The emergence continues throughout the
Cretaceous (Chalk) period. Chains of vast mountains rise slowly
into the air in many parts of the earth, and a new and
comparatively rapid change in the vegetation--comparable to that
at the close of the Carboniferous--announces the second great
revolution. The Mesozoic closes with the dismissal of the great
reptiles and the plants on which they fed, and the earth is
prepared for its new monarchs, the flowering plants, the birds,
and the mammals.
How far this repeated levelling of the land after its repeated
upheavals is due to a real sinking of the crust we cannot as yet
determine. The geologist of our time is disposed to restrict
these mysterious rises and falls of the crust as much as
possible. A much more obvious and intelligible agency has to be
considered. The vast upheaval of nearly all parts of the land
during the Permian period would naturally lead to a far more
vigorous scouring of its surface by the rains and rivers. The
higher the land, the more effectively it would be worn down. The
cooler summits would condense the moisture, and the rains would
sweep more energetically down the slopes of the elevated
continents.
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