Jökull - 01.12.1982, Page 66

Fig. 1. Map showing the main courses of the 1918 Katla debris flow.
Mynd 1. Kort sem synir meginstrauma Kötluhlaupsins 1918.
down the sandur plain along the bed of Múlakvísl
river into the sea, carrying enormous blocks ofice.
This continued to about 5,30 at which time the flow
increased markedly and seems to have reached its
maximum. At that time an eye-witness stated: “So
much ice was carried down between Hafursey and
Selfjall that it looked like snowcovered hills were
rushing forward" (Jóhannsson op. cit.). It is interest-
ing to note that this is partly suggestive, that the
glacier ice was mainly carried on top of the flow. See
Fig. 2 and discussion later. This may also explain
the fact that no kettle holes are found on Mýrdals-
sandur— contrary to Skeiðarársandur.
The flow rushed down on both sides of Hjörleifs-
höfði and covered the whole area ffom Kaplagarðar
to Lambajökull (Fig. 1). At the same time another
flow was rushing down from the north eastern side
of the glacier Kötlujökull onto Álftaver and along
the Hólmsá gorge. “The bridge of the Hólmsá was
washed ofF‘. At the end the ílow “covered all the
eastern Mýrdalssandur from Álftaver to Skaftár-
tunga except the highest ridges in Loðinsvíkur" —
and Ljósuvatnaháls. The total area of Mýrdals-
sandur from Múlakvísl to Kúðafljót including
Álftaver is approx. 600 km2. The 1918 flow seems at
its maximum to have covered 370-400 km2 (Eggerts-
son 1919).
The source ojthe debrisJlows.
On the 20th of October six men from the village of
Vík made an excursion to the glacier inorder to look
at the sourceof theflows. Amongstthem was Mr. G.
Jóhannsson, whose book contains the most extens-
ive descriptions of this event. From their observ-
62 JÖKULL 32. ÁR