Ocean Relief

Topography, in simple words, means the various elevations and depressions of an area. Topography of land often describes the physical features of the land, like the mountains, valleys, rivers, etc. As the name suggests, Ocean topography means studying the peaks and valleys present under the ocean. Over 70% of our planet consists of water, out of which only 3% are fresh water and the rest are oceans. So, almost 67% of our world is covered with ocean. So, studying and analyzing the Ocean topography becomes of utmost importance. When we study Ocean topography, we explore different relief features in the sea and many more things about these features.

What is Ocean relief meaning?

A question may have arisen in the readers' mind, what is ocean relief? 'Relief' in geography means the difference in height between the highs and lows of a piece of land. Relief is opposite to the word flatness. If we have to define it more qualitatively, it can be used as high-relief rolling hills or low-relief plain. Similarly, when the reliefs are present under the ocean, we call it ocean relief. Ocean relief or all reliefs formed due to continuous tectonic plate movements, volcanic eruption, erosions, and various types of deposition on the surface and the interaction between these processes over a million years. This creates a frequency of highs and lows on the land.

The relief of the ocean floor is called submarine relief or simply ocean relief or Ocean bottom relief.

Ocean relief features: 

The relief features of the ocean floor are mountains, valleys, basins, different ridges, plateaus, canyons, trenches, etc. As discussed earlier, these are formed due to millions of years of natural phenomena like tectonic movement, volcanic eruption, erosions, and depositions. Still, there is a difference between land relief and ocean relief. The oceanic crust is less than 70 million years, but the continental features are of the Proterozoic era, which means they are over 1 billion years old. This is why the characteristics of land relief and ocean relief may be similar in the process of formation but very different in their design.

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Classification of Oceanic features

The Oceanic features can be broadly classified into two parts: the major components and the minor features of Oceanic relief.

Major Oceanic Relief features:

The major oceanic relief features can be divided into four categories, Continental Shelf, Continental Slope, Continental Rise, Deep sea Plain, or the Abyssal Plain.

The Continental Shelf:

The Continental shelf is one of the major ocean relief features. The definition of a continental shelf and the criteria under which a coastal country or a coastal state can claim and establish the outer limits of its continental shelf are mentioned in Article 76 of the convention of the United Nations. A continental Shelf is a part of a continent submerged in the ocean but a relatively shallow water area. This area is known as the shelf area. These shelves are formed for many reasons, like the submergence of a part of the continent or the rise in the sea level. These shelves are created by wave erosion, where the land is eroded by seawater over millions of years. The gradient of this sloping is very gentle, like 1 in 500 for most of the continental shelves. When a shelf like that surrounds an Island, it is called an insular shelf. 

All the continental shelves cover about 7.5% of the total ocean area and about 18% of the earth's dry land area, which is why it comes under the major features of Oceanic relief. The width of a Shelf, if taken on average, is about 70-80 kilometers. 

The Continental Slope:

The Continental Slope is characterized as the zone stretching out from the shelf break and ending at the Continental rise where the angle turns out to be under 1:40 or where the slant is limited by a deep-sea trench or a marginal plateau. Albeit the slant is usually the steepest physiographic area of the continental margin, a solitary basic definition can't be given. Its width goes from 20 to 100 kilometers; its furthest cut-off at the shelf break ordinarily begins in water depths somewhere in the range of 100 and 200 meters; The slope region can be smooth or terraced, contain steep slopes or intra-slope basins, or be exceptionally unpredictable because of slumping, fault scarps, or diapirs. Most slants are cut transitionally at many spots in their upper part by submarine canyons associated with deep-sea fans, forming constructive sediment bodies on lower slopes, rise, trenches, and portions of the abyssal plain. 

Significance of Continental slope:

As the transition zone between the Continental shelf and the deep sea, the Continental Slope structures many sea-floor examinations for scientific, economic, and political reasons. Contrasting structural and depositional narratives bring about a variety of sediment suites and morphology. These elements consolidate in specific spaces to create conditions ideal for aggregating econo9mic quantities of oil and gas and selected hard minerals. 

Continental rise: 

A Continental rise is a more comprehensive, smoother grade from a deep-sea plain (abyssal plain) to a Continental slope. It generally has a very flat topology; it is sometimes crosscut by submarine canyons broadening offshore of Continental slope regions. 

For the most part, the mainland rise is missing in areas where deep-sea trenches exist where subduction zones are active.

Deep-Sea plain: 

Abyssal plains are abroad, gently slanted or almost flat area at Abyssal depths." Silt deposited nearby the continents forms the continental rise. This land-derived plain may stretch itself for many kilometers into the sea basins forming Abyssal plains. It is a relief of ocean floor.

Abyssal plains are remarkably level, having an incline of under 1:1,000 (or under 1 m change in tallness over a distance of 1 km) due to the thick silt wrap that covers most of the deep sea floors.

Minor Relief Features: 

Ridges: 

Submarine ridges expand hundreds and thousands of kilometers long and arrive at widths of a few hundred km. A few peaks regularly transcend ocean level to form islands. In the submarine continental margins, submarine ridges are somewhat uncommon, and their design is practically equivalent to the construction of mountains on the nearby pieces of the landmasses. In the transition zone, submarine edges show up predominantly as island arcs; they are likewise found at the bottom of deep-sea troughs of such peripheral seas as the Yamato, a ridge located in the sea of Japan or the Bowers in the Bering Sea. On the ocean floors, submarine ridges might be block, block-folding, or volcanic edges. 

Seamounts: 

Seamounts and Guyots are volcanoes that have developed from the seafloor, some of the time to the sea level or above. Guyots are seamounts that have built themselves over sea level. Disintegration by waves destroys the top of the seamount bringing about a straightened shape.

Trenches: 

Ocean Trenches are ocean bottom relief and are the steep troughs in the deepest parts of the sea [where old sea crust from one plate is pushed underneath another plate, raising mountains, causing earthquakes, and creating volcanoes on the seafloor ashore. With depths surpassing 6,000 meters (almost 20,000 feet), Trenches make up the world's "hadal zone," named for Hades, the Greek god of the underworld, and record for the deepest 45% of the global ocean. The deepest parts of a trench address just around 1% or less of its entire region. The slopes and vertical structures of trenches form a significant part of the hadal zone, where remarkable living spaces stretching out across a range of depths are home to a diverse number of species, a considerable lot of which are new or as yet unclear to science. 

Coral reefs: 

Coral reefs are enormous submerged constructions made out of the skeletons of colonial marine invertebrates called coral. Hermatypic, or "hard," corals are the corals that can form reefs since they separate calcium carbonate from seawater to make a complex, strong exoskeleton that secures their delicate, sac-like bodies. Different types of corals that are not engaged with reef-building are known as "soft" corals. 

Atolls: 

When a coral reef becomes ring-shaped, it's called Atoll. This atoll is made as a ring of coral that encompasses an undersea volcano that has risen above the water's surface. Long after the volcano has retreated into the sea, the atoll remains. The territory inside the atoll, shielded from the open sea by the sturdy reef, is known as a lagoon.