CHAPTER 1 An Introduction to Geology
26
In regions where trenches do not exist,
the steep continental slope merges into a
more gradual incline known as the
continental rise. The continental rise consists of a thick accumulation of sediments
that moved downslope from the continental shelf to the deep-ocean floor.
DEEP-OCEAN BASINS. Between the continental margins and oceanic ridges lie the
deep-ocean basins. Parts of these regions
consist of incredibly flat features called
abyssal plains. The ocean floor also contains extremely deep depressions that are
occasionally more than 11,000 meters
(36,000 feet) deep. Although these deepocean trenches are relatively narrow and
represent only a small fraction of the ocean
floor, they are nevertheless very significant
features. Some trenches are located adjacent to young mountains that flank the
continents. For example, in Figure 1.27 the
Peru–Chile trench off the west coast of
South America parallels the Andes Mountains. Other trenches parallel linear island
chains called volcanic island arcs.
Dotting the ocean floor are submerged
volcanic structures called seamounts,
which sometimes form long narrow chains.
Volcanic activity has also produced several
large lava plateaus, such as the Ontong Java
Plateau located northeast on New Guinea.
In addition, some submerged plateaus are
Philippine
Trench
Aleutian
Trench
Kurile
Trench
Japan Trench
Mariana Trench
Java (Sunda)
Trench
Kermadec Trench
Central
America
Trench
Tonga Trench
E a s t Pa ci fi c R is e
Juan de
Fuca
Ridge
Ryukyu
Trench
North
America
Arctic Ocean
Pacific Ocean
Australia
Bering
Abyssal
Plain
E lt a n in F ra c tu re Z o n e
Bellingshausen
Abyssal Plain
N .
A . C o r d il le ra
A p p a la c h i
a n s
D
iv
id
in
g
Range G
re
a
t
South
Tasman
Rise
Ontong-Java
Plateau
Manikiki
Plateau
Line Islands Ridge
Hawaii
Hess Rise
Shatsky
Rise
Shirshov
Ridge
Bowers
Ridge
Alaska
Seamounts
Campbell
Plateau
Galapagos
Rise
Alpine Fault
San Andreas
Fault
Basin and
Range
Province
Peru-Chile
trench
E m p er or S ea m o u n t
s
H a w a ii a n Is .
FIGURE 1.27 Major
surface features of the
geosphere.
26
In regions where trenches do not exist,
the steep continental slope merges into a
more gradual incline known as the
continental rise. The continental rise consists of a thick accumulation of sediments
that moved downslope from the continental shelf to the deep-ocean floor.
DEEP-OCEAN BASINS. Between the continental margins and oceanic ridges lie the
deep-ocean basins. Parts of these regions
consist of incredibly flat features called
abyssal plains. The ocean floor also contains extremely deep depressions that are
occasionally more than 11,000 meters
(36,000 feet) deep. Although these deepocean trenches are relatively narrow and
represent only a small fraction of the ocean
floor, they are nevertheless very significant
features. Some trenches are located adjacent to young mountains that flank the
continents. For example, in Figure 1.27 the
Peru–Chile trench off the west coast of
South America parallels the Andes Mountains. Other trenches parallel linear island
chains called volcanic island arcs.
Dotting the ocean floor are submerged
volcanic structures called seamounts,
which sometimes form long narrow chains.
Volcanic activity has also produced several
large lava plateaus, such as the Ontong Java
Plateau located northeast on New Guinea.
In addition, some submerged plateaus are
Philippine
Trench
Aleutian
Trench
Kurile
Trench
Japan Trench
Mariana Trench
Java (Sunda)
Trench
Kermadec Trench
Central
America
Trench
Tonga Trench
E a s t Pa ci fi c R is e
Juan de
Fuca
Ridge
Ryukyu
Trench
North
America
Arctic Ocean
Pacific Ocean
Australia
Bering
Abyssal
Plain
E lt a n in F ra c tu re Z o n e
Bellingshausen
Abyssal Plain
N .
A . C o r d il le ra
A p p a la c h i
a n s
D
iv
id
in
g
Range G
re
a
t
South
Tasman
Rise
Ontong-Java
Plateau
Manikiki
Plateau
Line Islands Ridge
Hawaii
Hess Rise
Shatsky
Rise
Shirshov
Ridge
Bowers
Ridge
Alaska
Seamounts
Campbell
Plateau
Galapagos
Rise
Alpine Fault
San Andreas
Fault
Basin and
Range
Province
Peru-Chile
trench
E m p er or S ea m o u n t
s
H a w a ii a n Is .
FIGURE 1.27 Major
surface features of the
geosphere.