Oceanic Relief Features | UGC NET Geography | Solved PYQs

1. Kiel Canal connects. (SEPT 2013)

(1) Bering Sea and the Pacific Ocean
(2) Red Sea and the Mediterranean Sea
(3) Baltic Sea and North Sea
(4) Caribbean Sea and the Pacific Ocean

Correct Answer: (3) Baltic Sea and North Sea

The Kiel Canal is an important artificial waterway located in northern Germany. It connects the Baltic Sea with the North Sea, providing a direct maritime route for ships traveling between these two major water bodies. The canal extends from Brunsbüttel on the North Sea to Kiel-Holtenau on the Baltic Sea. It was officially opened in 1895 and is regarded as one of the busiest artificial shipping canals in the world.

The strategic importance of the Kiel Canal lies in the fact that it eliminates the need for vessels to travel around the Jutland Peninsula of Denmark through the Skagerrak and Kattegat straits. By using the canal, ships can shorten their journey by several hundred kilometers, resulting in significant savings in time, fuel, and transportation costs. This has made the canal a crucial link in European maritime trade and navigation.

The other options refer to different waterways. The connection between the Red Sea and the Mediterranean Sea is provided by the Suez Canal, while the connection between the Caribbean Sea and the Pacific Ocean is established by the Panama Canal. The Bering Sea and the Pacific Ocean are naturally connected through the Bering Strait region and are not linked by the Kiel Canal. For competitive examinations, the Kiel Canal is commonly associated with the connection between the Baltic Sea and the North Sea, making option (3) the correct answer.

2. Which of the following oceans is spreading due to tectonic plate movement? (SEPT 2013)

(1) Atlantic Ocean
(2) Pacific Ocean
(3) Indian Ocean
(4) Arctic Ocean

Correct Answer: (1) Atlantic Ocean

The Atlantic Ocean is spreading as a result of tectonic plate movement occurring along the Mid-Atlantic Ridge, a major underwater mountain chain that runs through the center of the ocean basin. The ridge marks a divergent plate boundary where the North American Plate and Eurasian Plate are moving apart in the northern section, while the South American Plate and African Plate are separating in the southern section. As these plates diverge, molten magma rises from the Earth’s mantle, cools, and forms new oceanic crust. This process is known as seafloor spreading.

The concept of seafloor spreading was developed through the work of geologists such as Harry Hess and became one of the key pieces of evidence supporting the Theory of Plate Tectonics. Geological studies have shown that the youngest oceanic rocks are found near the Mid-Atlantic Ridge, while older rocks occur farther away on either side, demonstrating the continuous creation of new crust and the gradual widening of the Atlantic Ocean basin.

In contrast, much of the Pacific Ocean is bordered by convergent plate boundaries and subduction zones collectively known as the Ring of Fire. In many places around the Pacific, oceanic crust is being destroyed faster than it is created, causing parts of the ocean basin to shrink. The Indian Ocean also contains spreading ridges, but the Atlantic Ocean is the classic and most widely cited example of an ocean expanding through seafloor spreading. The Arctic Ocean has limited spreading activity associated with the Gakkel Ridge, but its rate and extent are much smaller compared to the Atlantic. For this reason, geography and geology examinations commonly identify the Atlantic Ocean as the ocean that is spreading due to tectonic plate movement.

3. Flat topped seamounts are known as (SEPT 2013)

(1) Shoals
(2) Reefs
(3) Guyots
(4) Banks

Correct Answer: (3) Guyots

A guyot is a flat-topped underwater mountain or seamount that rises from the ocean floor but does not reach the sea surface. These features are usually volcanic in origin and were once islands that stood above sea level. Over long periods, the tops of these volcanic islands were eroded by waves, currents, and other coastal processes when they were at or near sea level. Later, due to subsidence of the oceanic crust and changes associated with plate tectonics, the islands gradually sank beneath the ocean surface, leaving behind a distinctive flat summit.

The term guyot was introduced by the American geologist Harry Hammond Hess in honor of the Swiss-American geographer and geologist Arnold Henry Guyot. The discovery and study of guyots provided important evidence for the concepts of continental drift and seafloor spreading, which later became integral parts of the Theory of Plate Tectonics. Many guyots are found in the Pacific Ocean, where chains of extinct volcanic islands and submerged mountains occur as tectonic plates move over stationary mantle hotspots.

The other options represent different marine features. Shoals are shallow areas in a body of water formed by sand, silt, or other sediments. Reefs are ridges or rock-like structures, often built by coral organisms, that occur near the water surface. Banks are broad, elevated portions of the continental shelf or seabed that are relatively shallow compared to surrounding waters. Among these features, only guyots specifically refer to flat-topped seamounts, making option (3) the correct answer.

4. Anacondas are largely found in (SEPT 2013)

(1) Irrawaddy basin
(2) Congo basin
(3) Orinoco basin
(4) Amazon basin

Correct Answer: (4) Amazon basin

Anacondas are among the largest and heaviest snakes in the world and are primarily found in the Amazon Basin of South America. They belong to the genus Eunectes, with the Green Anaconda being the most famous species. These giant snakes inhabit tropical rainforests, swamps, marshes, slow-moving rivers, and flooded grasslands where abundant water provides ideal conditions for their survival. Their eyes and nostrils are positioned on the top of the head, enabling them to remain mostly submerged while hunting prey.

The Amazon Basin is centered around the Amazon Basin and extends across several countries, including Brazil, Peru, Colombia, and others. This region contains the world’s largest tropical rainforest and one of the richest concentrations of biodiversity on Earth. The warm and humid equatorial climate, dense vegetation, and extensive river network create favorable habitats for large reptiles such as anacondas, caimans, and numerous aquatic species.

Although anacondas are also found in parts of the Orinoco Basin, particularly in Venezuela and neighboring regions, their principal distribution and greatest abundance are associated with the Amazon Basin. The Congo Basin in Africa is known for species such as pythons and crocodiles, while the Irrawaddy Basin in Myanmar supports a different range of fauna. In geography and environmental studies, the anaconda is commonly identified as a characteristic animal of the Amazon rainforest ecosystem, making option (4) the correct answer.

5. Sunda peninsula was submerged in the Pacific Ocean due to (SEPT 2013)

(1) Constructive activities of the plates
(2) Destructive activities of the plates
(3) Subduction of the plates into ocean
(4) Sea floor spreading

Correct Answer: (3) Subduction of the plates into ocean

The submergence of the Sunda landmass or Sunda Shelf region is associated with the process of subduction, in which one tectonic plate moves beneath another and descends into the Earth’s mantle. This phenomenon occurs at convergent plate boundaries, where oceanic and continental plates collide. The movement of plates in the Southeast Asian region has created complex geological structures, deep ocean trenches, volcanic arcs, and zones of crustal instability. Such tectonic activity has played a significant role in the fragmentation and partial submergence of land areas that once existed above sea level.

Subduction is a major component of the Theory of Plate Tectonics. When a denser oceanic plate converges with another plate, it is forced downward beneath the overriding plate. This process results in crustal deformation, earthquakes, volcanic activity, and the formation of deep oceanic trenches. The region around the Sunda Trench, located south of the Indonesian archipelago, is one of the world’s most active subduction zones. Here, the Indo-Australian Plate is moving beneath the Eurasian Plate, producing intense geological activity and contributing to changes in regional landforms over geological time.

The other options do not accurately explain the submergence. Constructive plate activities and sea-floor spreading are associated with divergent boundaries where new crust is created, often leading to the widening of ocean basins. Destructive plate activities is a broader term that includes crustal consumption, but the specific mechanism responsible is subduction. In physical geography and geology, the disappearance or sinking of land masses along active convergent margins is most directly linked to the process of subduction of tectonic plates, making option (3) the correct answer.

6. The greatest share of fisheries comes from (SEPT 2013)

(1) Deep seas
(2) Continental shelves
(3) Deep ocean trenches
(4) Fresh waters

Correct Answer: (2) Continental shelves

The greatest share of the world’s marine fisheries comes from the continental shelves. These are the gently sloping submerged extensions of continents that stretch from the coastline to the continental slope. Continental shelves are generally shallow, allowing sunlight to penetrate the water effectively. This promotes the growth of phytoplankton, which form the base of the marine food chain. The abundance of plankton supports large populations of fish, crustaceans, and other marine organisms, making continental shelf regions some of the most productive fishing grounds in the world.

The high biological productivity of continental shelf areas is also linked to the availability of nutrients supplied by rivers, coastal currents, and oceanic upwelling. Nutrient-rich waters encourage the growth of microscopic plants and organisms, which in turn sustain commercially important fish species. Many of the world’s leading fishing regions, such as the Grand Banks off the coast of Canada, the North Sea region of Europe, and the continental shelf waters around Japan, are located on extensive continental shelves.

In contrast, deep seas generally have lower biological productivity because sunlight cannot penetrate to great depths, limiting photosynthesis. Deep ocean trenches are among the least suitable areas for commercial fishing due to their extreme depths and relatively sparse marine life. Fresh waters contribute significantly to inland fisheries and aquaculture, but they account for a much smaller share of total global fish production compared to marine fisheries on continental shelves. For this reason, geography and economic geography studies identify the continental shelf as the principal source of the world’s marine fish catch and one of the most economically valuable parts of the ocean floor.

7. Diego Garcia is an island in which of the following oceans? (DEC 2013)

(1) Atlantic
(2) Pacific
(3) Indian
(4) Arctic

Correct Answer: (3) Indian

Diego Garcia is an island located in the Indian Ocean and forms part of the Chagos Archipelago. It lies in the central Indian Ocean, south of the Indian subcontinent and approximately midway between the eastern coast of Africa and the Indonesian region. The island is an atoll, meaning it is a ring-shaped coral formation surrounding a lagoon. Its geographical position gives it immense strategic importance in maritime and military affairs.

Diego Garcia is part of the Chagos Archipelago, which is administered as the British Indian Ocean Territory. The island gained international significance because of its location along major sea routes connecting the Middle East, East Africa, South Asia, and Southeast Asia. Owing to this strategic position, it hosts an important military facility jointly used by the United Kingdom and the United States.

From a geographical perspective, the Indian Ocean is the third-largest ocean in the world and serves as a crucial corridor for global trade and energy transportation. Diego Garcia occupies a central position within this oceanic region, making it a key reference point in studies of geopolitical geography, oceanic transport networks, and strategic maritime locations. The island is frequently mentioned in competitive examinations because of its location in the Indian Ocean and its significance in international affairs, maritime security, and global navigation.

8. Match List-I with List-II and select the correct answer using the codes given below (DEC 2013)

Codes

(1) A–II, B–III, C–I, D–IV
(2) A–IV, B–I, C–III, D–II
(3) A–III, B–II, C–IV, D–I
(4) A–I, B–IV, C–II, D–III

Correct Answer: (4) A–I, B–IV, C–II, D–III

The correct matching is A–I, B–IV, C–II, D–III. A coral reef is an organic ocean deposit formed by the accumulation of calcium carbonate skeletons secreted by coral polyps and other marine organisms. Coral reefs are among the most biologically productive marine ecosystems and are commonly found in warm, shallow tropical waters.

A shoal is a detached elevation with shallow depth that rises from the seabed and may pose hazards to navigation. Shoals are generally composed of sand, gravel, coral, or other sediments and occur in both coastal and offshore environments. Their relatively shallow depth distinguishes them from the surrounding deeper waters.

An abyssal plain is a vast deep flat surface found on the ocean floor, usually between the continental rise and the mid-oceanic ridge. Abyssal plains are among the flattest regions on Earth and are formed by the gradual accumulation of fine sediments over irregular volcanic terrain. These plains occupy large portions of the deep ocean basins and are important features of marine geomorphology.

The continental slope refers to the steep descent from the continental shelf toward the deeper ocean basin. It marks the transition between the shallow continental shelf and the deep ocean floor. The continental slope is often dissected by submarine canyons and represents one of the most prominent relief features of the ocean floor. In oceanography and geomorphology, understanding the relationship between coral reefs, shoals, abyssal plains, and continental slopes is essential for studying marine topography, ocean resources, and the structure of the Earth’s crust beneath the oceans.