Minor Relief Of Ocean Floor| Class 11 Geography Notes

Minor relief of the ocean floor refers to the smaller-scale features that shape the underwater landscape. While the ocean floor might look smooth on a map. it’s a world of mountains, valleys, plains, and more just like the landmasses above the water.

In this article, You will get to know about the Minor relief of the Ocean floor, their features, and types.

Minor Relief Of Ocean Floor| Class 11 Geography Notes

What Does Ocean Relief Mean?

Ocean relief is the physical features of the ocean floor. The processes that create ocean relief features are plate tectonics, volcanic eruptions, erosion by currents and sediments, and deposition of sediments.

Ocean basins can be broadly divided into four regions continental shelf, continental slope, abyssal plain,, and deep ocean trenches. It is like the topography of land but underwater. Just like on land, the ocean floor is not flat. It has mountains, valleys, trenches, plains, and many other features.

Exploring the Minor Relief of the Oceans

Below are some of the minor relief features present on the ocean floor:

• Mid-Ocean Ridges
• Seamount
• Submarine Canyons
• Guyots
• Atoll
• Reefs
• Trenches
• Ridges
• Hills
• Fracture Zone
• Island Arcs
• Coral reefs
• Sea Scraps
• Submerged Volcanoes

Mid-Ocean Ridges

• Massive underwater mountain ranges along tectonic plate boundaries.
• These ridges consist of two chains of mountains separated by a large depression.
• These mountain ranges can have peaks as high as 2,500 m, with some even extending above the ocean’s surface.
• Examples of Mid-oceanic ridges include the South Atlantic Ridge in the Atlantic Ocean, the East Indian Ridge in the Indian Ocean, and the West Pacific Ridge in the Pacific Ocean.
• Longest mountain range on Earth, stretching globally for 65,000 km.
• A new ocean floor is created here through seafloor spreading.

Seamount

• Seamounts are mountains with pointed peaks that rise from the seafloor but do not reach the surface of the ocean.
• Isolated mountains rise from the ocean floor, but not reaching the surface.
• Volcanic in origin, formed by various processes like hotspot volcanism.
• Seamounts can be as tall as 3,000-4,500 m.
• An example of a seamount is the Cobb Seamount in the Pacific Ocean.

Submarine Canyons

• Deep, narrow valleys are carved into the seabed by underwater currents and erosion.
• Similar to canyons on land, but formed by different processes.
• The Capbreton Canyon in the Bay of Biscay and the Ganges Canyon in the Bay of Bengal are examples of submarine canyons.

Guyots

• Guyots are flat-topped seamounts, also known as table mounts.
• They are evidence of slow subsidence through various stages to become flat-topped submerged mountains.
• It is estimated that more than 10,000 guyots and seamounts are present in the Pacific Ocean alone.
• Formed when a seamount is eroded by waves and glaciers over time.

Atoll

• Ring-shaped coral reefs surround a central lagoon in tropical oceans.
• Form on top of submerged volcanoes or seamounts as coral reefs grow upwards.
• These are typically low islands found in tropical oceans.
• They may enclose a part of the sea (lagoon), or occasionally a body of brackish, fresh, or highly saline water.

Reefs

• Rocky ridges or underwater structures formed by the deposition of coral skeletons or other organisms.
• Provide important habitats for marine life.
• Coral reefs are a common feature of the Pacific Ocean, often associated with seamounts and guyots.
• The Great Barrier Reef off the coast of Australia is the world’s largest reef.
• As the reefs may extend above the surface, they can be dangerous for navigation.

Trenches

• Deep, elongated depressions near tectonic plate edges.
• Mariana Trench, the deepest point on Earth, is a trench.
• Formed when one tectonic plate subducts beneath another.

Ridges

• Long, narrow elevated areas on the seabed, not limited to mid-ocean ridges.
• Can be formed by various geological processes.
• Mid-ocean ridges are the most prominent ridges on the ocean floor.

Hills

• Relatively small, rounded elevations on the seabed.
• Smaller than mountains and formed by various geological processes.

Fracture Zone

• Imagine massive cracks in the Earth’s crust that extend underwater.
• These are fracture zones, marking areas where tectonic plates have shifted and broken.
• They can be associated with mid-ocean ridges and influence how plates move.

Island Arcs

• Curved chains of islands with volcanoes can erupt above subduction zones.
• These island arcs form as one tectonic plate dives beneath another, creating volcanoes and pushing up islands.

Sea Scraps

• These are steep slopes or cliffs on the seabed, often found along the edges of continental shelves or trenches. They can be formed by faulting, erosion, or mass wasting (underwater landslides).
• Marine debris refers to human-made waste that ends up in the ocean, including plastic bottles, bags, fishing gear, and other discarded items.
• sea scraps could refer to small pieces of rock, sediment, or other materials that have broken off from the seafloor due to natural processes like erosion or underwater landslides.

Submerged Volcanoes

Not all volcanoes reach the water’s surface. Submerged volcanoes are volcanic mountains that rise from the seabed but don’t break through the water. Seamounts can be formed by submerged volcanoes.

• Most submerged volcanoes are found along mid-ocean ridges, where tectonic plates are constantly spreading apart.

• Example of submerged Volcanoes – Located on the Juan de Fuca Ridge in the Pacific Ocean, Axial Seamount is a frequently erupting volcano with a summit just 250 meters below the surface.

The Four Major Types of Ocean Floor

The four major types of ocean floor can be categorized based on their depth and location relative to continents. Below are the major Four types of Ocean Floor are as following :

Continental Shelf

• Shallows area bordering the continents extending outward from the shoreline.
• Gently sloping seabed typically reaching depths of 130 to 200 meters (430 to 660 feet).
• Composed of continental rocks similar to those found on land.
• Important economic zone for fisheries and potential mineral resources.

Continental Slope

• The steeper region marks the transition from the continental shelf to the deep ocean floor.
• Slopes can range from 5 to 40 degrees reaching depths of 1,000 to 4,000 meters (3,300 to 13,000 feet).
• Composed of sediments eroded from continents and organic material from surface waters.
• Home to submarine canyons carved by underwater currents and sediment flows.

Abyssal Plain

• A vast, relatively flat region that covers most of the ocean floor.
• Lies at depths of 3,000 to 6,000 meters (9,800 to 19,700 feet) on average.
• Composed of thick layers of sediment deposited over millions of years from organic material, windblown dust and volcanic ash.
• Abyssal plains are home to diverse deep-sea life adapted to the cold dark environment.

Oceanic Trenches

• The deepest depressions on Earth’s surface are located near the edges of tectonic plates.
• Can reach depths exceeding 11,000 meters (36,000 feet) with the Mariana Trench being the deepest point.
• Formed when one tectonic plate subducts beneath another pushing the other plate down.
• Home to unique ecosystems adapted to the extreme pressure and darkness.

Conclusion – Class 11 Minor Relief of the Ocean Floor

The ocean floor despite appearing vast and flat on a world map. It is a place of dramatic variations in topography. These smaller features that make up the ocean floor are termed minor relief features.

Some of the most common features of minor relief of the ocean floor are Mid-Oceanic Ridges, Seamounts, Guyots, Trenches, Submarine Canyons and Atolls.

FAQs on Class 11 Minor Relief of the Ocean Floor

What is the relief of the ocean floor?

The ocean water consists of a considerable variety of landscapes very similar to its counterpart on the continents.There are Mountains , basins , plateaus , ridges , canyons and trenches beneath the ocean water .These relief fatures found on the ocean floor are called ocean relief or submarine relief.

What creates an Ocean floor?

Bathymetry, the shape of the ocean floor is largely a result of a process called Plate Techtonics .The outer rocky layer of the Earth includes about a dozen large sections called tectonic plates that are arranged like a spherical jig-saw puzzle floating on top of the Earth’s hot flowing mantle.

What are the relief features of the Indian Ocean floor?

The bottom relief of Indian Ocean resembles that of the Atlantic Ocean.This ocean has a continuous central ridge, called the Arabic-Indian Ridge, together with its southern extension, the Kerguelen-Gaussberg Ridge, which connects with the Antarctic continent.

What are the 4 types of ocean floor?

The major 4 types of ocean floors are The Continential Shelf , The Contenential Slope ,Abyssal Plains and Ocean trenches .

Why Trenches are so deep?

Trenches are formed by subduction, a geophysical process in which two or more of Earth’s tectonic plates converge and the older, denser plate is pushed beneath the lighter plate and deep into the mantle, causing the seafloor and outermost crust (the lithosphere) to bend and form a steep, V-shaped depression.