Oceanography- 1 | Geography for UPSC 2024 (Pre & Mains) PDF Download

 Page 1


 
OCEANOGRAPHY - 1 
RELIEF OF THE OCEAN FLOOR 
 
 
- The oceans are confined to the great depressions of the earth’s outer 
layer. 
- The oceans, unlike the continents, merge so naturally into one another 
that it is hard to demarcate them. 
- The geographer’s have divided the oceanic part of the earth into oceans, 
like the Pacific, the Atlantic, the Indian ocean etc. 
- The various seas, bays, gulfs and outer inlets are parts of these large 
oceans. 
- A major portion if the ocean floor is found between 3-6 km below the 
sea level. 
- The land, under the waters of the oceans, that is, the ocean floor 
exhibits complex and varied features as those observed over the land. 
- The floors of the oceans are rugged with the world’s largest mountain 
ranges, deepest trenches and the largest plains. 
- These features are formed, like those of the continents, by the factors 
of tectonic, volcanic and depositional processes. 
 
 
 
Page 2


 
OCEANOGRAPHY - 1 
RELIEF OF THE OCEAN FLOOR 
 
 
- The oceans are confined to the great depressions of the earth’s outer 
layer. 
- The oceans, unlike the continents, merge so naturally into one another 
that it is hard to demarcate them. 
- The geographer’s have divided the oceanic part of the earth into oceans, 
like the Pacific, the Atlantic, the Indian ocean etc. 
- The various seas, bays, gulfs and outer inlets are parts of these large 
oceans. 
- A major portion if the ocean floor is found between 3-6 km below the 
sea level. 
- The land, under the waters of the oceans, that is, the ocean floor 
exhibits complex and varied features as those observed over the land. 
- The floors of the oceans are rugged with the world’s largest mountain 
ranges, deepest trenches and the largest plains. 
- These features are formed, like those of the continents, by the factors 
of tectonic, volcanic and depositional processes. 
 
 
 
 
 
 
DIVISIONS OF THE OCEAN FLOOR 
 
- The ocean floors can be divided into four major divisions: 
? The continental shelf 
? The continental slope 
? The deep sea plain 
? The oceanic deep 
Besides these divisions, there are also major and minor relief features in the 
ocean floors like ridges, hills, sea mountains, guyots, trenches, canyons, 
etc. 
1. CONTINENTAL SHELF 
Page 3


 
OCEANOGRAPHY - 1 
RELIEF OF THE OCEAN FLOOR 
 
 
- The oceans are confined to the great depressions of the earth’s outer 
layer. 
- The oceans, unlike the continents, merge so naturally into one another 
that it is hard to demarcate them. 
- The geographer’s have divided the oceanic part of the earth into oceans, 
like the Pacific, the Atlantic, the Indian ocean etc. 
- The various seas, bays, gulfs and outer inlets are parts of these large 
oceans. 
- A major portion if the ocean floor is found between 3-6 km below the 
sea level. 
- The land, under the waters of the oceans, that is, the ocean floor 
exhibits complex and varied features as those observed over the land. 
- The floors of the oceans are rugged with the world’s largest mountain 
ranges, deepest trenches and the largest plains. 
- These features are formed, like those of the continents, by the factors 
of tectonic, volcanic and depositional processes. 
 
 
 
 
 
 
DIVISIONS OF THE OCEAN FLOOR 
 
- The ocean floors can be divided into four major divisions: 
? The continental shelf 
? The continental slope 
? The deep sea plain 
? The oceanic deep 
Besides these divisions, there are also major and minor relief features in the 
ocean floors like ridges, hills, sea mountains, guyots, trenches, canyons, 
etc. 
1. CONTINENTAL SHELF 
 
 
- The continental shelf is the extended margin of each continent 
occupied by relatively shallow seas. 
- The shelf is formed mainly due to 
• submergence of a part of a continent 
• relative rise in sea level 
• Sedimentary deposits brought down by rivers 
-  
- It is the shallowest part of the ocean showing an average gradient of 1 
degree or even less. 
- The shelf typically ends at a very step slope, called the shelf break. 
- The width of the continental shelves vary from one ocean to another. 
- The average width of continental shelves is about 80 km. 
- The continental shelves are covered with variable thickness of 
sediments brought down by rivers, glaciers, wind, from the land and 
distributed by waves and currents. Massive sedimentary deposits 
received over a long time by the continental shelves, become the 
source of fossil fuels. 
- Marine food comes almost entirely from continental shelves 
- They provide the richest fishing grounds 
- They are potential sites for economic minerals 
Page 4


 
OCEANOGRAPHY - 1 
RELIEF OF THE OCEAN FLOOR 
 
 
- The oceans are confined to the great depressions of the earth’s outer 
layer. 
- The oceans, unlike the continents, merge so naturally into one another 
that it is hard to demarcate them. 
- The geographer’s have divided the oceanic part of the earth into oceans, 
like the Pacific, the Atlantic, the Indian ocean etc. 
- The various seas, bays, gulfs and outer inlets are parts of these large 
oceans. 
- A major portion if the ocean floor is found between 3-6 km below the 
sea level. 
- The land, under the waters of the oceans, that is, the ocean floor 
exhibits complex and varied features as those observed over the land. 
- The floors of the oceans are rugged with the world’s largest mountain 
ranges, deepest trenches and the largest plains. 
- These features are formed, like those of the continents, by the factors 
of tectonic, volcanic and depositional processes. 
 
 
 
 
 
 
DIVISIONS OF THE OCEAN FLOOR 
 
- The ocean floors can be divided into four major divisions: 
? The continental shelf 
? The continental slope 
? The deep sea plain 
? The oceanic deep 
Besides these divisions, there are also major and minor relief features in the 
ocean floors like ridges, hills, sea mountains, guyots, trenches, canyons, 
etc. 
1. CONTINENTAL SHELF 
 
 
- The continental shelf is the extended margin of each continent 
occupied by relatively shallow seas. 
- The shelf is formed mainly due to 
• submergence of a part of a continent 
• relative rise in sea level 
• Sedimentary deposits brought down by rivers 
-  
- It is the shallowest part of the ocean showing an average gradient of 1 
degree or even less. 
- The shelf typically ends at a very step slope, called the shelf break. 
- The width of the continental shelves vary from one ocean to another. 
- The average width of continental shelves is about 80 km. 
- The continental shelves are covered with variable thickness of 
sediments brought down by rivers, glaciers, wind, from the land and 
distributed by waves and currents. Massive sedimentary deposits 
received over a long time by the continental shelves, become the 
source of fossil fuels. 
- Marine food comes almost entirely from continental shelves 
- They provide the richest fishing grounds 
- They are potential sites for economic minerals 
 
 
EXAMPLES: 
- The shelves are almost absent or very narrow along some of the 
margins like the coasts of chile, the west coast of Sumatra, etc. 
- On the contrary, the Siberian shelf in the arctic ocean, the largest in 
the world, stretches to 1500km in width. 
 
 
 
 
2. CONTINETAL SLOPE 
Page 5


 
OCEANOGRAPHY - 1 
RELIEF OF THE OCEAN FLOOR 
 
 
- The oceans are confined to the great depressions of the earth’s outer 
layer. 
- The oceans, unlike the continents, merge so naturally into one another 
that it is hard to demarcate them. 
- The geographer’s have divided the oceanic part of the earth into oceans, 
like the Pacific, the Atlantic, the Indian ocean etc. 
- The various seas, bays, gulfs and outer inlets are parts of these large 
oceans. 
- A major portion if the ocean floor is found between 3-6 km below the 
sea level. 
- The land, under the waters of the oceans, that is, the ocean floor 
exhibits complex and varied features as those observed over the land. 
- The floors of the oceans are rugged with the world’s largest mountain 
ranges, deepest trenches and the largest plains. 
- These features are formed, like those of the continents, by the factors 
of tectonic, volcanic and depositional processes. 
 
 
 
 
 
 
DIVISIONS OF THE OCEAN FLOOR 
 
- The ocean floors can be divided into four major divisions: 
? The continental shelf 
? The continental slope 
? The deep sea plain 
? The oceanic deep 
Besides these divisions, there are also major and minor relief features in the 
ocean floors like ridges, hills, sea mountains, guyots, trenches, canyons, 
etc. 
1. CONTINENTAL SHELF 
 
 
- The continental shelf is the extended margin of each continent 
occupied by relatively shallow seas. 
- The shelf is formed mainly due to 
• submergence of a part of a continent 
• relative rise in sea level 
• Sedimentary deposits brought down by rivers 
-  
- It is the shallowest part of the ocean showing an average gradient of 1 
degree or even less. 
- The shelf typically ends at a very step slope, called the shelf break. 
- The width of the continental shelves vary from one ocean to another. 
- The average width of continental shelves is about 80 km. 
- The continental shelves are covered with variable thickness of 
sediments brought down by rivers, glaciers, wind, from the land and 
distributed by waves and currents. Massive sedimentary deposits 
received over a long time by the continental shelves, become the 
source of fossil fuels. 
- Marine food comes almost entirely from continental shelves 
- They provide the richest fishing grounds 
- They are potential sites for economic minerals 
 
 
EXAMPLES: 
- The shelves are almost absent or very narrow along some of the 
margins like the coasts of chile, the west coast of Sumatra, etc. 
- On the contrary, the Siberian shelf in the arctic ocean, the largest in 
the world, stretches to 1500km in width. 
 
 
 
 
2. CONTINETAL SLOPE 
 
 
- The continental slope connects the continental shelf and the ocean 
basins or its floor. 
- It begins where the bottom of the continental shelf sharply drops off 
into a steep slope. 
- The gradient of the slope region varies between 2-5 degrees. 
- The depth of the slope region varies between 200 and 3000m. 
- The slope boundary indicates the end of the continents. 
- Canyons and trenches are observed in this region. 
 
3. DEEP SEA PLAIN 
- Deep sea plains are generally sloping areas of the ocean basins, 
- These are the flattest and the smoothest regions of the world.  
- The depths vary between 3000 and 6000 m. 
- These plains are covered with fine-grained sediments like clay and 
silt.