Downward recycling of a lithospheric plate into the mantle. A sufficiently cold, dense slab can provide slab pull, while bending and friction resist motion. The resulting material and volatile recycling connects plate tectonics with volcanism and long-term climate.
Release of water-rich fluid by reactions that destabilize hydrated minerals in a descending slab. It can promote flux melting of the mantle wedge and contribute to dehydration embrittlement. The released water is not evidence that the whole slab has melted.
The effect of slab-induced mantle flow, pressure and traction on the motion of neighbouring plates and their boundary. It is part of the coupled response to a sinking slab, rather than an unrelated energy source that can always be added independently to slab pull.
Migration of a subduction trench relative to the surrounding mantle as a slab retreats; the associated mantle flow can advect thermal anomalies.
Partial melting of material within a descending slab, distinct from flux melting of the mantle wedge by fluids released from the slab.
A proposed buoyant ascent of mixed sedimentary, crustal and hydrated mantle material from an interface region into the mantle wedge.
Mechanical addition of solid slices beneath the overriding plate. Distinct from crystallization of new magma by magmatic underplating.
Establishment of sustained downward plate motion, distinct from its later continuation under existing plate forces.
The region containing a descending plate, its interface and the associated upper-plate and mantle wedge system.
A coupled phenomenon in which transient slow fault slip occurs with low-frequency seismic tremor, often near the downdip transition from locked to steadily creeping parts of a megathrust. Geodetic displacement and seismic signals provide complementary observations. Along-strike differences in recurrence, migration and cumulative slip help characterize subduction zone segmentation; tremor counts alone do not uniquely give fault slip or coupling.
Along-strike changes in the structure, deformation, coupling or thermal state of a subduction zone. Segments inferred from megathrust locking, episodic tremor and slip, past earthquake ruptures, slab dip and seismic tomography need not have identical boundaries. A common spatial pattern can motivate a physical hypothesis, but does not alone prove a persistent rupture barrier or identify a unique cause.
The subduction zone beneath the Pacific Northwest of North America, where the Juan de Fuca Plate and adjacent oceanic plates descend beneath the North American Plate.
An accreted basaltic terrane forming important parts of the forearc basement in the Pacific Northwest. Spatial variations in its thickness, stiffness and permeability can affect the interpretation of gravity anomalies and the fluid/stress environment above the megathrust. A proposed relation to central Cascadia creep uses gravity, geodetic and paleoseismic observations, rather than lithology alone.[ref]
Central Cascadia subduction zone creep by Gina M. Schmalzle and others. Discussion and conclusions, Siletzia and fluid-pressure interpretation
The wedge-shaped mantle above a descending slab, whose circulation and chemical modification influence arc magmas.
The upper-plate region between the subduction trench and volcanic arc.
A wedge of material transferred from the incoming plate to the overriding plate by offscraping or underplating.
The mantle of the overriding plate beneath the forearc, potentially hydrated by slab-derived fluids.
The local angle of a descending slab relative to a horizontal surface; it can change with depth and along the margin.
A regime in which an initially descending slab becomes nearly horizontal beneath the overriding plate for a substantial inland distance before descending again. It can narrow or eliminate a hot mantle wedge, shift deformation inland and coincide with a volcanic gap. Incoming buoyant crust, hydration, upper-plate motion and mantle forces can all contribute; association with an oceanic ridge does not isolate one cause.
Net gravitational effect of thermal and compositional density contrasts between a slab and its surroundings, including phase changes.
The upper plate above a subducting plate. Its motion determines the normal velocity of a non-rolling-back trench in the idealized triple-junction compatibility construction.
A convergent margin where one plate descends beneath another. In a simple junction-kinematic model the trench normal motion is tied to the overriding plate; rollback or distributed deformation can modify that rule.
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Subduction is a geological process that occurs at convergent plate boundaries, where one tectonic plate moves under another and sinks into the Earth’s mantle. This typically happens when an oceanic plate, which is denser, collides with a continental plate or another oceanic plate. The descending plate creates a subduction zone, characterized by deep ocean trenches, volcanic arcs, and earthquake activity.