Greinar (Vísindafélag Íslendinga) - 01.01.1977, Page 85

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A solid crystallized layer of basalt in a usual sense is no solu-
tion either: the magma would be crowded with basalt lumps.
Daly saw the only solution acceptable in broad terms: There
must be a general global layer of basaltic glass at magma
depths (57). But he could not specify the state of this glass,
nor could he solve the apparent disagreement with geophysics.
He withdrew publicly his theory. Later authors, like Rittman
in 1960 and Barth in 1962, dismissed the word glass, and spoke
instead of a basaltic substratmn, that was “potentially capable
of eruption and essentially mölecularly disperse" (58, p. 14).
For geophysicists and physicists this is extremely mystify-
ing, if they are determined not to understand geological lan-
guage. For those with physical education and geological ex-
perience, this is clear enough, and important. It is just an at-
tempt to express a general geological conclusion, without be-
ing unduely specific at the respective stage of knowledge.
The very weighty geological reasons for assuming a general
basaltic “magma” layer, are stated by Frechen (58) in this
way: Over 90% of all basalts are what he calls primary basalts,
i.e. close to those of flood basalts, shield volcanoes, and fissure
eruptions in chemical composition. There are variations, but
those of the main components are too small to obliterate the
fundamental rule, and could easily be explained by small-
scale differentiation, and small variations in the depth of the
source, because we can now prove that the composition of the
“potential” magma layer varies slightly with depth. The fur-
ther fundamental fact is this, in the authors’ translation of
Frechens’ words: “basalts in continental as well as in oceanic
regions have a worldwide distribution. Their composition has
remained strikingly uniform at all times and at all places”
(58, p. 14). And this naturally refers to the overwhelming
majority, the primary basalts. And these have “throughout
geological history again and again been erupted in great
amounts, with almost identical composition”. For this reason,
Frechen assumes that there cannot be a differentiation bet-
ween substratum and the primary basalt magma, and we con-
sider this to be an inference which must come rather close