Jökull - 01.12.1953, Side 33

reasonable bounds but the work has had to be
postponed for work in Greenland. It is intended
to continue some of the investigations in Green-
land but the main theme of the Iceland work
— the rock debris on ice — has had to be re-
placed in Greenland by the theme of regime
since there is less debris present in N. E. Green-
land and the glaciers may be geophysically classi-
fied as ”arctic” instead of „temperate” as in
Iceland (Ahlmann 1948).
The observations in Iceland require further
analysis and calculation as outlined in the sect-
ion on the heat balance at the ice surface. The
correlation of the summer ablation records taken
in Iceland since 1948 should make a most useful
report on ablation, the factors causing it and
the deposition resulting from it. The first ana-
lysis of the ablation processes and of the surface
morphology relevant to rock debris is presented
here with an outline of the method of further
analysis proposed to achieve a better correla-
tion of quantitative and qualitative results. A
summary of this first analysis may be outlined:
1. Ablation in Iceland due to conduction,
advection and radiation in that order of
importance.
2. The rate of ablation of a clean ice surface
is highest in rain following sunshine.
3. The rate of differential ablation which
causes the growth of dirt cones, moraines
and dirt band projections, etc., is greatest
during periods of sunshine following rain.
4. Bottom melting, where measurable, is grea-
ter than surface melting.
5. Rock debris is concentrated on a glacier at
the surface of the snout and secondly at
moraines and dirt cones. The rock debris
present is largely localised at these surface
forms.
6. The amount of englacial debris as a per-
centage of the total volume is very small
indeed and increases slightly from the
surface downwards. At the surface it aver-
ages 0.1% by weight for clear ice and 1.1%
for ice under a burden of supra glacial
debris.
REFERENCES:
Ahlmann, H. W., 1937. Vatnajökull. The Abla-
tion. — Geogr. Ann.
Ahlmann, H. W., 1947. Glacial Observations
round the N. Atlantic Coasts. — R. G. S.
Research Series No. 1.
Ágstrom, A., 1937. Radiation Measurements in
Spitsbergen. — Geogr. Ann.
Bagnold, R. A., 1938. The Physics of Blown
Sand and Desert Dunes. — London.
Barnes, H. T., 1928. Ice Engineering. — Mon-
treal.
Carruthers, R. G., 1943. The Secret of Glacial
Drift. — Part I Proc. Yks. Geol. Soc.
Flint, R. F., 1947. Glacial Geology and The
Pleistocene Epoch — (p. 74) — New York.
Geiger, 1950. Micro Climate. — London.
Gorzynski, 1933. Measurement of Radiation
from Sun and Sky.
Kaye, G. W. C., and Laly, T. H„ 1948. Physical
and Chemical Constants. — London (p. 30).
Lewis W. V., 1497. Dirt Cones on the N. Margin
of Vatnajökull. — Journ. of Geomorph.
Middleton, W. E. K„ 1935. Meteorological In-
struments. — Toronto.
Pasquill, F„ 1949. An Apparatus for the study
of temperature and humidity near the ground.
— Qu. Journ. Roy. Met. Soc.
Pasquill, F„ 1950. Evaporation from an Agricul-
tural Land Surface. — Proc. Roy. Soc. A.
Sharp, R. P„ 1948. Studies of Super Glacial de-
bris in the Mt. St. Elias Range. — Am. Journ.
Science.
Shepherd, 1949. A sensitive anemometer for low
wind speeds. — Jour. Sci. Insts.
Swithinbank, C„ 1949. Dirt Cones and their for-
mation. — Jour. of Glaciology.
Sverdrup, O., 1935. — Met. Measurements on
Isachsen’s Plateau. — Geogr. Ann.
Wallen, C. C. 1948. Glacial Met. Studies in
Swedish Lappland. — Geogr. Ann.
„RÚSTIR“ KOMA OG HVERFA.
Daníel Þorleifsson bóndi á Stóra-Búrfelli A.-
Hún. segir rústir hafi verið horfnar að mestu úr
flám á Kúluheiði eftir 1940, þ. á m. fyrir ofan
Sólheima (á Svínavatnshálsi), í Guðlaugsstaða-
flánni, Kolkuflóa og Kúlukvíslarflóa. — En sum-
arið 1951 fór að bera á rústamyndunum aftur
vegna frosta og vorkulda „en rústirnar koma af
klaka í jörðinni", sagði Daníel. Sumarið 1951
var víða klaki í uppmokstri eftir skurðgröfur o.
s. frv.
(Eftir viðtali 8. nóv. 1953.)
/• Ey.
31