Jökull - 01.12.1967, Blaðsíða 6

TABLE I
Station Ice thickness Quality Altitude of ice surface Altitude of glacial surf
metres of reflection m a. s. m a. s.
P1 260 good 1335 1075
9 200? poor 1280 1080?
3 250 good 1245 995
4 285 good 1250 965
5 300 poor 1240 940
6 370 fair 1370 1000
7 300 good 1200 900
8 320? poor 1320 1000?
9 315 good 1290 975
b) Measurement of the annual snow accu-
mulation. In addition to information on the
total thickness of tlie ice cover some data on
the accumulation of snow during the winter
of 1954/55 was obtained. On the very flat sur-
face around the base camp the thickness of the
winter snow layer was 920 cm with an average
specific gravity of 0.63 corresponding to pre-
cipitation as water of 5800 mm (Rist 1957). No
correction has though been made for possible
drift of snow into this depression. The tem-
perature of tlie snow was everywhere 0° C.
Dye tests showed that rain water percolated
down through the snow at a rate of more than
3 metres per day.
In other localities studied on the main ice
shield snow accumulation from the winter of
1954/55 was generally 4—6 metres correspond-
ing to an average precipitation as water of
3000 mm.
REFERENCES
Eythorsson, J. 195la: The thickness of Vatna-
jökull (Icelandic). Jökull 1, 1—6.
— 1951 b: The French-Icelandic expedition to
Vatnajökull, March—April 1951 (Icelandic).
Jökull 1, 10-14.
Holtzscherer, J. J. 1954: Expedition Franco-Is-
landaise au Vatnajökull Mars-avril 1951.
Resultants des sondages seismiques. Jökull
4, 1-33.
Rist, S. 1957: Snow survey on Icelandic glaciers
1954 and 1955 (Icelandic with English
Summary). Jökull 1, 33—36.
— 1960: Investigations on Vatnajiikull in
1960 (Icelandic with English Summary).
Jökull 11, 1-11.
Thorarinsson, S. 1959: On the possibilities of
predicting the next eruption of Katla (Ice-
landic with an English Summary). Jökull
9, 6-18.
Thorarinsson, S. and Rist, S. 1955: An investiga-
tion of Katla and the glacial burst from
Katla in the summer 1955. A preliminary
report (Icelandic). Jökull 5, 43—46.
ÞYKKT MÝRDALSJÖKULS
Sigurjón Rist,
Vatnamælingadeild Orkustofnunar.
ÁGRIP
a) Mæld var þykkt Mýrdalsjökuls á nokkrum
stöðum, sumarið 1935, og reyndist isþykktin frá
200 til 370 metrar.
b) Mœldur var snjór vetrarins 1954/55, og
reyndist hann víðast hvar 4 til 6 metra djúpur,
að vatni til um 3000 mm.
INNGANGUR
Mýrdalsjökull hefur mjög komið við sögu
þjóðarinnar. Því valda eldsumbrot í Kötlu
samfara ægilegum vatnsflóðum. Katla hefur
gosið allreglulega allt frá landnámsöld. Sigurð-
ur Þórarinsson (1959) telur sennilegt, að hún
hafi verið virk a. m. k. síðastliðin 10 þúsund
ár. Síðustu fjögur gosin voru 1755, 1823, 1860
og 1918. Auk hinna stóru vatnsflóða, sem eru
ferlegar náttúruhamfarir, koma iðulega hlaup-
skvettur úr jökullónum í randfjöllunum.
Árið 1955 samþykkti Aljtingi þingsályktunar-
240 JÖKULL 17. ÁR