Jökull - 01.12.1967, Page 21

no sounding has ever been carried out in the
lake, it is not known whether similar or even
thicker sheet of debris was deposited on its
bottom. But as there is no indication that the
volume of thc lake basin was reduced to any
extent by the hlaup, it must be assumed tliat
the water was thrown uphill out of the basin.
However, two days later the basin had become
filled with water again and a new outlet deve-
loped.
The steep sides of the valley enclosing Steins-
holtslón and the Steinsholtsá show the effect
of the hlaup up to a more or less distinct limit.
Below this limit lay spread blocks of ice, the
ground was smeared with a skin of ntud, and
in many places it was scoured parallel to the
length of the valley in such a way that the
vegetation together with a thin layer of soil
had been stripped off. The thickness of this
layer, 1—2 cm, corresponds to the reach of
thawing into the frozen ground by the time of
the catastrophe. Brushes of willow and juniper
were crashed, struck down in the same direc-
tion, ancl the bark flayed off their stems.
On the other hand, minor and less resistant
remnants of the vegetation, like grass and
heather, lay stretched downhill mostly at right
angles to the scouring direction. They had ob-
viously been washed into that position.
The scouring and the other more crude signs
of havoc are certainly the effect of the rushing
of the main mass of the hlaup, but the wash-
ing must be due to water escaping from the
hlaup mass and flowing downhill immediately
after the main mass passed by.
d’he height reached by the hlaup on both
sides of the valley decreases on the whole to-
wards its mouth. But on the two bends of the
valley the limit lies much higher on the con-
cave, than on the convex, side. For instance:
(1) At the western end of the lake Steins-
holtslón the height limit on the right side lies
75 m above the valley floor. On the left side
the limit is not distinct but evidently not higher
Fig. 7. Cover of soil and vegetation on a huge block in the debris at the foot of the rock-
slide scarp. — Photo G. Kjartansson, July 1, 1967.
7. myncl. Úr urðarbingnum undir hrunstálinu. Hluti af krosssprungnu bergflikki með gróður-
torfum, sem hefur skriðið i heilu lagi ofan frá fjallsbrún.
JÖKULL 17. ÁR 255