oceaniccontinental

Oceanic-continental convergence is a tectonic boundary where an oceanic plate collides with a continental plate. Because oceanic crust is denser, it subducts beneath the lighter continental crust, forming a deep ocean trench and a Wadati-Benioff seismic zone at depth. Subduction drives melting in the mantle wedge, producing magmas that rise to the surface to form a continental volcanic arc.

Geologic features commonly associated with this convergence include a coastal trench, an arc of active volcanoes on the continent, an accretionary wedge of sediments scraped from the subducting slab, and significant crustal deformation that uplifts mountain belts. Earthquakes are frequent, ranging from shallow events near the trench to large megathrust earthquakes capable of tsunamis.

Notable systems include the Nazca Plate subducting beneath South America, which creates the Andes and the Peru-Chile Trench; the Juan de Fuca Plate under western North America, producing the Cascades; and subduction zones around Japan and the Indonesian region. Oceanic-continental boundaries differ from oceanic-oceanic subduction, which forms island arcs, and from continental-continental collision, which mainly thickens crust without sustained subduction.

Over geological timescales, oceanic-continental convergence contributes to continental growth and regional seismic and volcanic hazard, as well as ore formation and hydrothermal activity along continental margins.