Environmental Engineering Reference
In-Depth Information
1
The Blue Zone of the Planet Earth
…
The sculptures on the ocean basin
Can never be created by human machine
…
.
The Authors
1:1000. Seaward from the continental shelf is the
continental slope, which extends to a depth of
1.6
1.1
Sculptures of the Ocean Basin
and Estuary
3.2 km. The continental slope has a gradient
between 1:2 and 1:40. The extent of the sloping
can vary from a gradual drop to a steep decline
into an ocean trench, as illustrated by the slope that
occurs off the western coast of South America.
Because of the steepness of the angle, the conti-
nental slope usually has less sediment.
Some continental slopes have submarine
canyons that are similar to canyons found on
land. Many of these submarine canyons are
aligned with river systems on land and were
probably formed by these rivers during periods
of low sea level. The Hudson River canyon on
the East Coast of the USA is an example of this.
Other submarine canyons have ripple marks on
the
-
The ocean basin has unique designs and sculptures
similar to the land features above it. Mountain
ranges, canyons, valleys, and vast plains are all the
important components of the underwater land-
scape. These physical features of the ocean bottom
are called bathygraphic features, and unlike their
counterpart topographic features on land, they
change at relatively slow pace. Erosion is slow in
the relatively calm recesses of the ocean, and
changes are mainly attributed to sedimentation,
uplifting, and subsidence.
The structures and features of ocean basin are
represented in Figs.
1.1
and
1.2
.
Brief descriptions of these features are given
here:
oor, and at the ends of the canyons, sedi-
ments fan out, suggesting that they were formed
by moving sediments and water. Oceanographers
believe that these canyons were formed by tur-
bidity currents. Turbidity currents are swift ava-
lanches of sediment and water that erode a slope
as they sweep down and pick up speed. At the
end of the slope, the current slows and the sed-
iments fan out. Turbidity currents can be caused
by earthquakes or the accumulation of large
amounts of sediments on steep slopes that over-
load the slope
fl
Continental Margin
The continental margin includes the continental
shelf and slope. At the edge of a continent is the
continental shelf (Fig.
1.2
). Continental shelves
are generally
at areas, averaging 68 km
(40 miles) in width and 130 m (430 ft) in depth,
that slope gently towards the bottom of the ocean
basin. The width of a continental shelf is fre-
quently related to the slope of the land it borders.
Mountainous coasts, like the West Coast of the
USA, usually have a narrow continental shelf,
whereas low-lying land, like the East Coast of the
USA, usually has a wide one. Continental shelves
are actually part of the continents to which they are
attached. The criterion for de
fl
'
s capacity to hold them.
Continental Rise
At the base of a steep continental slope, there
may be a gentle slope called a continental rise.
A continental rise is produced by processes such
as landslides that carry sediments to the bottom
of the continental slope. Most continental rises
are located in the Atlantic and Indian Oceans and
ning the seaward
edge of the continental shelf is a marked change in
slope. The continental shelf has a gradient of about
