The inner wall of the trench toward the arc, has a very complex structure called the subduction complex where underthrusting adds many slices of ocean floor rocks to the inner wall of the trench. This magma makes it way to the surface to erupt in a chain of volcanoes called an island arc which forms in the over riding plate.
Often andesitic magma forms within the heated lithosphere down in the subduction zone. The deepest ocean in the world is found along trenches. The subducting lithosphere is bent downward to form a very deep depression in the ocean floor called a trench. When two oceanic lithospheres collide, one runs over the other which causes the latter to sink into the mantle along a zone called a subduction zone.
Ocean-Ocean Convergence - Oceanic lithosphere is relatively dense and can easily sink into the Earth's mantle. There are three major types of convergence zones. The type of tectonic features which form depend on the types of lithosphere involved in the collision. Plate Interaction - The plates interact with each other along three types of plate boundaries:Ĭonvergent Plate Boundaries - these boundaries are found where two plates run into each other just like two cars hitting head on in an accident. The dozen major plates are as follows:Įurasian - Australian-Indian
The word, tectonic, refers to the deformation of the Lithosphere as a consequence of plate interaction. Each type of interaction causes a characteristic set of earth structures or "Tectonic" features. Because of the motion of the plates they can collide, pull apart, or scrap against each other. Plate Tectonics - is the paradigm that the Earth's lithosphere is divided into a dozen major plates which slide over the asthenosphere in various directions.
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