Convergent plate boundary (slab pull at 2–11 cm/yr; dip 25°–75°)
typical scale
55,000 km cumulative global length; trenches up to 11 km deep, earthquakes to 700 km depth
characteristic lithology
Blueschist and eclogite slab facies; calc-alkaline andesite, diorite, and granite arcs
examples
Mariana Trench, Cascadia Subduction Zone, Peru–Chile (Andean) Trench, Sunda Arc
Core Principles & Analysis
Driven primarily by the negative buoyancy ('slab pull') of cold, dense oceanic lithosphere sinking into the asthenosphere, subduction zones recycle oceanic plates along 55,000 km of convergent margins and trace inclined Wadati–Benioff earthquake zones down to 700 km depth.
As the descending basaltic slab transforms under high pressure into dense eclogite near 100 km depth, hydrous minerals (such as serpentine) release supercritical water into the overlying mantle wedge, triggering flux melting that feeds explosive volcanic arcs.
Subduction interfaces generate Earth's most powerful megathrust earthquakes and tsunamis (including the 1960 M9.5 Valdivia and 2011 M9.1 Tōhoku earthquakes) and have generated the majority of Earth's buoyant continental crust.