- #CONTINENTAL CONTINENTAL CONVERGENT BOUNDARY CRACKED#
- #CONTINENTAL CONTINENTAL CONVERGENT BOUNDARY SERIES#
The magma produced adjacent to the subduction zone rises to the base of the continental crust and leads to partial melting of the crustal rock. Sediment that has accumulated on the seafloor is thrust up into an accretionary wedge, and compression leads to thrusting within the continental plate (Figure 4.6.2). Earthquakes occur relatively deep below the seafloor, where the subducting crust moves against the overriding crust.įigure 4.6.1 A trench and volcanic island formed from an ocean-ocean convergent zone (Steven Earle, “Physical Geology”).Įxamples of ocean-ocean convergent zones are subduction of the Pacific Plate south of Alaska (creating the Aleutian Islands) and under the Philippine Plate, where it creates the Marianas Trench, the deepest part of the ocean.Īt an ocean-continent convergent boundary, the denser oceanic plate is pushed under the less dense continental plate in the same manner as at an ocean-ocean boundary. A mature island arc develops into a chain of relatively large islands (such as Japan or Indonesia) as more and more volcanic material is extruded and sedimentary rocks accumulate around the islands.
The magma, which is lighter than the surrounding mantle material, rises through the mantle and the overlying oceanic crust to the ocean floor where it creates a chain of volcanic islands known as an island arc. It mixes with the overlying mantle, and the addition of water to the hot mantle lowers the crust’s melting point and leads to the formation of magma (flux melting). The significant volume of water within the subducting material is released as the subducting crust is heated. The subducted lithosphere descends into the hot mantle at a relatively shallow angle close to the subduction zone, but at steeper angles farther down (up to about 45°). There is commonly an ocean trench along the boundary as the crust bends downwards. Often it is the older and colder plate that is denser and subducts beneath the younger and warmer plate. The types are ocean-ocean, ocean-continent, and continent-continent.Īt an ocean-ocean convergent boundary, one of the plates (oceanic crust and lithospheric mantle) is pushed, or subducted, under the other (Figure 4.6.1).
#CONTINENTAL CONTINENTAL CONVERGENT BOUNDARY CRACKED#
In contrast to convergent and divergent boundaries, crust is cracked and broken at transform margins, but is not created or destroyed.Modified from "Physical Geology" by Steven Earle*Ĭonvergent boundaries, where two plates are moving toward each other, are of three types, depending on the type of crust present on either side of the boundary - oceanic or continental. Earthquakes are common along these faults. Rocks that line the boundary are pulverized as the plates grind along, creating a linear fault valley or undersea canyon.
Natural or human-made structures that cross a transform boundary are offset - split into pieces and carried in opposite directions. One of the most famous transform plate boundaries occurs at the San Andreas fault zone, which extends underwater. Two plates sliding past each other forms a transform plate boundary. Thus, at convergent boundaries, continental crust is created and oceanic crust is destroyed. Magma rises into and through the other plate, solidifying into granite, the rock that makes up the continents. The Pacific Ring of Fire is an example of a convergent plate boundary.Īt convergent plate boundaries, oceanic crust is often forced down into the mantle where it begins to melt. A chain of volcanoes often forms parallel to convergent plate boundaries and powerful earthquakes are common along these boundaries. The impact of the colliding plates can cause the edges of one or both plates to buckle up into a mountain ranges or one of the plates may bend down into a deep seafloor trench. When two plates come together, it is known as a convergent boundary. The Mid-Atlantic Ridge is an example of divergent plate boundaries. Along these boundaries, earthquakes are common and magma (molten rock) rises from the Earth’s mantle to the surface, solidifying to create new oceanic crust.
#CONTINENTAL CONTINENTAL CONVERGENT BOUNDARY SERIES#
The Earth’s lithosphere, which includes the crust and upper mantle, is made up of a series of pieces, or tectonic plates, that move slowly over time.Ī divergent boundary occurs when two tectonic plates move away from each other. This image shows the three main types of plate boundaries: divergent, convergent, and transform.
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