The continental margins consist of three portions: (1) the continental shelf which has shallow water depths rarely deeper than 650 ft) and extends seaward from the shoreline to distances ranging from 12.3 miles to 249 miles, (2) the continental slope where the bottom drops off to depths of up to 3.1 miles, and (3) the continental rise which dips very shallowly seaward from the base of the continental slope and is in part composed of down-washed sediments deposited at the base of the slope.
What is the continental margin made of?
The continental margin is that part of the ocean floor at the edges of the continents and major islands where, just beyond the shoreline, it tapers gently into the deep sea. The continental margin is made up of the continental shelf, the continental slope, and the continental rise.
What are the continental margins on the trailing side of tectonic plates?
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.
How much of the ocean is consumed by the continental margins?
The Continental margins consume about 28% of the area of the ocean. 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.
Why is the continental margin important to humans?
The continental margin is the ocean area most easily reached by humans and so it has an important effect on human life. About 90 percent of the world’s marine food resources come from the waters over the continental shelves. Most of those resources consist of fish.
What are continental margins made of?
Continental margins are made of thick accumulations of sedimentary rock, the type of rock in which oil and gas generally occur.
What are three major features of a passive continental margin?
The features comprising passive continental margins include the continental shelf (the flooded extension of the continent), the continental slope (has the steepest slope), and the continental rise.
What are main features of continental margins?
Major Continental Margin FeaturesContinental shelf. This is very shallow water, and underlain by continental crust. ... Continental slope. This is much steeper than the shelf, usually about 3° but ranging from 1-10°. ... Continental rise. ... Abyssal plains.
What are three major features of a passive continental margin quizlet?
A passive continental margin is tectonically inactive and features a continental shelf, a continental slope, and a continental rise (from land toward the sea); An active continental margin is located along a convergent plate boundary, has a deep-ocean trench where subduction takes place, and may have evidence of an ...
What is the continental margin quizlet?
Continental margin. the zone of the ocean floor that separates the thin oceanic crust from thick continental crust. Together, the continental shelf, continental slope, and continental rise are called the continental margin. continental rise. an underwater feature found between the continental slope and the abyssal ...
What is not part of the continental margin?
Which of the following is NOT part of the continental margin? coral reefs surrounding a lagoon. You just studied 65 terms!
Which of the following are components of an active continental margin?
Active continental margins are those that are tectonically active, such as along much of the Pacific coast. Active margins are marked by earthquakes, volcanoes, and mountain belts. Unlike passive margins, they lack a continental rise and abyssal plain.
How is active continental margin formed?
An active continental margin is found on the leading edge of the continent where it is crashing into an oceanic plate. An excellent example is the west coast of South America. Active margins are commonly the sites of tectonic activity: earthquakes, volcanoes, mountain building, and the formation of new igneous rock.
How many types of continental margins are there?
Continental margins can be fundamentally divided into three basic types worldwide. These are
What is the result of convergent continental margins?
The Appalachian Mountains in eastern United States and the Ural Mountains in Russia are examples of the result of convergent continental margins where sediments accumulated and were then uplifted in an orogenic period to form the stable mountains that are eroding today and furnishing sediments to the low land areas on both sides of the mountains.
What are the characteristics of volcanic rock in the Cordilleran continental margin volcanic arc?
The characteristics of volcanic rock in the Cordilleran continental margin volcanic arc are similar to those in the west Pacific intraoceanic arc; that is, dominated by intermediate andesite, the volcanic rock has apparent horizontal zonality in the direction from trench to land.
What is the Cordilleran volcanic arc?
The Cordilleran continental margin volcanic arc mainly refers to the Cordilleran mountain range zone in South America, and it, together with the west Pacific volcanic arc zone, composes the circum-Pacific volcanic circle, which has a total length of more than 40,000 km. There are 30 active volcanoes in the south section of the Andes, the Cordillera mountain system, and 16 active volcanoes in the north section. The Llullaillaco volcano in the middle with an altitude of 6723 m is the highest active volcano in the world. The characteristics of volcanic rock in the Cordilleran continental margin volcanic arc are similar to those in the west Pacific intraoceanic arc; that is, dominated by intermediate andesite, the volcanic rock has apparent horizontal zonality in the direction from trench to land. The main eruption mode is centered eruption.
How far does the International Law of the Sea extend?
In some instances the International Law of the Sea provides that jurisdiction over natural resources extends beyond the 200-nautical mile (230-mile) boundary to the edge of the geological continental margin based on geological factors such as sediment thickness and water depth.
How are transform margins formed?
Transform continental margins (sheared margins) are formed due to lateral plate movements or shearing motions during the continental breakup process in the divergent margin setting. Identifying this category of margins is also in a way important, as they represent an original offset in the line of continental breakup and can normally be traced laterally into an oceanic fracture zone ( Bird, 2001 ). Further, transform margins are also noticed along the Pacific type continental margins.
What are the Pacific type margins?
The active continental margins referred as the Pacific-type margins are the zones of seismically active convergent plate boundaries. These are characterized by subduction zones formed under variety of settings such as oceanic–oceanic, oceanic–continental, etc. and are mostly observed along the periphery of the Pacific Ocean.
Why is the continental margin shaped?
The present shape of a continental margin may be due to several influences. Movement of Earth’s crust may have given it a folded appearance where the sea floor cracked and was pushed underneath the margin. Huge boulders and rocks may indicate that a glacier once moved across the region. The presence of a river may mean a larger quantity of sediment
How is the continental margin determined?
The general shape of the continental margin is usually determined by the shape of the coastline from which it extends. If it extends from a plain, then the margin will be broad and level. If it extends from a mountainous coast, then it will be steep and rocky. Steep cliffs that may have been formed by wave action when the level of the sea was lower may now be submerged and form part of the margin.
How did the continental margin of the United States form?
The continental margin off the northwestern coast of the United States was partly formed by a dam of rock thrust up by earthquake action about 25 million years ago. Where the dam breaks the surface of the water, it forms the Farallon Islands off San Francisco. The shelf is so narrow here—only about 1 mile (1.6 kilometers) wide—that the heads of many submarine canyons reach almost to the shoreline. Large quantities of sand from the beaches are carried by currents down the canyon walls.
How wide is the continental shelf?
The continental shelfbegins at the shoreline. It is flat and its width varies. For example, off the Arcticcoast of Siberia it is 800 miles (1,280 kilometers) wide. Rich sediment (particles of soil and decaying matter) from rivers that flow to the sea filters down to the shelf. Over time, deposits of these sediments may become many thousands of feet (meters) thick. At its deepest points, the continental shelf is usually less than 660 feet (200 meters) below sea level(the level surface of the sea). Although the continental shelf is easier to explore than deeper areas of the ocean, there is still much to learn.
When did the continental shelf rise?
About 20 million years ago , when the sea levelwas at its lowest, the area that now makes up the continental shelves was above water. Forests may have grown there and it may have been home to many animals. Over millions of years, rain, wind, and wave action eroded (wore away) the shelf surface, and rivers and glaciers flowed across it. Gradually, sediments from the shelves were washed into the water. Later, as the glaciers melted, the sea level rose and covered the shelves so that the entire continental margin was under water.
Where are active margins found?
It is constantly changing due to the continuous earthquake and volcanic activity. Active margins are often found in the Pacific Ocean, such as those along the west coast of South America. They are narrow and often drop sharply into a deep trench (steep valley).
What is subduction zone?
Subduction zone:Area where pressure forces the seafloor down and under the continental margin, often causing the formation of a deep ocean trench.
Formation of The Continental Margins
The Water Column
Geography of Continental Margins
Plant Life
Animal Life
Human Life
The Food Web
Spotlight on Continental Margins
- Queensland, Australia and The Great Barrier Reef
The Great Barrier Reef, the longest structure in the world created by living organisms, consists of slightly fewer than 3,000 smaller reefs joined together. It covers approximately 132,974 square miles (344,400 square kilometers), which is almost the size of the state of Kansas. At least 500,… - Northwestern Australia and Southeast Asia
On the continental shelf off the coast of northwestern Australia are the islands of Sumatra, Java, Borneo, and the Malaysian Peninsula, the most volcanic islands in the world. Other islands, including New Guinea, New Zealand, and the Philippines, are formed from part of the shelf. Sout…
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