Rit (Vísindafélag Íslendinga) - 01.07.1962, Page 66

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I have earlier rejected this mechanism as too artificial.
But I have also criticized in general the idea that the Pala-
gonite Formation should be considered as of subglacial origin.
This idea has never been founded on a detailed study: it
rests on general statements and analogies. The arguments are
about the following: in the post-glacial time Palagonite heaps
were not formed; apparently such heaps, with a high degree
of glass, need a special cooling agency to be formed. For a
Pleistocene formation it is natural to see this in subglacial
meltwater which will be present in great quantities as soon
as a subglacial eruption starts. Hence the simplest way to ex-
plain the fragmental volcanic masses is to assume subglacial
eruptions.
However, the matter is not so simple as this; there are
a great many details that do not fit into this scheme. In my
earlier paper on the Basic Tuffs (1946) I presented a number
of observations of details. These led me to the conclusion
that the Basic Tuff-Breccias have derived their peculiarities
from the state of the magma (low temperature and conse-
quently high viscosity) rather than from special external
cooling agencies. In the following we shall encounter many
detailed features of these rocks and shall then, at the end of
the paper be able to discuss their origin.
Hvalfell.
At the head of Hvalfjörður the Plateau Basalts reach a
height of 400—600 m. Into them is cut the valley Botnsdalur
in direct continuation of the fjord. After a short distance
this valley is abruptly closed by the volcano Hvalfell (848 m),
behind which is dammed the deep lake Hvalvatn. Before
Hvalfell was formed the valley had been fully developed and
deepened practically to its present level. Into a somewhat
hanging floor a 700 m broad channel with steep sides had
been eroded, Fig. 27. This channel most probably corresponds
to that found for instance in the Eyjafjörður valley (Einars-