Greinar (Vísindafélag Íslendinga) - 01.01.1976, Page 112

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Special attention of researchers was attracted by dikes cutting
through the layers of plateau-basalts. It was suggested that the pre-
sence of a large number of dikes testifies to the enormous tension in
the Icelandic crust which from the time of the Paleocene till the
present could reach 400 km (6) and that this tension is a specific
“Icelandic” mechanism of the drift of continents. All these ideas
have, naturally, received support in the much advertised “ocean
floor spreading” hypothesis.
Let us, however, leave alone for some time the hypothetic ideas
and confine our analysis meanwhile only to that which can be
observed.
The dikes form in the east of Iceland several swarms. The mea-
surements of the total width of dikes in that region result in figures
not exceeding several kilometers. The authors of the cited paper
indicate, that along the length of one profile they reckoned 3 km
of dikes and along an other 2.3 km. Our measurements have shown
that within one swarm the total thickness of dikes did not exceed
0.5 km. A profile can be drawn across the eastem regions of Ice-
land which passes over 5 swarms. Consequently, the total thickness
of the visible dikes does not exceed 2.5 km, which coincides with
the data of the cited authors.
All the rest in the calculations of the latter is a combination of
more than just doubtful operations. Firstly, the authors assmned
that the dikes are distributed on the whole surface of Iceland with
the same frequency as in the eastem regions of the country. It has
been already shown that it is actually not so: on the north-westem
peninsula there are muoh fewer dikes within plateau-basalts than
in the east. Secondly, the authors for no reason whatever assumed
that each dike can bring to the surface a strictly definite voltune
of basalts and determined the total number of dikes proceeding
from the total volume of basalts composing Iceland. This calcula-
tion has nothing in common with geological reality, which shows
that one fissure can serve as the vent for colossal volumes of lavas,
while other cracks can stay amagmatic or contain “blind” dikes.
Thirdly, the mapping of dikes in the east of Iceland has shown
that their swarms are wedged out along the strike and by no means
cross all Iceland (see Fig. 1). As the result, it is easy to find direc-
tions transversal to the general strike which completely avoid