Rit (Vísindafélag Íslendinga) - 01.06.1967, Side 25

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Suppose the original gap between Norway and Greenland
was 300 km wide and was occupied by Sial of 25 km thick-
ness. By a drift of 1200 km the gap was widened 5-fold and
if the Sial simply spread, it became 5 km thick, which by
isostasy would lead to a deep ocean. Another alternative is
that oceanic crust was formed in the gap. These two alter-
natives might be compared with seimic or petrographic data;
sofar such data do not seem to decide between these alter-
natives.
Trausti Einarsson (1963b) has discussed the idea that land
was formed in the widening gap by volcanic activity and
that later, subsidence took place.
It is tempting to assume that the Brito-Arctic flood basalts
are an expression of drift, but major masses of flood basalts
also occur within continents. It might also be thought that
the Mid-Atlantic Ridge is an expression of a continuation of
the drift which has been assumed here. But we must realize
that during the Cretaceous and much of the Tertiary, an in-
terval of 100 million years, relevant knowledge is lacking.
The drift of Greeland and the formation of the ridge may
be separated by such a long time and may be different pro-
cesses. From the admission of the drift of Greenland it does
not follow that drift has been in progress during the Upper
Tertiary or later.
2. Iceland.
In the geology and geophysics of Iceland we find data
relevant to the latest history of the Scandic and the Mid-
Atlantic Ridge as will now be considered (see also Trausti
Einarsson 1965).
The gravity field.
Fig. 8 shows the Bouguer anomaly for Iceland. The main
feature is a bowl with essentially the same shape as the
country. Even in details there are found striking similarities
in the outlines, cf. the Northwestem Peninsula, Fig. 9. This