At most places along the boundary
of every continent is an area of
shallow water which may range
from a few kilometers to more than
1,000 kilometers in width. These
areas, where the oceans cover a
portion of the continental land
mass, are called continental
shelves. Averaging approximately
60 meters in depth, these shelves
slope gradually away from the
shore at a rate of about 12 meters
every kilometer. At the edge of the
continental shelf is an area called
the continental slope, a much
steeper zone that drops away to
the ocean floor.
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