Some portions of the earth are sinking while others are rising. The
millions of cubic feet of matter deposited daily in the oceans by
rivers would be sufficient to accomplish this. Every pound of matter
thus transferred, _is an energy transferred_. In the course of 1,000
years, 1,000 square miles of oceanic bottom would be covered to the
depth of 240 feet.
This enormous pressure on the underlying rocks is so much transferred
energy converted into mechanical heat. This must expand the rocks thus
under increased pressure. If this sediment were not borne into the
ocean along the Atlantic coast and spread out over vast areas it would
be lined with mountains and volcanoes, as that of the Mediterranean
sea; but being spread out over an extensive floor it prevents their
formation by lateral pressure.
Volcanoes are located where sediments can accumulate, and are doubtless
the result of this accumulation. Sixty-five thousand feet of steel
blocks piled one upon another would cause sufficient heat to melt the
lower ones or reduce them to a plastic state. The lava that issues from
a volcano is the deep bed-rock fused by pressure produced by lateral
expansion. Accumulating sediments cause rock expansion in some regions,
and being removed from others, causes contraction. Expansion elevates
the earth’s crust; contraction lowers it.
A downfall of water that would raise the ocean fifty feet above its
present level would cause an expansion that no rocks could resist, and
its lateral pressure must result in mountain making. The New England
coast has been elevated in comparatively recent times. The St. Lawrence
is so new that it has not yet swept its channel clean.
From Nova Scotia to Florida and around the whole boundary of the Gulf
of Mexico are the submerged shore-lines of a former continent. Many
miles out the lead-line suddenly plunges from about 100 fathoms to from
200 to 1,500 fathoms. So around the British Isles, the coast of Norway,
and that of Northern Europe and Asia. South America, Africa and the
Pacific present the same characteristics. The course of a submerged
continent has been traced in mid-ocean.