Background Info:
The edge of a continental slope
may be modified in a number of
ways. In the Atlantic basin, where
the continental shelf is a
passive-margin, the ocean formed
as the fragments of Pangaea were
pushed apart by sea-floor
spreading originating at the
mid-Atlantic ridge. The base of
most of the world’s passive-margin
continental shelves is covered by a
layer of accumulated sediments
called the continental rise. In the
absence of the deep trenches of
subduction zones, these sediments,
which are deposited first on the
continental shelf and carried to the
slope by turbidity currents, build to
form a rise which may vary from
100 to 1,000 kilometers in width.
When a major river meets the
ocean near a continental shelf, the
sediment that is carried by the river
may be deposited, not only in a
delta, but in a fan which extends
over the edge of the shelf. The
Amazon Cone is an such a manner.
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