Geologists believe, in fact, that
the area of exposed land was probably greater than it is now.
This lifting and draining of so much land would of itself have a
profound influence on life-conditions, and then we must take
account of its indirect influence. The moisture of the earlier
period was probably due in the main to the large proportion of
sea-surface and the absence of high land to condense it. In both
respects there is profound alteration, and the atmosphere must
have become very much drier. As this vapour had been one of the
atmosphere's chief elements for retaining heat at the surface of
the earth, the change will involve a great lowering of
temperature. The slanting of the raised land would aid this, as,
in speeding the rivers, it would promote the circulation of
water. Another effect would be to increase the circulation of the
atmosphere. The higher and colder lands would create currents of
air that had not been formed before. Lastly, the ocean currents
would be profoundly modified; but the effect of this is obscure,
and may be disregarded for the moment.
Here, therefore, we have a massive series of causes and effects,
all connected with the great emergence of the land, which throw a
broad light on the change in the face of the earth.
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