Continental Margin

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What is a Continental Margin?

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Among the major zones of the ocean floor, the continental margin is ranked as one of the three major zones. The other two zones being the deep-ocean basins and mid-ocean ridges. This continental margin is a shallow water area that is found nearby to the continents. 

This margin has mainly three different features: 

  • Continental rise

  • Continental slope

  • Continental shelf

The Continental margins consume about 28% of the area of the ocean.

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More About Continental Margins

Continental margins are on the leading edges of the tectonic plates, these are similar to the rim of the Pacific Ocean which are usually narrow and have steep continental slopes. In this case, either the poorly developed continental rises or none of the continents rises at all. The continental slope is often very steep and it falls directly into the trench in the deep sea.

The leading-edge margins are also supported by the mighty mountain ranges. The continental margins on the trailing side of the tectonic plates are those which are around the Atlantic Ocean; they are broad, featured with gentle continental slopes and with continental rise very well-developed. The adjacent land area that is commonly a coastal plain which is quite broad, depends on the state of the sea level, which may become submerged in different time intervals and thus form a part of the continental margin.

Passive Continental Margin

The passive margin is the transition that occurs between the oceanic area and continental. This is not an active plate margin. The passive margin is formed by the process of sedimentation which is above the ancient rift which is now marked by the transitional lithosphere. The continental rifting is created between the new ocean basins. After this, the continental rift makes a mid-ocean ridge and the locus of the extension moves away from the continent-ocean boundary. This transition between the continental and the oceanic lithosphere which was originally created by the rifting is called the passive margin.

These passive margins are found basically at every ocean and in the continent boundary which is not marked by the strike-slip fault or by the subduction zone. The passive margins also define the region around the Atlantic Ocean, Arctic Ocean and the western Indian Ocean. This also defines the entire coast of Africa, Greenland, India and Australia. They are also found on the east coast of the Northern America side and Southern America. Also, in western Europe and majorly in Antarctica. Eastern Asia also contains passive margins.

Types of Continental Margins

There are mainly two types of continental margins: 

  • Active Margins

  • Passive Margins

Active and Passive Continental Margins

An active continental margin is like a coastal region that is marked by mountain-building activity. This includes the earthquakes, volcanic activity, and tectonic motion thus resulting from the movement of the tectonic plates. The characteristics of the active continental margins include the following:

  • They are found majorly on the convergent plate boundaries

  • The continental slope also descends quite abruptly into a deep- ocean like trench (with no continental rise)

  • Location is somewhere around the Pacific Ocean.

The West Coast of the United States is also an active margin which is characterized by the rugged coastlines marked with narrow beaches and with steep sea cliffs.

On the other hand, we have passive continental margins which occur where the transition happens between the oceanic and between the continental crust. This is not an active plate. 

Examples of these passive margins are the Atlantic and the Gulf coastal regions that represent the setting where the thick accumulations of the sedimentary materials are buried with ancient rifts with continental boundaries formed from the opening of the Atlantic Ocean basin. This Atlantic Coast of the United States is also characterized by the wide beaches and barrier islands and also marked by the broad coastal plains.

Continental-Continental Convergent Plate Boundary

There are some lithospheric plates that consist of both the continental and the oceanic crust. The subduction which initiates as an oceanic lithosphere also slides quite beneath the continental crust. Here, when the oceanic lithosphere subducts to quite a greater depth, it then gets attached to the continental crust which is thereby pulled closer to the subduction zone and once while the continental lithosphere reaches this subduction zone, the subduction processes are then altered. 

Convergent Collision Plate Boundary

A convergent boundary which is also known as a destructive boundary is generally an area on the Earth’s surface where the two or more of the lithospheric plates collide with each other. One of these plates eventually slides beneath the other, and this process is known as subduction. This subduction zone can also be defined by a plane where many earthquakes happen.

FAQ (Frequently Asked Questions)

1. What Do You Mean By Sedimentation?

Ans. Sedimentation is the process where the particles in suspension tend to settle in the fluid. The particles tend to settle at that liquid in which they are entrained and then come to rest against the barrier. Settling is the falling of these suspended particles through the liquid, whereas in the process of sedimentation, the term is used to indicate the settling process.

2. What is the Lithosphere?

Ans. The lithosphere is the solid layer which forms the outer part of the Earth. This lithosphere includes the most brittle upper portion of the mantle and also comprises the crust. These are the outermost layers of the Earth's structure. They are bounded by the atmosphere which is above the asthenosphere (that is another part of the upper mantle) which is below the other layers.

3. What Do You Mean By ‘Continent-Ocean Boundary’?

Ans. The continent-ocean boundary also known as the COB or the continent-ocean is actually the transition boundary that occurs between the continental crust and the oceanic crust, this happens on a passive margin.