The position of our greater
mountain-chains sprawling across half the earth (the Pyrenees to
the Himalaya, and the Rocky Mountains to the Andes), seems to
confirm this, but the question of the interior of the earth is
obscure and disputed, and geologists generally conceive the rise
of land and formation of mountains in a different way. They are
due probably to the alteration of pressure on the crust in
combination with the instability of the interior. The floors of
the seas would sink still lower under their colossal burdens, and
this would cause some draining of the land-surface. At the same
time the heavy pressure below the seas and the lessening of
pressure over the land would provoke a reaction. Enormous masses
of rock would be forced toward and underneath the land-surface,
bending, crumpling, and upheaving it as if its crust were but a
leather coat. As a result, masses of land would slowly rise above
the plain, to be shaped into hills and valleys by the hand of
later time, and fresh surfaces would be dragged out of the deep,
enlarging the fringes of the primitive continents, to be warped
and crumpled in their turn at the next era of pressure.
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