Chapter 21: Convergent Plate Boundaries

Folded mountain belt

a long, linear zone of Earth's crust where rocks have been intensely deformed by horizontal stresses and generally intruded by igneous rocks. The great folded mountains of the world - Appalachians, Himalayas, Rockies, Alps - are believed to have been formed at convergent plate margins

Trench

a narrow, elongate depression of the deep-ocean floor oriented parallel to the trend of a continent or an island arc

Convergent plate boundary

a plate boundary at which plates collide. Convergent plate boundaries are sites of considerable geologic activity and are characterized by volcanism, earthquakes, and crustal deformation.

Ocean-continent convergence

a subduction zone where oceanic and continental plates abut. the plate with the less-dense continental crust always resists subduction into the dense mantle and overrides the oceanic plate, often deforming into a folded mountain belt

Ocean-ocean convergence

a subduction zone where two adjoining oceanic plates collide, with one thrust under the other i.e. Japan, indonesia, etc

Forearc ridge

a topographical feature between a trench and an associated volcanic arc, underlain by the accretionary wedge of sediment scraped off the seafloor during subduction

Accretionary wedge

a wedge-shaped body of faulted and folded material scraped off subducting oceanic crust and added to an island arc or continental margin at a subduction zone

Volcanic arc

an arcuate chain of volcanoes on the margin of an overriding plate at a convergent boundary with a subduction zone.

Subduction zone

an elongate zone in which one lithospheric plate descends beneath another. A subduction zone is typically marked by an oceanic trench, lines of volcanoes, and crustal deformation associated with mountain building.

Continent-continent convergence

occurs when continents on two different tectonic plates collide. The Himalaya mountain belt is produced by this process

Types of convergent boundaries

ocean-continent ocean-ocean continent-continent

Back-arc

the area behind a subduction-related volcanic arc where folds and faults form. Most are extending.

Continental accretion

the growth of continents by incorporation of deformed sediments, arc magmas, and accreted terranes along their margins