Rit (Vísindafélag Íslendinga) - 01.07.1962, Blaðsíða 123

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in connection with other craters on the table mountains, such
as Herðubreið and Bláfjall which could be of rather high
Pleistocene age in spite of the relatively fresh state.
Immediately at the foot of the south and west slope of
Geitahlíð we have the dolerite surface of a lower block, at
100 m elevation, the surface then falling by 1° south to the
30—40 m high sea cliff Krísuvíkurberg. The displacement
at Geitahlíð is about 150 m.
In the sea cliff 8—10 lavas can be seen. Mostly there is
only scoriae in between, but in one case the surface of a lava
was much weathered and broken up by frost into large blocks
and flakes. The covering lava was very fluid, being pressed
Fig. 60. Krísuvíkurbjarg; lava resting on weathering debris.
into even very narrow spaces between the flakes, cf. Fig. 60.
In rather early post-glacial time the cliff was just as now.
The Krísuvíkurhraun flowed over its edge and formed a 150
—200 m broad rim in front; the old edge peeps out at many
places through the post-glacial lava.
The dolerite lavas have a very even surface and are much
different in this respect from the rough post-glacial block
lavas. This indicates not only high fluidity but also the un-
interrupted spread of a great lava mass, for slowing up of
a front always leads to block lavas.
In the southern part of the area the dolerite surface is com-
pletely broken up by frost action and no certain glacial ve-
stiges are found. But close to Geitahlíð the surface is glacially
striated in a souúieasterly direction. Yery conspicuous here
is also a thick brown to grey hard conglomerate covering the