Columbia Libraries and the
Upper Mantle

SANDRA N. WARD AND ELLIS MOUNT

' HAT'S in a name? The word "mantle," for example,
means something entirely different to the fireplace
designer, the tailor, rhe chemist or the geologist. To
the geologist, it refers to a layer of the earth's interior, some i,8oo
miles thick. As noted in a recent book,* if we compare the earth
to a soft boiled egg, the yolk corresponds to the core, the white,
to the mantle, and the shell, to the earth's crust. The radius of
the earth is about 4,000 miles. The core, or yolk, extends from
the center to about 2,200 miles, and the mantle, or \vhite, accounts
for most of the remaining 1,800 miles of the radius. The crust, or
shell, which is the only part of the earth that we know from direct
observation, is relatively thin (3 to 40 miles).

For all of man's curiosity about his environment, he has yet to
explore beneath this thin outer crust. The deepest drill holes have
not yet reached the bottom of the crust! A\'hat knowledge we
have of the structure and composition of the earth below the crust
comes primarily from seismology, the study of earthquake waves
that have traveled through the interior layers.

A concerted effort is now being made to learn more about the
mantle, especially the uppermost 600 miles known as the "upper
mantle." Geologists and geophysicists believe that this part of the
solid earth has had \'erv great influence on the de\'elopment and
characteristics of the earth's surface as we know it today. Earth¬
quakes and volcanoes remind us that this influence continues.

The International Upper Mantle Project, a world-wide cooper-

* David B. Ericson and Goesta WoUin, The Ez'er-ehavgiiig Sea. New York,
Knopf, 1967. p. 265-6.

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