Active Vs Passive Continental Margins

Zone of the ocean floor that separates the thin oceanic chaff from thick continental chaff

Contour illustrating the shelf, slope and ascent

A continental margin is the outer edge of continental crust abutting oceanic crust under littoral waters. It is i of the three major zones of the ocean flooring, the other 2 being deep-ocean basins and mid-bounding main ridges. The continental margin consists of three dissimilar features: the continental rise, the continental slope, and the continental shelf.^[1] The continental shelf is the relatively shallow water area institute in proximity to continents. Continental margins establish near 28% of the oceanic area.^[2]

Zones of the continental margin [edit]

The continental shelf is the portion of the continental margin that transitions from the shore out towards to ocean. Continental shelves are believed to make up 7% of the sea floor.^[3] The width of continental shelves worldwide varies in the range of 0.03–1500 km.^[four] The continental shelf is mostly flat, and ends at the shelf break, where there is a drastic increase in slope angle: The hateful bending of continental shelves worldwide is 0° 07′, and typically steeper closer to the coastline than information technology is near the shelf break.^[v] At the shelf break begins the continental slope, which tin can be 1–five km to a higher place the deep-ocean flooring. The continental slope often exhibits features chosen submarine canyons.^[iv] Submarine canyons often cut into the continental shelves deeply, with nigh vertical sides, and continue to cut the morphology to the deep-sea plain.^[5] These canyons are oftentimes V-shaped, and can sometime enlarge onto the continental shelf. At the base of the continental slope, there is a sudden decrease in slope angle, and the sea floor begins to level out towards the abyssal plain. This portion of the seafloor is chosen the continental rise, and marks the outermost zone of the continental margin.^[one]

Types [edit]

There are two types of continental margins: active and passive margins.^[1]

Active margins are typically associated with lithospheric plate boundaries. These active margins tin exist convergent or transform margins, and are also places of high tectonic activity, including volcanoes and earthquakes. The West Coast of North America and South America are active margins.^[four] Active continental margins are typically narrow from coast to shelf break, with steep descents into trenches.^[4] Convergent active margins occur where oceanic plates meet continental plates. The denser oceanic crust of one plate subducts below the less dumbo continental crust of some other plate. Convergent agile margins are the most common blazon of active margin. Transform agile margins are more rare, and occur when an oceanic plate and a continental plate are moving parallel to each other in contrary directions. These transform margins are often characterized by many offshore faults, which causes high caste of relief offshore, marked by islands, shallow banks, and deep basins. This is known as the continental borderland.^[one]

Passive margins are often located in the interior of lithospheric plates, away from the plate boundaries, and lack major tectonic action. They ofttimes face mid-body of water ridges.^[3] From this, comes a broad diverseness of features, such as low-relief state extending miles abroad from the beach, long river systems and piles of sediment accumulating on the continental shelf.^[6] The East Coast of the The states is an example of a passive margin. These margins are much wider and less steep than agile margins.

Sediment aggregating [edit]

Every bit continental chaff weathers and erodes, it degrades into mainly sands and clays. Many of these particles end upward in streams and rivers that so dump into the bounding main. Of all the sediment in the stream load, 80% is and then trapped and dispersed on continental margins.^[3] While modern river sediment is oft notwithstanding preserved closer to shore, continental shelves show loftier levels of glacial and relict sediments, deposited when ocean level was lower.^[3] Frequently plant on passive margins are several kilometres of sediment, consisting of terrigenous and carbonate (biogenous) deposits. These sediment reservoirs are often useful in the report of paleoceanography and the original formation of sea basins.^[three] These deposits are oftentimes non well preserved on active margin shelves due to tectonic activity.^[four]

Economic significance [edit]

The continental shelf is the nearly economically valuable part of the ocean. Information technology often is the most productive portion of the continental margin, as well as the most studied portion, due to its relatively shallow, accessible depths.^[4]

Due to the rise of offshore drilling, mining and the limitations of fisheries off the continental shelf, the United Nations Convention on the Law of the Sea (UNCLOS) was established. The edge of the continental margin is one criterion for the boundary of the internationally recognized claims to underwater resource by countries in the definition of the "continental shelf" past the UNCLOS (although in the UN definition the "legal continental shelf" may extend beyond the geomorphological continental shelf and vice versa).^[2] Such resources include fishing grounds, oil and gas accumulations, sand, gravel, and some heavy minerals in the shallower areas of the margin. Metallic minerals resources are thought to too exist associated with certain active margins, and of great value.^[3]

Come across as well [edit]

Continent-bounding main boundary
Convergent boundary
Passive margin

References [edit]

^ ^a ^b ^c ^d Five., Thurman, Harold (2014-01-01). Essentials of Oceanography. Pearson. ISBN9780321668127. OCLC 815043823.
^ ^a ^b Melt, P.J.; Carleton, Chris (2000). Continental shelf limits : the scientific and legal interface. Oxford: Oxford Academy Press. ISBN0-nineteen-511782-4.
^ ^a ^b ^c ^d ^e ^f Board., National Research Council (U.S.). Body of water Sciences (1979-01-01). Continental margins : geological and geophysical enquiry needs and problems. National Academy of Sciences. ISBN0309027934.
^ ^a ^b ^c ^d ^e ^f Grotzinger, Jordan (2007). Agreement Earth . Due west H Freeman. pp. 491–496. ISBN978-0716766827.
^ ^a ^b Gulicher, Andre (1958). Coastal and Submarine Morphology. Great Great britain: Butler & Tanner Ltd. pp. 205–215.
^ "Active and passive continental margins".