Jökull - 01.12.1967, Page 23

Fig. 9. Refrozen “breccia”
of giacier ice left by the
hlaup on the margin of
its track, 75 m above the
valley floor. — Photo G.
Kjartansson, January 23,
1967.
9. mynd. Hrönn á hlaup-
mörkum undir Rjúpna-
felli. Samfrosið íshröngl
fyllir öll bil milli jak-
anna.
■
vanced over a plain of alluvium with braided
rivers. Its track following the river courses, first
that of the Krossá and then that of the Markar-
fljót, is 35 km long and in places more than
2 km wide. Artificial walls, built during the
last decades to protect the cultivatecl areas on
the plain against floods, prevented still wider
spreading out of this extraordinary flood. Only
the uppermost wall was overrun and partly
erodecl by the hlaup, otherwise it caused no
significant damage.
The flood in Markarfljót was the only phase
of the Steinsholt hlaup that was observed,
though in two places only, i.e. on a short
stretch visible from the farm Barkarstadir, and
on another still shorter stretch at the bridge,
Markarfljótsbrú. Owing to bad weather and
poor visibility the observations were not good.
The earth tremor registered at Kirkjubæjar-
klaustur, mentioned above, indicates that the
hlaup started (as rockslide) at 13 h. 47 min.
According to eyewitnesses the flood in the
Markarfljót reached Thórólfsfell, 9.5 km down
from the starting point of the rockslide, at 14 h.
15 min. ancl it passecl under the bridge, Mark-
arfljótsbrú, 24.5 km from the starting point, at
15 h. 35 min. (see Table I). Both timings may
be inaccurate by a few minutes. The duration
JÖKULL 17. ÁR 257