Submarine canyons definition and discussion

Table of Contents

Introduction

Various geo-natural variations like hills, mountains, plateaus, etc. can be observed on the land. Similarly, in the study of oceanography, it is known that the topography of the bottom of the ocean is also diverse. Because there are volcanoes, ridges, highlands, canyons, deep trenches, etc. on the ocean floor. The submarine canyon is one of them. Definition and discussions of submarine canyons are as below.

There are many canyons found at depths of more than 2 km below sea level. Submarine canyons are one of them. A submarine canyon is a steep-sided valley located on the seafloor of a continental slope. They are very deep and narrow. It often extends from the mouths of large rivers.

Ocean relief is the seabed or subsea water known as ‘land’ that forms complex and varied features. There are two types of ocean relief. These are major relief features and minor relief features on the ocean floors. A submarine canyon is a minor relief feature on the ocean floors. They are located within a small area but their depth is unusually high (1).

Definition

A narrow steep-sided valley that is cut into the continental slopes and continental rises of the oceans is called a submarine canyon (3).

Features

Some interesting features of submarine canyons are as follows.

1. They sometimes extend well up to the continental shelf.

2. It is cut into the seabed of the continental slope.

3. Many submarine canyons are found at depths of more than 2 km below sea level.

4. More common on steep slopes found on active margins than on gentle slopes found on passive margins.

5. They show erosion through all strata from lithified sediments to crystalline rocks.

6. Canyons are steeper, shorter, more dendritic, and more closely spaced on active than on passive continental margins.

7. Its walls are usually very steep and can be near vertical.

8. There are an estimated 9,477 submarine canyons on earth, covering about 11% of the continental slope.

9. The walls of such canyons are eroded by organic erosion.

10. They resemble canyons made by rivers on land.

11. Their length is usually 50 to 300 km.

12. The axes of such canyons are usually aligned normally to the coastline.

13. Over geologic time, submarine canyons are formed by the erosion of slopes by turbulent currents flowing down the canyon axis (2) & (4).

Functions

Act as channels for turbulent currents.
It transports sediments from land and the shelf to the deep sea environment.
This type of canyons plays an important role in the biodiversity of the underwater ecological system (3).

Example

The Congo River canyon in Africa
Scripps and Monterey canyons in California
the “No Ground” channel incised into the Ganges-Brahmaputra Delta in Bangladesh
The Sepic River in Papua New Guinea (1).

Formation

They were carved during the ice age, when the sea level was about 125 m below the present sea level and rivers flowed along the edge of the continental shelf. This type of canyon is formed by erosion and mass wasting.
The main mechanisms of submarine canyons are turbidity currents and underwater landslides.
Turbidity currents are dense, sediment-laden currents that flow downslope when an unstable mass of rapidly deposited sediment on the upslope fails, perhaps due to earthquakes.
There is a spectrum of turbidity or density currents, ranging from “muddy water” to massive mudflows, and evidence of both these extreme members can be observed in deposits associated with the deeper parts of submarine canyons.
Submarine canyons that are particularly deep. In some cases, an ocean with a seabed significantly below sea level is separated from the larger ocean to which it is normally connected.
Seas that are normally filled by inflows and outflows from the ocean are no longer filled and therefore dry out over time, which may be less if the local climate is drier.
Rivers that previously flowed into the sea now cut deeper into the bottom of the sea beds, forming submarine canyons. Submarine canyons have eroded and are now located far below the present sea level (1) & (4).

Structure

Are V-shaped valleys. It is cut into the steep-sided continental slope. This type of canyon is formed at the outer edge of the continental shelf and continues across the slope. Its lower end is usually fan-shaped, which is a big pile of sediment lying on the ocean floor (3).

Importance in ecology

Interactions between submarine canyon topography and ocean currents have profound consequences for the diversity, function, and dynamics of both pelagic and benthic communities.
Currents flowing through it likely increase primary productivity and transport sediment and associated particle-reactive materials into the deep environment.
Can be hotspots of animal productivity due to high levels of primary productivity.
The highly variable seascapes within submarine canyons support diverse assemblages of different species that play a great role in ecology.
They often give rise to enhanced biodiversity across small spatial scales and maintain ecosystem function.
Submarine canyons represent a relevant regional source of marine biodiversity and ecosystem functioning (2).

Written By: Manisha Bharati

Q&A

1. Submarine canyons are usually found in which region?

Submarine canyons are usually found in the continental margin of southern California, and Baja California.

2. How do submarine canyons form?

They are formed by turbidity currents. It is likely caused by earthquakes or other extreme forces that cause underwater sediment avalanches. As gravity takes hold of the dense mixture of debris and water moves down the slope, carving submarine canyons.

3. Turbidity currents carry sediments into submarine canyons which may eventually produce

Turbidity currents carry sediments into submarine canyons that can eventually form deep-sea fans. These currents slow down and deposit sediment on the continental rise as deep-sea fans in continental zones.

4. What are submarine canyons?

A submarine canyon is a narrow steep-sided and v-shaped valley that is cut into the continental slopes and continental margin of the oceans.

5. How are submarine canyons formed?

Mainly formed through erosion and mass wasting.