The ocean bottom--a region nearly 2.5 times greater than the
total land area of the earth is a vast frontier that even today is
largely unexplored and uncharted. Until about a century ago, the
deep-ocean floor was completely accessible, hidden beneath waters
(1) ______ averaging
over 3, 600 meters deep. Totally without light and subjected intense
pressures hundreds of times greater than at the Earth’s
(2) ______ surface, the deep-ocean bottom is a hostile
environment to humans, in some ways as forbidding and remote as the void of
out space.
(3) ______ Therefore researchers have been taking samples
of deep-ocean
(4) ______ rocks and sediments for over a century, the first detailed
global investigation of the ocean bottom did actually start until 1968, with
(5) ______ the beginning of
the National Science Foundation’s Deep Sea Drilling Project (DSDP). Used
techniques first developed for the offshore
(6) ______ oil and gas industry, the DSDP’ s
drill ship, the Glomar Challenger, was able to maintain a steady position on
the ocean’s surface and drill very deep waters, extracting samples of
sediments and rock
(7) ______ from the ocean floor. The Glomar
Challenger’s core samples have allowed geologists to reconstruct that the
planet looked like hundreds of millions of years ago
(8) ______ and to calculate what it will probably look like millions of
years in the future. Today largely on the strength of evidence gathered
during the Glomar Challenger’s voyages, nearly all earth scientists agree
with the (9) ______ theories of
plate construction and continental drift that explain many of the geological
processes that shape on the Earth.
(10)
______