A convergent boundary (also known as a destructive boundary) is an area on Earth where two or more lithospheric plates collide. One plate eventually slides beneath the other, a process known as subduction. The subduction zone can be defined by a plane where many earthquakes occur, called the Wadati–Benioff zone. These collisions happen on scales of millions to tens of millions of years and can lead to volcanism, earthquakes, orogenesis, destruction of lithosphere, and deformation. Convergent boundaries occur between oceanic-oceanic lithosphere, oceanic-continental lithosphere, and continental-continental lithosphere. The geologic features related to convergent boundaries vary depending on crust types.

Plate tectonics is driven by convection cells in the mantle. Convection cells are the result of heat generated by the radioactive decay of elements in the mantle escaping to the surface and the return of cool materials from the surface to the mantle. These convection cells bring hot mantle material to the surface along spreading centers creating new crust. As this new crust is pushed away from the spreading center by the formation of newer crust, it cools, thins, and becomes denser. Subduction begins when this dense crust converges with a less dense crust. The force of gravity helps drive the subducting slab into the mantle. As the relatively cool subducting slab sinks deeper into the mantle, it is heated, causing hydrous minerals to break down. This releases water into the hotter asthenosphere, which leads to partial melting of the asthenosphere and volcanism. Both dehydration and partial melting occur along the 1,000 °C (1,830 °F) isotherm, generally at depths of 65 to 130 km (40 to 81 mi).

Some lithospheric plates consist of both continental and oceanic lithosphere. In some instances, initial convergence with another plate will destroy oceanic lithosphere, leading to convergence of two continental plates. Neither continental plate will subduct. It is likely that the plate may break along the boundary of continental and oceanic crust. Seismic tomography reveals pieces of lithosphere that have broken off during convergence.

Subduction zones are areas where one lithospheric plate slides beneath another at a convergent boundary due to lithospheric differences. These plates dip at an average of 45° but can vary. Subduction zones are often marked by an abundance of earthquakes, the result of internal deformation of the plate, convergence with the opposing plate, and bending at the oceanic trench. Earthquakes have been detected to a depth of 670 km (416 mi). The relatively cold and dense subducting plates are pulled into the mantle and help drive mantle convection.

In collisions between two oceanic plates, the cooler, denser oceanic lithosphere sinks beneath the warmer, less dense oceanic lithosphere. As the slab sinks deeper into the mantle, it releases water from dehydration of hydrous minerals in the oceanic crust. This water reduces the melting temperature of rocks in the asthenosphere and causes partial melting. Partial melt will travel up through the asthenosphere, eventually, reach the surface, and form volcanic island arcs.^{[citation needed]}

When oceanic lithosphere and continental lithosphere collide, the dense oceanic lithosphere subducts beneath the less dense continental lithosphere. An accretionary wedge forms on the continental crust as deep-sea sediments and oceanic crust are scraped from the oceanic plate. Volcanic arcs form on continental lithosphere as the result of partial melting due to dehydration of the hydrous minerals of the subducting slab.^{[citation needed]}

Some lithospheric plates consist of both continental and oceanic crust. Subduction initiates as oceanic lithosphere slides beneath continental crust. As the oceanic lithosphere subducts to greater depths, the attached continental crust is pulled closer to the subduction zone. Once the continental lithosphere reaches the subduction zone, subduction processes are altered, since continental lithosphere is more buoyant and resists subduction beneath other continental lithosphere. A small portion of the continental crust may be subducted until the slab breaks, allowing the oceanic lithosphere to continue subducting, hot asthenosphere to rise and fill the void, and the continental lithosphere to rebound. Evidence of this continental rebound includes ultrahigh pressure metamorphic rocks, which form at depths of 90 to 125 km (56 to 78 mi), that are exposed at the surface. Seismic records have been used to map the torn slabs beneath the Caucasus continental – continental convergence zone, and seismic tomography has mapped detached slabs beneath the Tethyan suture zone (the Alps – Zagros – Himalaya mountain belt).

The oceanic crust contains hydrated minerals such as the amphibole and mica groups. During subduction, oceanic lithosphere is heated and metamorphosed, causing breakdown of these hydrous minerals, which releases water into the asthenosphere. The release of water into the asthenosphere leads to partial melting. Partial melting allows the rise of more buoyant, hot material and can lead to volcanism at the surface and emplacement of plutons in the subsurface. These processes which generate magma are not entirely understood.