The CIA World Factbook Every edition, 2022 to 2025 Oceans
Bathymetry Atlantic Ocean, in 4 editions.
The entry for Atlantic Ocean published Bathymetry in 4 editions of 36, from 2022 to 2025. The text changed in 2 editions. Each is shown as published. Bathymetry in every entry.
- editions changed the text
- 2
- the first edition with it
- 2022
- the latest edition with it
- 2025
Published as “Bathymetry” (2022 to 2025).
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2025 edition
Rewritten since 2024The same text in 2022 and 2023.
- continental shelf:
The continental shelf (see Figure 1), a rather flat area of the sea floor adjacent to the coast that gradually slopes down from the shore to water depths of about 200 m (660 ft). Dimensions can vary: they may be narrow or nearly nonexistent in some places or extend for hundreds of miles in others. The waters along the continental shelf are usually productive in both plant and animal life, both from sunlight and nutrients from ocean upwelling and terrestrial runoff.
The passive margins of the Atlantic Ocean provide for wide continental shelves in North America, Northwest Europe, and the southern coast of South America. The following are examples of features found on the continental shelf of the Atlantic Ocean.
Blake Plateau (Figure 5)
Celtic Shelf (Figure 2)
Dogger Bank (Figure 2)
Flemish Cap (Figure 2)
Falkland Plateau (Figure 3)
Grand Banks of Newfoundland (Figure 2)
Great Bahama Bank (Figure 5)
Little Bahama Bank (Figure 5)
Tunisian Plateau (Figure 4)
Yacatan Shelf (Figure 5)
- continental slope:
The c ontinental slope (see Figure 1) is where the ocean bottom drops off more rapidly until it meets the deep-sea floor ( abyssal plain ) at about 3,200 m (10,500 ft) water depth. The deep waters of the continental slope are characterized by cold temperatures, low light conditions, and very high pressures. Sunlight does not penetrate to these depths, having been absorbed or reflected in the water above. The continental slope can be indented by submarine canyons, often associated with the outflow of major rivers.
Another feature of the continental slope are alluvial fans or cones of sediments carried downstream to the ocean by major rivers and deposited down the slope. The following are examples of features found on the continental slope of the Atlantic Ocean.
Amazon Cone (Figure 3)
Congo Fan (Figure 3)
Hudson Canyon (Figure 5)
Mississippi Fan (Figure 5)
- abyssal plains:
The a byssal plains (see Figure 1), at depths of over 3,000 m (10,000 ft) and covering 70% of the ocean floor, are the largest habitat on earth. Sunlight does not penetrate to the sea floor, making these deep, dark ecosystems less productive than those along the continental shelf. Despite their name, these “plains” are not uniformly flat; they are interrupted by features like hills, valleys, and seamounts. The following are examples of features found on the abyssal plains of the Atlantic Ocean.
Angola Basin (Figure 3)
Agulhas Basin (Figure 3)
Argentine Basin (Figure 3)
Brazil Basin (Figure 3)
Canary Basin (Figure 2)
Cape Basin (Figure 3)
Colombia Basin (Figure 2)
Labrador Basin (Figure 2)
Mexico Basin (Figure 2)
Newfoundland Basin (Figure 2)
North American Basin (Figure 2)
Venezuela Basin (Figure 2)
West European Basin (Figure 2)
- mid-ocean ridge:
The mid-ocean ridge (see Figure 1), rising up from the abyssal plain , is an underwater mountain range, over 64,000 km (40,000 mi) long, rising to an average depth of 2,400 m (8,000 ft). Mid-ocean ridges form at divergent plate boundaries where two tectonic plates are moving apart and new crust is created by magma pushing up from the mantle. Tracing their way around the global ocean, this system of underwater volcanoes forms the longest mountain range on Earth.
Fracture Zones are linear transform faults that develop perpendicular to the line of the mid-ocean ridge which can offset the ridge line and divide it into segments.The Charlie-Gibbs Fracture Zone displaces the mid-ocean ridge 350 km to the west separating the Mid-Atlantic Ridge from the Reykjanes Ridge. The Romanche Fracture Zone, located near the Equator, offsets the Mid-Atlantic Ridge 900 km and is considered the dividing line between the North and South Atlantic Oceans. The following are examples of mid-ocean ridges found on the floor of the Atlantic Ocean.
East Mediterranean Ridge (Figure 4)
Mid-Atlantic Ridge (Figures 2, 3)
Reykjanes Ridge (Figure 2)
- seamounts:
Seamounts (see Figure 1) are submarine mountains at least 1,000 m (3,300 ft) high formed from individual volcanoes on the ocean floor. They are distinct from the plate-boundary volcanic system of the mid-ocean ridges , because seamounts tend to be circular or conical. A circular collapse caldera is often centered at the summit, evidence of a magma chamber within the volcano. Flat topped seamounts are known as guyots . Long chains of seamounts are often fed by "hot spots" in the deep mantle.
These hot spots are associated with stationary plumes of molten rock rising from deep within the Earth's mantle. These hot spot plumes melt through the overlying tectonic plate as it moves and supplies magma to the active volcanic island at the end of the chain of volcanic islands and seamounts . The following are examples of seamounts found on the floor of the Atlantic Ocean.
Bermuda Rise (Figure 2)
Cape Verde Plateau (Figure 2)
New England Seamounts (Figure 2)
Rio Grande Plateau (Figure 3)
Rockall Plateau (Figure 2)
- ocean trenches:
Ocean trenches (see Figure 1) are the deepest parts of the ocean floor and are created by the process of subduction. Trenches form along convergent boundaries where tectonic plates are moving toward each other, and one plate sinks (is subducted) under another. The location where the sinking of a plate occurs is called a subduction zone. Subduction can occur when oceanic crust collides with and sinks under (subducts) continental crust resulting in volcanic, seismic, and mountain-building processes.
Subduction can also occur in the convergence of two oceanic plates where one will sink under the other and in the process create a deep ocean trench . Subduction processes in oceanic-oceanic plate convergence also result in the formation of volcanoes. Over millions of years, the erupted lava and volcanic debris pile up on the ocean floor until a submarine volcano rises above sea level to form a volcanic island . Such volcanoes are typically strung out in chains called island arcs. As the name implies, volcanic island arcs, which closely parallel the trenches , are generally curved. The following are examples of ocean trenches found on the floor of the Atlantic Ocean.
Cayman Trench (Caribbean Sea) (Figure 2)
Hellenic Trench (Mediterranean Sea) (Figure 4)
Puerto Rico Trench (Figure 2); note - deepest point in the Atlantic Ocean
South Sandwich Trench (South Atlantic) (Figure 3)
- atolls:
Atolls are the remains of dormant volcanic islands. In warm tropical oceans, coral colonies establish themselves on the margins of the island. Then, over time, the high elevation of the island collapses and erodes away to sea level leaving behind an outline of the island in the form of the fringing coral reef. The resulting low island is typified by the coral reef surrounding a low elevation of sand and coral above sea level with an interior shallow lagoon.
Often times the remaining dry land is broken into a ring of islets. Some lagoons can be hundreds of square kilometers. It may take as long as 300,000 years for an atoll formation to occur. Guyots are submerged atoll structures, which explains why they are flat topped seamounts. The following are examples of atolls found in the Atlantic Ocean
Rocas Atoll (Brazil); note - the only atoll in the South Atlantic
continental shelf: The continental shelf (see Figure 1), a rather flat area of the sea floor adjacent to the coast that gradually slopes down from the shore to water depths of about 200 m (660 ft). Dimensions can vary: they may be narrow or nearly nonexistent in some places or extend for hundreds of miles in others. The waters along the continental shelf are usually productive in both plant and animal life, both from sunlight and nutrients from ocean upwelling and terrestrial runoff. The passive margins of the Atlantic Ocean provide for wide continental shelves in North America, Northwest Europe, and the southern coast of South America. The following are examples of features found on the continental shelf of the Atlantic Ocean.
Blake Plateau (Figure 5)
Celtic Shelf (Figure 2)
Dogger Bank (Figure 2)
Flemish Cap (Figure 2)
Falkland Plateau (Figure 3)
Grand Banks of Newfoundland (Figure 2)
Great Bahama Bank (Figure 5)
Little Bahama Bank (Figure 5)
Tunisian Plateau (Figure 4)
Yacatan Shelf (Figure 5)
continental slope: The c ontinental slope (see Figure 1) is where the ocean bottom drops off more rapidly until it meets the deep-sea floor ( abyssal plain ) at about 3,200 m (10,500 ft) water depth. The deep waters of the continental slope are characterized by cold temperatures, low light conditions, and very high pressures. Sunlight does not penetrate to these depths, having been absorbed or reflected in the water above. The continental slope can be indented by submarine canyons, often associated with the outflow of major rivers. Another feature of the continental slope are alluvial fans or cones of sediments carried downstream to the ocean by major rivers and deposited down the slope. The following are examples of features found on the continental slope of the Atlantic Ocean.
Amazon Cone (Figure 3)
Congo Fan (Figure 3)
Hudson Canyon (Figure 5)
Mississippi Fan (Figure 5)
abyssal plains: The a byssal plains (see Figure 1), at depths of over 3,000 m (10,000 ft) and covering 70% of the ocean floor, are the largest habitat on earth. Sunlight does not penetrate to the sea floor, making these deep, dark ecosystems less productive than those along the continental shelf. Despite their name, these “plains” are not uniformly flat; they are interrupted by features like hills, valleys, and seamounts. The following are examples of features found on the abyssal plains of the Atlantic Ocean.
Angola Basin (Figure 3)
Agulhas Basin (Figure 3)
Argentine Basin (Figure 3)
Brazil Basin (Figure 3)
Canary Basin (Figure 2)
Cape Basin (Figure 3)
Colombia Basin (Figure 2)
Labrador Basin (Figure 2)
Mexico Basin (Figure 2)
Newfoundland Basin (Figure 2)
North American Basin (Figure 2)
Venezuela Basin (Figure 2)
West European Basin (Figure 2)
mid-ocean ridge: The mid-ocean ridge (see Figure 1), rising up from the abyssal plain , is an underwater mountain range, over 64,000 km (40,000 mi) long, rising to an average depth of 2,400 m (8,000 ft). Mid-ocean ridges form at divergent plate boundaries where two tectonic plates are moving apart and new crust is created by magma pushing up from the mantle. Tracing their way around the global ocean, this system of underwater volcanoes forms the longest mountain range on Earth. Fracture Zones are linear transform faults that develop perpendicular to the line of the mid-ocean ridge which can offset the ridge line and divide it into segments.The Charlie-Gibbs Fracture Zone displaces the mid-ocean ridge 350 km to the west separating the Mid-Atlantic Ridge from the Reykjanes Ridge. The Romanche Fracture Zone, located near the Equator, offsets the Mid-Atlantic Ridge 900 km and is considered the dividing line between the North and South Atlantic Oceans. The following are examples of mid-ocean ridges found on the floor of the Atlantic Ocean.
East Mediterranean Ridge (Figure 4)
Mid-Atlantic Ridge (Figures 2, 3)
Reykjanes Ridge (Figure 2)
seamounts: Seamounts (see Figure 1) are submarine mountains at least 1,000 m (3,300 ft) high formed from individual volcanoes on the ocean floor. They are distinct from the plate-boundary volcanic system of the mid-ocean ridges , because seamounts tend to be circular or conical. A circular collapse caldera is often centered at the summit, evidence of a magma chamber within the volcano. Flat topped seamounts are known as guyots . Long chains of seamounts are often fed by "hot spots" in the deep mantle. These hot spots are associated with stationary plumes of molten rock rising from deep within the Earth's mantle. These hot spot plumes melt through the overlying tectonic plate as it moves and supplies magma to the active volcanic island at the end of the chain of volcanic islands and seamounts . The following are examples of seamounts found on the floor of the Atlantic Ocean.
Bermuda Rise (Figure 2)
Cape Verde Plateau (Figure 2)
New England Seamounts (Figure 2)
Rio Grande Plateau (Figure 3)
Rockall Plateau (Figure 2)
ocean trenches: Ocean trenches (see Figure 1) are the deepest parts of the ocean floor and are created by the process of subduction. Trenches form along convergent boundaries where tectonic plates are moving toward each other, and one plate sinks (is subducted) under another. The location where the sinking of a plate occurs is called a subduction zone. Subduction can occur when oceanic crust collides with and sinks under (subducts) continental crust resulting in volcanic, seismic, and mountain-building processes. Subduction can also occur in the convergence of two oceanic plates where one will sink under the other and in the process create a deep ocean trench . Subduction processes in oceanic-oceanic plate convergence also result in the formation of volcanoes. Over millions of years, the erupted lava and volcanic debris pile up on the ocean floor until a submarine volcano rises above sea level to form a volcanic island . Such volcanoes are typically strung out in chains called island arcs. As the name implies, volcanic island arcs, which closely parallel the trenches , are generally curved. The following are examples of ocean trenches found on the floor of the Atlantic Ocean.
Cayman Trench (Caribbean Sea) (Figure 2)
Hellenic Trench (Mediterranean Sea) (Figure 4)
Puerto Rico Trench (Figure 2); note - deepest point in the Atlantic Ocean
South Sandwich Trench (South Atlantic) (Figure 3)
atolls: Atolls are the remains of dormant volcanic islands. In warm tropical oceans, coral colonies establish themselves on the margins of the island. Then, over time, the high elevation of the island collapses and erodes away to sea level leaving behind an outline of the island in the form of the fringing coral reef. The resulting low island is typified by the coral reef surrounding a low elevation of sand and coral above sea level with an interior shallow lagoon. Often times the remaining dry land is broken into a ring of islets. Some lagoons can be hundreds of square kilometers. It may take as long as 300,000 years for an atoll formation to occur. Guyots are submerged atoll structures, which explains why they are flat topped seamounts. The following are examples of atolls found in the Atlantic Ocean
Rocas Atoll (Brazil); note - the only atoll in the South Atlantic
- continental shelf:
The continental shelf (see Figure 1), a rather flat area of the sea floor adjacent to the coast that gradually slopes down from the shore to water depths of about 200 m (660 ft). Dimensions can vary: they may be narrow or nearly nonexistent in some places or extend for hundreds of miles in others. The waters along the continental shelf are usually productive in both plant and animal life, both from sunlight and nutrients from ocean upwelling and terrestrial runoff.
The passive margins of the Atlantic Ocean provide for wide continental shelves in North America, Northwest Europe, and the southern coast of South America. The following are examples of features found on the continental shelf of the Atlantic Ocean:
Blake Plateau (Figure 5)
Celtic Shelf (Figure 2)
Dogger Bank (Figure 2)
Flemish Cap (Figure 2)
Falkland Plateau (Figure 3)
Grand Banks of Newfoundland (Figure 2)
Great Bahama Bank (Figure 5)
Little Bahama Bank (Figure 5)
Tunisian Plateau (Figure 4)
Yucatán Shelf (Figure 5)
- continental slope:
The c ontinental slope (see Figure 1) is where the ocean bottom drops off more rapidly until it meets the deep-sea floor ( abyssal plain ) at about 3,200 m (10,500 ft) water depth. The deep waters of the continental slope are characterized by cold temperatures, low light conditions, and very high pressures. Sunlight does not penetrate to these depths, having been absorbed or reflected in the water above. The continental slope can be indented by submarine canyons, which are often associated with the outflow of major rivers.
Another feature of the continental slope is alluvial fans, or cones of sediments, that major rivers carry downstream to the ocean and deposit down the slope. The following are examples of features found on the continental slope of the Atlantic Ocean:
Amazon Cone (Figure 3)
Congo Fan (Figure 3)
Hudson Canyon (Figure 5)
Mississippi Fan (Figure 5)
- abyssal plains:
The a byssal plains (see Figure 1), at depths of over 3,000 m (10,000 ft) and covering 70% of the ocean floor, are the largest habitat on earth. Sunlight does not penetrate to the sea floor, making these deep, dark ecosystems less productive than those along the continental shelf. Despite their name, these “plains” are not uniformly flat; they are interrupted by features like hills, valleys, and seamounts. The following are examples of features found on the abyssal plains of the Atlantic Ocean:
Angola Basin (Figure 3)
Agulhas Basin (Figure 3)
Argentine Basin (Figure 3)
Brazil Basin (Figure 3)
Canary Basin (Figure 2)
Cape Basin (Figure 3)
Colombia Basin (Figure 2)
Labrador Basin (Figure 2)
Mexico Basin (Figure 2)
Newfoundland Basin (Figure 2)
North American Basin (Figure 2)
Venezuela Basin (Figure 2)
West European Basin (Figure 2)
- mid-ocean ridge:
The mid-ocean ridge (see Figure 1), rising from the abyssal plain , is an underwater mountain range, over 64,000 km (40,000 mi) long, reaching an average depth of 2,400 m (8,000 ft). Mid-ocean ridges form at divergent plate boundaries where two tectonic plates are moving apart and magma pushing up from the mantle creates new crust. Tracing their way around the global ocean, this system of underwater volcanoes forms the longest mountain range on Earth.
Fracture zones are linear transform faults that develop perpendicular to the line of the mid-ocean ridge, which can offset the ridge line and divide it into segments. The Charlie-Gibbs Fracture Zone displaces the mid-ocean ridge 350 km to the west, separating the Mid-Atlantic Ridge from the Reykjanes Ridge. The Romanche Fracture Zone, located near the Equator, offsets the Mid-Atlantic Ridge 900 km and is considered the dividing line between the North and South Atlantic Oceans. The following are examples of mid-ocean ridges found on the floor of the Atlantic Ocean:
East Mediterranean Ridge (Figure 4)
Mid-Atlantic Ridge (Figures 2, 3)
Reykjanes Ridge (Figure 2)
- undersea terrain features:
The Abyssal Plain is commonly interrupted by a variety of commonly named undersea terrain features including seamounts , guyots , ridges , and plateaus .
Seamounts (see Figure 1) are submarine mountains at least 1,000 m (3,300 ft) high formed from individual volcanoes on the ocean floor. They are distinct from the plate-boundary volcanic system of the mid-ocean ridges, because seamounts tend to be circular or conical. A circular-collapse caldera is often centered at the summit, evidence of a magma chamber within the volcano. "Hot spots" in the deep mantle often feed long chains of seamounts.
These hot spots are associated with stationary plumes of molten rock rising from deep within the Earth's mantle. The hot-spot plumes melt through the overlying tectonic plate as it moves and supplies magma to the active volcanic island at the end of the chain of volcanic islands and seamounts.
Flat topped seamounts are known as guyots .
An undersea ridge is an elongated elevation of varying complexity and size, generally having steep sides.
An undersea plateau is a large, relatively flat elevation that is higher than the surrounding relief with one or more relatively steep sides. Although submerged, these features can reach close to sea level. The following are examples of undersea terrain features found on the floor of the Atlantic Ocean:
Bermuda Rise (Figure 2)
Cape Verde Plateau (Figure 2)
New England Seamounts (Figure 2)
Rio Grande Plateau (Figure 3)
Rockall Plateau (Figure 2)
- ocean trenches:
Ocean trenches (see Figure 1) are the deepest parts of the ocean floor and are created by the process of subduction. Trenches form along boundaries where tectonic plates are moving toward each other, and one plate sinks (is subducted) under another. The location where the sinking of a plate occurs is called a subduction zone. Subduction can occur when oceanic crust collides with and sinks under (subducts) continental crust, resulting in volcanic, seismic, and mountain-building processes. Subduction can also occur in the convergence of two oceanic plates, where one will sink under the other and in the process create a deep ocean trench.
Subduction processes in oceanic-to-oceanic plate convergence also result in the formation of volcanoes. Over millions of years, the erupted lava and volcanic debris pile up on the ocean floor until a submarine volcano rises above sea level to form a volcanic island . Such volcanoes are typically strung out in curved chains called island arcs.
The following are examples of ocean trenches found on the floor of the Atlantic Ocean:
Cayman Trench (Caribbean Sea) (Figure 2)
Hellenic Trench (Mediterranean Sea) (Figure 4)
Puerto Rico Trench (Figure 2); note - deepest point in the Atlantic Ocean
South Sandwich Trench (South Atlantic) (Figure 3)
- atolls:
Atolls are the remains of dormant volcanic islands. In warm tropical oceans, coral colonies establish themselves on the margins of the island. Then, over time, the high elevation of the island collapses and erodes away to sea level, leaving behind an outline of the island in the form of the fringing coral reef. The resulting low island is typified by the coral reef that surrounds a low elevation of sand and coral, with an interior shallow lagoon. Often the remaining dry land is broken into a ring of islets, and some lagoons can be hundreds of square kilometers.
Guyots are submerged atoll structures, which explains why they are flat-topped.
Rocas Atoll (Brazil) is the only atoll in the South Atlantic.
Rewritten: too little of the 2023 text remains to mark the changes.
continental shelf: The continental shelf (see Figure 1), a rather flat area of the sea floor adjacent to the coast that gradually slopes down from the shore to water depths of about 200 m (660 ft). Dimensions can vary: they may be narrow or nearly nonexistent in some places or extend for hundreds of miles in others. The waters along the continental shelf are usually productive in both plant and animal life, both from sunlight and nutrients from ocean upwelling and terrestrial runoff. The passive margins of the Atlantic Ocean provide for wide continental shelves in North America, Northwest Europe, and the southern coast of South America. The following are examples of features found on the continental shelf of the Atlantic Ocean:
Blake Plateau (Figure 5)
Celtic Shelf (Figure 2)
Dogger Bank (Figure 2)
Flemish Cap (Figure 2)
Falkland Plateau (Figure 3)
Grand Banks of Newfoundland (Figure 2)
Great Bahama Bank (Figure 5)
Little Bahama Bank (Figure 5)
Tunisian Plateau (Figure 4)
Yucatán Shelf (Figure 5)
continental slope: The c ontinental slope (see Figure 1) is where the ocean bottom drops off more rapidly until it meets the deep-sea floor ( abyssal plain ) at about 3,200 m (10,500 ft) water depth. The deep waters of the continental slope are characterized by cold temperatures, low light conditions, and very high pressures. Sunlight does not penetrate to these depths, having been absorbed or reflected in the water above. The continental slope can be indented by submarine canyons, which are often associated with the outflow of major rivers. Another feature of the continental slope is alluvial fans, or cones of sediments, that major rivers carry downstream to the ocean and deposit down the slope. The following are examples of features found on the continental slope of the Atlantic Ocean:
Amazon Cone (Figure 3)
Congo Fan (Figure 3)
Hudson Canyon (Figure 5)
Mississippi Fan (Figure 5)
abyssal plains: The a byssal plains (see Figure 1), at depths of over 3,000 m (10,000 ft) and covering 70% of the ocean floor, are the largest habitat on earth. Sunlight does not penetrate to the sea floor, making these deep, dark ecosystems less productive than those along the continental shelf. Despite their name, these “plains” are not uniformly flat; they are interrupted by features like hills, valleys, and seamounts. The following are examples of features found on the abyssal plains of the Atlantic Ocean:
Angola Basin (Figure 3)
Agulhas Basin (Figure 3)
Argentine Basin (Figure 3)
Brazil Basin (Figure 3)
Canary Basin (Figure 2)
Cape Basin (Figure 3)
Colombia Basin (Figure 2)
Labrador Basin (Figure 2)
Mexico Basin (Figure 2)
Newfoundland Basin (Figure 2)
North American Basin (Figure 2)
Venezuela Basin (Figure 2)
West European Basin (Figure 2)
mid-ocean ridge: The mid-ocean ridge (see Figure 1), rising from the abyssal plain , is an underwater mountain range, over 64,000 km (40,000 mi) long, reaching an average depth of 2,400 m (8,000 ft). Mid-ocean ridges form at divergent plate boundaries where two tectonic plates are moving apart and magma pushing up from the mantle creates new crust. Tracing their way around the global ocean, this system of underwater volcanoes forms the longest mountain range on Earth. Fracture zones are linear transform faults that develop perpendicular to the line of the mid-ocean ridge, which can offset the ridge line and divide it into segments. The Charlie-Gibbs Fracture Zone displaces the mid-ocean ridge 350 km to the west, separating the Mid-Atlantic Ridge from the Reykjanes Ridge. The Romanche Fracture Zone, located near the Equator, offsets the Mid-Atlantic Ridge 900 km and is considered the dividing line between the North and South Atlantic Oceans. The following are examples of mid-ocean ridges found on the floor of the Atlantic Ocean:
East Mediterranean Ridge (Figure 4)
Mid-Atlantic Ridge (Figures 2, 3)
Reykjanes Ridge (Figure 2)
undersea terrain features: The Abyssal Plain is commonly interrupted by a variety of commonly named undersea terrain features including seamounts , guyots , ridges , and plateaus .
Seamounts (see Figure 1) are submarine mountains at least 1,000 m (3,300 ft) high formed from individual volcanoes on the ocean floor. They are distinct from the plate-boundary volcanic system of the mid-ocean ridges, because seamounts tend to be circular or conical. A circular-collapse caldera is often centered at the summit, evidence of a magma chamber within the volcano. "Hot spots" in the deep mantle often feed long chains of seamounts. These hot spots are associated with stationary plumes of molten rock rising from deep within the Earth's mantle. The hot-spot plumes melt through the overlying tectonic plate as it moves and supplies magma to the active volcanic island at the end of the chain of volcanic islands and seamounts.
Flat topped seamounts are known as guyots .
An undersea ridge is an elongated elevation of varying complexity and size, generally having steep sides.
An undersea plateau is a large, relatively flat elevation that is higher than the surrounding relief with one or more relatively steep sides. Although submerged, these features can reach close to sea level. The following are examples of undersea terrain features found on the floor of the Atlantic Ocean:
Bermuda Rise (Figure 2)
Cape Verde Plateau (Figure 2)
New England Seamounts (Figure 2)
Rio Grande Plateau (Figure 3)
Rockall Plateau (Figure 2)
ocean trenches: Ocean trenches (see Figure 1) are the deepest parts of the ocean floor and are created by the process of subduction. Trenches form along boundaries where tectonic plates are moving toward each other, and one plate sinks (is subducted) under another. The location where the sinking of a plate occurs is called a subduction zone. Subduction can occur when oceanic crust collides with and sinks under (subducts) continental crust, resulting in volcanic, seismic, and mountain-building processes. Subduction can also occur in the convergence of two oceanic plates, where one will sink under the other and in the process create a deep ocean trench.
Subduction processes in oceanic-to-oceanic plate convergence also result in the formation of volcanoes. Over millions of years, the erupted lava and volcanic debris pile up on the ocean floor until a submarine volcano rises above sea level to form a volcanic island . Such volcanoes are typically strung out in curved chains called island arcs.
The following are examples of ocean trenches found on the floor of the Atlantic Ocean:
Cayman Trench (Caribbean Sea) (Figure 2)
Hellenic Trench (Mediterranean Sea) (Figure 4)
Puerto Rico Trench (Figure 2); note - deepest point in the Atlantic Ocean
South Sandwich Trench (South Atlantic) (Figure 3)
atolls: Atolls are the remains of dormant volcanic islands. In warm tropical oceans, coral colonies establish themselves on the margins of the island. Then, over time, the high elevation of the island collapses and erodes away to sea level, leaving behind an outline of the island in the form of the fringing coral reef. The resulting low island is typified by the coral reef that surrounds a low elevation of sand and coral, with an interior shallow lagoon. Often the remaining dry land is broken into a ring of islets, and some lagoons can be hundreds of square kilometers.
Guyots are submerged atoll structures, which explains why they are flat-topped.
Rocas Atoll (Brazil) is the only atoll in the South Atlantic.
- continental shelf:
the passive margins of the Atlantic Ocean provide for wide continental shelves in North America, Northwest Europe, and the southern coast of South America
the following are examples of features on the continental shelf of the Atlantic Ocean:
Blake Plateau (Figure 5)
Celtic Shelf (Figure 2)
Dogger Bank (Figure 2)
Flemish Cap (Figure 2)
Falkland Plateau (Figure 3)
Grand Banks of Newfoundland (Figure 2)
Great Bahama Bank (Figure 5)
Little Bahama Bank (Figure 5)
Tunisian Plateau (Figure 4)
Yucatán Shelf (Figure 5)
- continental slope:
the following are examples of features on the continental slope of the Atlantic Ocean:
Amazon Cone (Figure 3)
Congo Fan (Figure 3)
Hudson Canyon (Figure 5)
Mississippi Fan (Figure 5)
- abyssal plains:
the following are examples of features on the abyssal plains of the Atlantic Ocean:
Angola Basin (Figure 3)
Agulhas Basin (Figure 3)
Argentine Basin (Figure 3)
Brazil Basin (Figure 3)
Canary Basin (Figure 2)
Cape Basin (Figure 3)
Colombia Basin (Figure 2)
Labrador Basin (Figure 2)
Mexico Basin (Figure 2)
Newfoundland Basin (Figure 2)
North American Basin (Figure 2)
Venezuela Basin (Figure 2)
West European Basin (Figure 2)
- mid-ocean ridge:
- the Charlie-Gibbs Fracture Zone displaces the mid-ocean ridge 350 km to the west, separating the Mid-Atlantic Ridge from the Reykjanes Ridge;
- the Romanche Fracture Zone, located near the equator, offsets the Mid-Atlantic Ridge 900 km and is considered the dividing line between the North and South Atlantic Oceans
the following are examples of mid-ocean ridges on the floor of the Atlantic Ocean:
East Mediterranean Ridge (Figure 4)
Mid-Atlantic Ridge (Figures 2, 3)
Reykjanes Ridge (Figure 2)
- undersea terrain features:
the following are examples of undersea terrain features on the floor of the Atlantic Ocean:
Bermuda Rise (Figure 2)
Cape Verde Plateau (Figure 2)
New England Seamounts (Figure 2)
Rio Grande Plateau (Figure 3)
Rockall Plateau (Figure 2)
- ocean trenches:
the following are examples of ocean trenches on the floor of the Atlantic Ocean:
Cayman Trench (Caribbean Sea) (Figure 2)
Hellenic Trench (Mediterranean Sea) (Figure 4)
Puerto Rico Trench (Figure 2) - deepest point in the Atlantic
South Sandwich Trench (South Atlantic) (Figure 3)
- atolls:
- Rocas Atoll (Brazil) is the only atoll in the South Atlantic
Rewritten: too little of the 2024 text remains to mark the changes.
continental shelf: the passive margins of the Atlantic Ocean provide for wide continental shelves in North America, Northwest Europe, and the southern coast of South America
the following are examples of features on the continental shelf of the Atlantic Ocean:
Blake Plateau (Figure 5)
Celtic Shelf (Figure 2)
Dogger Bank (Figure 2)
Flemish Cap (Figure 2)
Falkland Plateau (Figure 3)
Grand Banks of Newfoundland (Figure 2)
Great Bahama Bank (Figure 5)
Little Bahama Bank (Figure 5)
Tunisian Plateau (Figure 4)
Yucatán Shelf (Figure 5)
continental slope: the following are examples of features on the continental slope of the Atlantic Ocean:
Amazon Cone (Figure 3)
Congo Fan (Figure 3)
Hudson Canyon (Figure 5)
Mississippi Fan (Figure 5)
abyssal plains: the following are examples of features on the abyssal plains of the Atlantic Ocean:
Angola Basin (Figure 3)
Agulhas Basin (Figure 3)
Argentine Basin (Figure 3)
Brazil Basin (Figure 3)
Canary Basin (Figure 2)
Cape Basin (Figure 3)
Colombia Basin (Figure 2)
Labrador Basin (Figure 2)
Mexico Basin (Figure 2)
Newfoundland Basin (Figure 2)
North American Basin (Figure 2)
Venezuela Basin (Figure 2)
West European Basin (Figure 2)
mid-ocean ridge: the Charlie-Gibbs Fracture Zone displaces the mid-ocean ridge 350 km to the west, separating the Mid-Atlantic Ridge from the Reykjanes Ridge; the Romanche Fracture Zone, located near the equator, offsets the Mid-Atlantic Ridge 900 km and is considered the dividing line between the North and South Atlantic Oceans
the following are examples of mid-ocean ridges on the floor of the Atlantic Ocean:
East Mediterranean Ridge (Figure 4)
Mid-Atlantic Ridge (Figures 2, 3)
Reykjanes Ridge (Figure 2)
undersea terrain features: the following are examples of undersea terrain features on the floor of the Atlantic Ocean:
Bermuda Rise (Figure 2)
Cape Verde Plateau (Figure 2)
New England Seamounts (Figure 2)
Rio Grande Plateau (Figure 3)
Rockall Plateau (Figure 2)
ocean trenches: the following are examples of ocean trenches on the floor of the Atlantic Ocean:
Cayman Trench (Caribbean Sea) (Figure 2)
Hellenic Trench (Mediterranean Sea) (Figure 4)
Puerto Rico Trench (Figure 2) - deepest point in the Atlantic
South Sandwich Trench (South Atlantic) (Figure 3)
atolls: Rocas Atoll (Brazil) is the only atoll in the South Atlantic
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Cite this page
Central Intelligence Agency. “Atlantic Ocean: Bathymetry.” The World Factbook, 2022–2025 editions. Archived by The Factbook, thefactbook.org/atlantic-ocean/bathymetry.