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Outlines of the Earth's History - A Popular Study in Physiography by Nathaniel Southgate Shaler
page 288 of 476 (60%)
many thousand feet. There are reasons to believe that on the floors of
the oceans this burial of beds containing water may have brought great
quantities of fluid to the depth of twenty miles or more below the
outer surface of the rocks.

[Illustration: Fig. 15.--Flow of lava invading a forest. A tree in the
distance is not completely burned, showing that the molten rock had
lost much of its original heat.]

The effect of deep burial is to increase the heat of strata. This
result is accomplished in two different ways. The direct effect
arising from the imposition of weight, that derived from the mass of
stratified material, is, as we know, to bring about a down-sinking of
the earth's crust. In the measure of this falling, heat is engendered
precisely as it is by the falling of a trip-hammer on the anvil, with
which action, as is well known, we may heat an iron bar to a high
temperature. It is true that this down-sinking of the surface under
weight is in part due to the compression of the rocks, and in part to
the slipping away of the soft underpinning of more or less fluid rock.
Yet further it is in some measure brought about by the wrinkling of
the crust. But all these actions result in the conversion of energy of
position into heat, and so far serve to raise the temperature of the
rocks which are concerned in the movements. By far the largest source
of heat, however, is that which comes forth from the earth's interior,
and which was stored there in the olden day when the matter forming
the earth gathered into the mass of our sphere. This, which we may
term the original heat, is constantly flowing forth into space, but
makes its way slowly, because of the non-conductive, or, as we may
phrase it, the "blanketing" effect of the outer rock. The effect of
the strata is the same as that exercised by the non-conductive
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