Jökull - 01.12.1967, Page 26

area of 2 • 105 m2, and it was probably deep
enough (or more than 8—13 m on the average)
to account for the volume of the hlaup water.
However, another source of the water may
be possible. Actually, 1.5 • 107 m3 of rock, with
a density of 2.7, and falling 150 m, could gene-
rate sufficient heat to melt ice to yield 175,000
m3 of water. In the very special case of the
Steinsholt rockslide, which, falling onto a gla-
cier, plouged up and pushed foreward a huge
volume of ice, it might be expected that some
considerable fraction — say about 1/10 — of the
generated heat was consumed by melting of ice.
Furthermore, the valley sides transgressed by
the air-launched hlaup in Steinsholt had every-
where the pattern produced by water flowing
downhill. As this was also observed above the
lake Steinsholtslón, the hlaup evidently contain-
ed a considerable quantity of water before
reaching the lake. This water was probablv
released from the glacier by the energy of the
rockslide. But as this source of water is quite
insufficient and, in addition, not needed to
account for the volume of the flood water pass-
ing Markarfljótsbrú, it may be concluded that
Steinsholtslón was the onlv substantial source
of water for that flood.
REFEREN CES:
Kjartansson, G. 1967: Steinsholtshlaupið 15.
janúar 1967 (In Icelandic). Náttúrufræð-
ingurinn 57, 120—169.
Shreve, R. L. 1966: Sherman Landslide, Alaska.
Science 154, 1639—1642.
Fig. 12. View from the mountain side above the river plains of Steinsholtsá, Krossá ancl
Markarfljót. All the blocks seen spread over the plains are deposited by the hlaup. — Photo
G. Kjartansson June 30, 1967.
12. mynd. Horft úr hlíð Mosahauss niður yfir Steinsholtsdal og Markarfljótsaura. Öll stórgrýtis-
dreifin á flatlendinu er fram borin af hlaupinu.
260 JÖKULL 17. ÁR