Continental Margins
13 likes5,472 views
The document discusses continental margins, differentiating between passive and active types. Passive margins are geologically stable regions that include the continental shelf, slope, and rise, while active margins face geological activity such as earthquakes and volcanic activity. It also describes the characteristics of features such as submarine canyons, turbidity currents, abyssal fans, and abyssal plains, highlighting their formation processes and sedimentary environments.
Continental Margins
- 1. CONTINENTAL MARGINS VIMAL RAJ 1st MSc APPLIED GEOLOGY UNIVERSITY OF CALICUT
- 2. CONTINENTAL MARGINS CONTINENTAL SHELF CONTINENTAL SLOPE CONTINENTAL RISE
- 3. PASSIVE CONTINENTAL MARGINS A passive continental margin includes a continental shelf, continental slope, and continental rise, and generally extends down to an abyssal plain at a depth of about 5 kilometers (3.1 miles). It is called a passive margin , because it usually develops on geologically quiet coasts that lack earthquakes, volcanoes, and young mountain belts. Passive margins are found on the edges of most landmasses bordering the Atlantic Ocean. They also border most parts of the Arctic and Indian Oceans and a few parts of the Pacific Ocean
- 4. ACTIVE CONTINENTAL MARGINS An active continental margin, typically characterized by earthquakes and a young mountain belt and volcanoes on land, consists of a continental shelf, a continental slope, and an oceanic trench. An active margin usually lacks a continental rise and an abyssal plain and is associated with convergent plate boundaries.
- 6. CONTINENTAL SHELF A shallow submarine platform at the edge of a continent, inclines very gently seaward, generally at an angle of 0.1°. Continental shelves vary in width. Eg: on the pacific coast of north america, the shelf is only a few kilometers Wide, but off newfoundland in the atlantic ocean, it is about 500 kilometers (310 miles) wide. Continental shelves are topographic features, defined by their depth, flatness, and gentle seaward tilt. Their geologic origin varies from place to place and is related to plate tectonics The continental shelves of the world are usually covered with relatively young sediment, in most cases derived from land. The sediment is usually sand near shore, where the bottom is shallow and influenced by wave action.
- 7. CONTINENTAL SLOPE Is a relatively steep slope that extends from a depth of 100 to 200 meters at the edge of the continental shelf down to oceanic depths. The average angle of slope for a continental slope is 4° to 5°, although locally, some parts are much steeper. 8.5 per of the ocean floor is coverd by the continental slope-rise system. Continental slopes are identified by numerous sub marine canyons and mounds.The predominant sedimants of continental slopes are muds;there are smaller amount of sediments of sand or gravel. Continental slopes are temporary depositional sites of sediments It extends from the shelf break to water depth typically of around 3000- 4000 m
- 9. SUBMARINE CANYONS Submarine canyon is steep-sided, V-shaped valley that is formed at outer edge of continental shelf and continue across the slope. submarine canyons must be formed underwater and associated with a submarine mechanism.
- 10. TURBIDITY CURRENTS are created when loose, wet sediment tumbles down the slope resembles a submarine landslide. The movement can be caused by an earthquake or simply by gravity on the slope when sediment overloads. A turbidity current can reach a speed greater than 100 kilometers per hour and a distance up to 700 kilometers. With this speed and range turbidity current has tremendous erosive power. Turbidity currents slow down once they reach the sea floor and the sediment starts to accumulate to form the ABYSSAL FAN.
- 11. ABYSSAL FANS are accumulations of sediment deposited at the termini of land-to-deep-sea sediment-routing systems. Similar to alluvial fans, Abyssal fans are gravity feed debris flows down the continental slope. Abyssal fans are deposited at their termini and generally exhibit radial-, cone-, or fan-like morphologies in map view across the seafloor. Moreover, during the course of basin evolution, abyssal fans can be uplifted by tectonic forces and subsequently eroded and re-deposited.
- 12. CONTINENTAL RISE Along the base of many parts of the continental slope lies the continental rise, a wedge of sediment that extends from the lower part of the continental slope to the deep-sea floor. The continental rise, which slopes at about 0.5°, more gently than the continental slope, typically ends in a flat abyssal plain at a depth of about 5 kilometers. The rise rests upon oceanic crust. The environment in the continental rise is quite and unique.
- 13. At the bottom of continental slope ,one will find the continental rise ,an under water hill composed of tons of accumulated sediments. the general slope of the continental rise is between 0.5 and 1.0 degrees. It streches the abyssl plain ,an extremely deep and flat area of the sea floor. Continental rise form as a result of three sedimentary process MASS WASTING THE DEPOSITION FROM THE CONTOUR CURRENTS VERTICAL SETLING OF CLASTIC AND BIOGENIC PARTICLES
- 14. ABYSSAL PLAINS are very flat regions usually found at the base of the continental rise. Seismic profiling has shown that abyssal plains are formed of horizontal layers of sediment. The gradual deposition of sediment buried an older, more rugged topography that can be seen on seismic profiler records as a rock basement beneath the sediment layers .Samples of abyssal plain sediment show that it is derived from land. Graded bedding within sediment layers suggests deposition by turbidity currents.