Continental Rise Definition
Continental Rise meaning will seem to be very simple once you go through the given definition. There's a surprising place where possibly half of the world's sediments are settling. These materials that collapse by eroding and then transported by rivers and streams aren't always ending up in stream beds, river deltas or flood zones. Rather, many of them finish up in a place that's not on land at all. These sediments are sent to the continental rise below the ocean, where enough of them settle that it induces a distinctive mound that encompasses the world's continental edges.
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Continental Margin
Beginning from the continental edge, where dry land turns to ocean, the first of three parts of the region known as the continental margin, is the shallow, gentle descent of the continental shelf. This area can be as tapered as 15 miles and as wide as 228 miles.
Think of it as an elongated hill of sediments deep beneath the ocean's surface. The continental rise is also part of a bigger region known as the continental margin.
After the continental shelf, you would be in for a trace of a fall. Next is the steep cliff of the continental slope. The transformation between the continental shelf and the continental slope is what we call the continental shelf break. It's not really an exact spot, but more like a region where the continental margin moves from the less steep continental shelf to the much steeper continental slope. The continental slope is nowhere near to smooth and rather, is marked by innumerable, submarine canyons that run perpendicular to the continental slope.
Ultimately, after the continental slope, you would get access to the third part of the continental margin. While it's greater level than the continental slope, it's not as very smooth as what follows – the expansive ocean floor.
Difference Between Continental Slope and Continental Rise
Continental slope is a slope with a steep or gentle gradient. It is a sectional division after the continental shelf. On the other hand, Continental rise is simply the deposition of debris or sediments brought by the currents.
Animals that Live in the Continental Rise
Talking about the continental rise marine life, we can find animals like Crab, cod, tuna, lobster, sole, halibut, mackerel and Dungeness in the continental rise depth. Permanent rock fixtures are home to anemones, clams, corals, mussels, oysters, scallops, and sponges. Huge sea animals such as whales and sea turtles can be found in continental shelf areas as they follow migration routes.
The Geologic Basis For the Continental Rise
The concept of the continental rise appeared across the classic passive margin area of the western North Atlantic. There the continental rise envelops the ocean crust fringing the fractured and the faulted continental margin. It is the location where the sediment discards from the continent into the deep sea deposits. Along active margins where ocean crust is being subducted under the continental crust, the margin is often manifested by an ocean trench; there is no continental rise. However in some regions where there is a massive thickness of sediment on the ocean floor making way to the subduction zone, or where the supply of sediment from the continent into the subduction zone totally brims up the trench, a narrow continental rise may occur.
Fun Facts
The continental rise is the gently disposed slope between the substructure of the continental slope and the deep ocean floor.
The expression “continental rise” was initially used by Maurice Ewing and Bruce Heezen in their narrative of the effects of the 1929 Grand Banks earthquake.
It was formally described by Heezen et al. in GSA Special Paper 65 in 1959.
“Since the continental slope is restricted to gradients higher than 1:40, the lower portion of the continental margin is split into a separate province, the continental rise”.
In many regions, domestic morphologic characteristics interfere with the usual slopes such that neither the upper or lower limits of the continental rise are well described.
FAQs on Continental Rise
1. What is a continental rise in geography?
A continental rise is a major underwater feature of the ocean floor, located between the steep continental slope and the vast, flat abyssal plain. It is a wide, gently sloping region formed by the accumulation of thick sediments, such as sand, mud, and debris, that have moved down from the continental shelf and slope over millions of years.
2. How is a continental rise formed?
A continental rise is formed primarily through the process of sediment deposition. Sediments are transported from the continents down the steep continental slope. This occurs mainly through two processes:
- Turbidity currents: Fast-moving, dense underwater avalanches of sand and mud.
- Contour currents: Ocean currents that flow parallel to the continental margin, distributing the sediments.
3. What is the difference between the continental slope and the continental rise?
The main difference lies in their gradient and formation. The continental slope is a relatively steep zone that marks the true edge of the continent, connecting the shallow continental shelf to the deep ocean basin. In contrast, the continental rise is a much more gently sloping wedge of accumulated sediment that lies at the base of the slope. The slope is a zone of transport, while the rise is a zone of deposition.
4. What are the key characteristics of a continental rise?
The defining characteristics of a continental rise include:
- Gentle Gradient: It has a very low slope, typically between 0.5 and 1.0 degrees, making it almost flat.
- Thick Sediments: It is composed of extremely thick layers of sediment, sometimes several kilometres deep.
- Submarine Fans: It often features large, fan-shaped deposits created by turbidity currents exiting submarine canyons.
- Location: It is found at the base of the continental slope, forming a transition to the abyssal plain, at depths ranging from 1,500 to 5,000 metres.
5. Where are some real-world examples of continental rises located?
Continental rises are prominent features along passive continental margins. A classic example is the rise found off the eastern coast of North America in the Atlantic Ocean. Another massive example is in the Bay of Bengal, where the enormous sediment load from the Ganges and Brahmaputra rivers has formed one of the world's largest deep-sea fans, contributing to an extensive continental rise.
6. Why is the continental rise considered a 'sediment graveyard'?
This term aptly describes its function as the final destination for vast quantities of sediment eroded from the continents. Rivers carry this material to the sea, where it is transported down the continental slope. Due to the sharp decrease in gradient at the base of the slope, the transport energy of currents drops significantly, forcing the sediment to be permanently deposited. This makes the continental rise a massive, long-term accumulation zone, or 'graveyard', for terrestrial materials.
7. What is the geological and economic importance of the continental rise?
Geologically, the continental rise holds a detailed record of a continent's erosional history and past climate changes, preserved within its sediment layers. Economically, these thick sedimentary deposits are highly significant. The organic matter buried within them, when subjected to immense pressure and heat over geological time, can transform into vast reserves of oil and natural gas.
8. Do continental rises form at active continental margins?
Generally, no. Continental rises are characteristic features of passive continental margins (e.g., the Atlantic coast), where there is no active plate boundary. At active continental margins (e.g., the Pacific coast of South America), there is typically a deep-sea trench instead of a rise. The tectonic process of subduction, where one plate slides under another, consumes the oceanic crust and any accumulated sediment, which prevents a rise from forming.
