Continental Slope and Continental Rise
57
o
NW
- - -
..... 5km
I
o 80
m
100
120
SE
Fig. 2.9. Shelf break at the entrance of the Persian Gulf, subsurface echo profile by the research
vessel M eteor (1965). Note the accumulation of soft, layered sediment behind the rugged reef
structure. Upper slope collects reefal debris. The reef is dead. Shelf break is some what above 100 m
depth.
considered. However, such responses are difficult to separate from regional uplift and
subsidence.
2.9 Continental Slope and Continental Rise
The classic profile of Atlantic-type continental margins shows a steepening of the
slope at the shelf break and a gradually diminishing descent toward the deep sea floor
(Figs. 2.2 and 2.6). The relatively steep part below the shelf break ist the continental
slope; the gently descending part leading into the deep sea is the continental rise. The
boundary between slope and rise is ill-defined. Perhaps we can say that the slope is
definitely part of the margin, whereas the rise is built on oceanic crust and is essentially part of the deep-sea environment.
Not all slopes and rises , of course, fit the textbook outline of the ideal Atlantic
type - even in the Atlantic. Deep marginal ridges, as off Brazil, sheer walls of
outcropping ancient sediments, and deep-lying plateaus such as the Blake Plateau off
Florida can interrupt the ideal sequence.
The collision margins off Peru and Chile (Fig. 2.7a) are characterized by a steep
slope, without a rise - the trench swallows the material which would normally build
the rise. A descent in a series of steps is typical for the collision slope.
Rather complicated conditions prevail off much of the western US coast. While
the slope and rise off Northern California can be described simply enough in terms of
coalescing deep sea fan deposits (Fig. 2.10 northern part), no such description is
possible for the margin to the south. The Southern California Borderland looks much
like an extension of the basin-and-range topography familiar from the Mojave Desert,
into the sea. The tops of the ranges protrude as islands (Fig. 2.10 south-eastern part).
57
o
NW
- - -
..... 5km
I
o 80
m
100
120
SE
Fig. 2.9. Shelf break at the entrance of the Persian Gulf, subsurface echo profile by the research
vessel M eteor (1965). Note the accumulation of soft, layered sediment behind the rugged reef
structure. Upper slope collects reefal debris. The reef is dead. Shelf break is some what above 100 m
depth.
considered. However, such responses are difficult to separate from regional uplift and
subsidence.
2.9 Continental Slope and Continental Rise
The classic profile of Atlantic-type continental margins shows a steepening of the
slope at the shelf break and a gradually diminishing descent toward the deep sea floor
(Figs. 2.2 and 2.6). The relatively steep part below the shelf break ist the continental
slope; the gently descending part leading into the deep sea is the continental rise. The
boundary between slope and rise is ill-defined. Perhaps we can say that the slope is
definitely part of the margin, whereas the rise is built on oceanic crust and is essentially part of the deep-sea environment.
Not all slopes and rises , of course, fit the textbook outline of the ideal Atlantic
type - even in the Atlantic. Deep marginal ridges, as off Brazil, sheer walls of
outcropping ancient sediments, and deep-lying plateaus such as the Blake Plateau off
Florida can interrupt the ideal sequence.
The collision margins off Peru and Chile (Fig. 2.7a) are characterized by a steep
slope, without a rise - the trench swallows the material which would normally build
the rise. A descent in a series of steps is typical for the collision slope.
Rather complicated conditions prevail off much of the western US coast. While
the slope and rise off Northern California can be described simply enough in terms of
coalescing deep sea fan deposits (Fig. 2.10 northern part), no such description is
possible for the margin to the south. The Southern California Borderland looks much
like an extension of the basin-and-range topography familiar from the Mojave Desert,
into the sea. The tops of the ranges protrude as islands (Fig. 2.10 south-eastern part).