399
Features of Deep-Ocean Basins
Features of Deep-Ocean Basins
Divergent Boundaries
Features of the Ocean Floor
Between the continental margin and the oceanic ridge lies the deep-ocean basin (see Figure
16.4). The size of this region—almost 30 percent of Earth’ s surface—is roughly comparable
to the percentage of land above sea level.
This region includes deep-ocean trenches,
which are extremely deep linear depressions
in the ocean floor; remarkably flat areas
known as abyssal plains; tall volcanic peaks
called seamounts and guyots; and large flood
basalt provinces called oceanic plateaus.
Deep-Ocean Trenches
Deep-ocean trenches are long, relatively narrow creases in the seafloor that represent the
deepest parts of the ocean floor (TABLE 16.1).
Most trenches are located along the margins
of the Pacific Ocean (FIGURE 16.8), where
many exceed 10 kilometers (6 miles) in
depth. A portion of one trench—the Challenger Deep in the Mariana Trench—has
been measured at 11,022 meters (36,163
feet) below sea level, making it the deepest
GEODe
ESSENTIALS
OF GEOLOGY
Philippine
trench
Aleutian trench
Kurile trench
Japan trench
Mariana trench
Java (Sunda)
trench
Kermadec trench
Central
America
trench
Bougainville trench
Tonga trench
Puerto-Rico
trench
Peru-Chile
trench
South Sandwich
trench
Ryukyu
Trench
FIGURE 16.8 Distribution of the world’s deep-ocean trenches.
known part of the world ocean. Two
trenches are located in the Atlantic—the
Puerto Rico Trench adjacent to the Lesser
Antilles arc and the South Sandwich Trench.
Trenches are sites of plate convergence
where slabs of oceanic lithosphere subduct
and plunge back into the mantle. In addition
TABLE 16.1
Dimensions of Some Deep-Ocean Trenches
Trench
Depth (kilometers) Average Width (kilometers) Length (kilometers)
Aleutian
7.7
50
3700
Central America
6.7
40
2800
Japan
8.4
100
800
Java
7.5
80
4500
Kurile–Kamchatka
10.5
120
2200
Mariana
11.0
70
2550
Peru–Chile
8.1
100
5900
Philippine
10.5
60
1400
Puerto Rico
8.4
120
1550
South Sandwich
8.4
90
1450
Tonga
10.8
55
1400
Features of Deep-Ocean Basins
Features of Deep-Ocean Basins
Divergent Boundaries
Features of the Ocean Floor
Between the continental margin and the oceanic ridge lies the deep-ocean basin (see Figure
16.4). The size of this region—almost 30 percent of Earth’ s surface—is roughly comparable
to the percentage of land above sea level.
This region includes deep-ocean trenches,
which are extremely deep linear depressions
in the ocean floor; remarkably flat areas
known as abyssal plains; tall volcanic peaks
called seamounts and guyots; and large flood
basalt provinces called oceanic plateaus.
Deep-Ocean Trenches
Deep-ocean trenches are long, relatively narrow creases in the seafloor that represent the
deepest parts of the ocean floor (TABLE 16.1).
Most trenches are located along the margins
of the Pacific Ocean (FIGURE 16.8), where
many exceed 10 kilometers (6 miles) in
depth. A portion of one trench—the Challenger Deep in the Mariana Trench—has
been measured at 11,022 meters (36,163
feet) below sea level, making it the deepest
GEODe
ESSENTIALS
OF GEOLOGY
Philippine
trench
Aleutian trench
Kurile trench
Japan trench
Mariana trench
Java (Sunda)
trench
Kermadec trench
Central
America
trench
Bougainville trench
Tonga trench
Puerto-Rico
trench
Peru-Chile
trench
South Sandwich
trench
Ryukyu
Trench
FIGURE 16.8 Distribution of the world’s deep-ocean trenches.
known part of the world ocean. Two
trenches are located in the Atlantic—the
Puerto Rico Trench adjacent to the Lesser
Antilles arc and the South Sandwich Trench.
Trenches are sites of plate convergence
where slabs of oceanic lithosphere subduct
and plunge back into the mantle. In addition
TABLE 16.1
Dimensions of Some Deep-Ocean Trenches
Trench
Depth (kilometers) Average Width (kilometers) Length (kilometers)
Aleutian
7.7
50
3700
Central America
6.7
40
2800
Japan
8.4
100
800
Java
7.5
80
4500
Kurile–Kamchatka
10.5
120
2200
Mariana
11.0
70
2550
Peru–Chile
8.1
100
5900
Philippine
10.5
60
1400
Puerto Rico
8.4
120
1550
South Sandwich
8.4
90
1450
Tonga
10.8
55
1400