Jökull - 01.12.1976, Blaðsíða 9

Mynd 5. Jarðmyndanir ofan við Lund.
It has been suggested previously that changes
in base level may have accounted for some of
the features found on Tungufellsflói. From the
evidence of floating ice provided by the ‘deigul-
mór’ at Lundur it seems probable that late-
glacial changes in sea-level hay have been the
controlling factor in base-level changes. It is
probable that there are two such critical levels,
first, the level of the sea surface and second,
the level of the base of the floating ice shelf.
Movement of water inside the ice shelf and its
adjacent land ice is probably controlled by the
sea surface level (Röthlisberger, 1972, p. 187)
but deposits under the ice shelf cannot rise
above the level of its base. Quite thin deposits
of deigulmór, therefore, may be the result of a
high sea-level in which thick ice floats with its
base only a few metres above the rock floor,
especially in the high valley like Lundarreykja-
dalur.
REFEREN CES
Ashwell, Ian Y. 1965. The Hestháls glacial
drainage channels. Jökull 15: 129—134.
— 1975. Glacial and late-Glacial processes in
Western Iceland. Geogr. Annlr. 57A: 225—
245.
Einarsson, Trausti. 1958. Landslag á Skagafjall-
garði, myndun þess og aldur. Náttúrufræð-
ingurinn 28: 1—25.
Röthlisberger, H. 1972. Water pressure in intra-
and sub-glacial channels. J. Glaciology, 11:
62, Cambridge.
Thorarinsson, S., T. Einarsson and G. Kjartans-
son. 1959. On the Geology and Geomorpho-
logy of Iceland. Geogr. Annlr. 51: 135—169.
ÁGRIP
MÓTUN LANDS
í EFRI-LUNDARREYKJADAL
Margir drættir í eldri hluta Lundarreykjadals
sýna að land er þar mótað af rennsli undir
jökli. Rennslið hefur að hluta stjórnast af halla
yfirborðs jökulsins en að öðru leyti af dölum
undir jöklinum. Deigulmór og önnur jarðlög,
sem virðast hafa myndast undir fljótandi íshellu
hjá Lundi, benda til þess að breytingar á sjávar-
stöðu hafi ráðið miklu um myndun setlaga og
hegðun rennslis ofar í dalnum.
SvB.
JÖKULL 26. ÁR 7