodged with
Jöklarannsóknafélag Islands and fuller details
are available from the author.
ÁGRIP
KORT AF FALLJÖKLI í ÖRÆFUM
I Vatnahéraði i norðvesturhluta Englands
hefur siðan 1947 starfað félagsskapur, er nefn-
ist Brathay Exploration Group, kenndur við
Brathay Hall, sem er megin aðsetur þessa félags-
skapar, og vceri þeim, er sinna, ceskulýðsstarfi
hérlendis, vissulega fengur í að kynnast þvi
ágceta starfi, sem þar er unnið.
Þar eru árlega haldin sumarnámskeið fyrir
unglinga og einnig skiþuleggur þessi félagsskap-
ur frceðslu- og rannsóknaferðir til ýmissa svceða,
innan og uta,n Bretlands, þar sem unglingar
eru þjálfaðir í ýmsum náttúrufrœðilegum rann-
sóknum undir stjórn fcerra manna.
Fyrsta Brathay-ferðin til íslands var gerð árið
1953 og hafa síðan verið gerðar margar slikar
hingað, einkum til Örcefa, m. a. i því skyni að
rannsaka skúma á Breiðamerkursandi. Sumur-
in 1967 og 1968 vann nokkuð a,f leiðangurs-
mönnum að þvi að gera kort af Falljökli, og er
það kort birt hér, ásamt greinargerð um korta-
gerðina og lýsingu á jöklinum, eftir E. A. Esc-
ritt. Kortið er gert i mcelikva,rða 1:10.000 og
eru hceðir í fetum að brezkum sið, en hceðar-
línur með 50 feta hceðarmun. S. Þ.
64 JÖKULL 22. ÁR