Rit (Vísindafélag Íslendinga) - 01.07.1962, Qupperneq 85

83
fied crumbled mass and we now understand that it must be
creep in such original steep layers that creates the unstrati-
fied mass with crumbled bombs. In the stratified mass we
have an alternation of tuff and various grades of bomb frag-
ments as well as whole bombs. This fragmentation must
have occurred in the eruptive process, partly when the ma-
terial fell from the air. Only slight creep seems necessary to
produce, out of this material, the unstratified mass.
In our south section we see also the clear traces of another
Fig. 42. Hrafnabjörg, southern wall.
Explanation in the text.
process with similar but more thorough effects: Coming closer
to the west wall the breccia shows vertical shear planes and
the signs of more and more thorough grinding. A horizontal
prominent yellow tuff layer in the wall suddenly turns
straight down when traced into this mass. It is evident that
this was caused by vertical shearing movement, i.e. the up-
lift of the mountain out of the low ground, and formation
of dislocation breccia at the fault. When approaching and
going into the dislocation breccia we notice gradual changes:
First whole bombs disappear, then the glass crust on bomb
fragments disappears, and finally the fragments lose their
sharply angular shape.
Coming now higher in the main mass we meet original
stratification above about 520 m. These strata were deposited
on the lower crept mass after it had come to rest. First
stratification is only indicated by flattened bombs (flattened