The molten ocean below would surge through the crust, and
bury it under floods of lava. Some hold that the slabs would sink
in the ocean of metal, and thus the earth would first solidify in
its deeper layers. There would, in any case, be an age-long
struggle between the molten mass and the confining crust, until
at length--to employ the old Roman conception of the activity of
Etna--the giant was imprisoned below the heavy roof of rock.
Here again we seem to find evidence of the general correctness of
the theory. The objection has been raised that the geologist does
not find any rocks which he can identify as portions of the
primitive crust of the earth. It seems to me that it would be too
much to expect the survival at the surface of any part of the
first scum that cooled on that fiery ocean. It is more natural to
suppose that millions of years of volcanic activity on a
prodigious scale would characterise this early stage, and the
"primitive crust" would be buried in fragments, or dissolved
again, under deep seas of lava. Now, this is precisely what we
find, The oldest rocks known to the geologist--the Archaean
rocks--are overwhelmingly volcanic, especially in their lower
part.
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