Subduction Zones

Abstract

Subduction zones are where sediments, oceanic crust, and mantle lithosphere return to and reequilibrate with Earth's mantle. Subduction zones are interior expressions of Earth's 55,000 km of convergent plate margins and are the geodynamic system that builds island arcs. Excess density of the mantle lithosphere in subduction zones provides most of the power needed to move the plates while inducing convection in the overriding mantle wedge. Asthenospheric mantle sucked toward the trench by the sinking slab interacts with water and incompatible elements rising from the sinking plate, and this interaction causes the mantle to melt. These melts rise vertically through downwelling mantle to erupt at arc volcanoes. Subduction zones are thus interior Earth systems of unparalleled scale and complexity. Subduction zone igneous activity formed most ore deposits and continental crust, and earthquakes caused by the downgoing plate present a growing hazard to society. This overview summarizes our present understanding of subduction zones, using perspectives of the incoming plate, downgoing plate, mantle wedge, and arc‐trench complex. Understanding the operation of subduction zones stands as one of the great challenges facing the Earth sciences in the 21st century and will require the efforts of global interdisciplinary teams.

Coastal tectonics on the eastern margin of the Pacific Rim: late Quaternary sea-level history and uplift rates, Channel Islands National Park, California, USA

“…In this continuum, lowangle subduction zones, with strongly coupled plates, characterize one end-member (the "Chilean" type), and high-angle subduction zones, with weakly coupled plates, characterize the other endmember (the "Marianas" type). Jarrard (1986) took this concept further and the basic model is still cited as an important explanation of first-order subduction zone variability (Stern, 2002). Ota and Omura (1992) proposed that variation in uplift rates of~120 ka marine terraces on the Ryukyu Islands of Japan could be explained by this model.…”

Large‐scale rigid‐body rotation in the mantle wedge and its implications for seismic tomography

“…They concluded that cold plumes are driven by RayleighTaylor instabilities that develop at the top of subducting slab. Diapirs rise through the mantle wedge along trajectories determined by the balance between buoyancy forces and mantle flow [Stern, 2002;Manea et al, 2005]. It was determined that both positive and negative seismic velocity anomalies are associated with the plumes [Gerya et al, 2006].…”

Subduction of the oceanic Hikurangi Plateau and its impact on the Kermadec arc

“…It has been known for decades that volcanic arcs are the result of that subduction process, as the descending plate dehydrates, causing partial melting in the overlying mantle. Consequently, arc lavas carry geochemical signals from the subducting plate, which includes the sediment cover, altered oceanic crust and serpentinized mantle [10][11][12] . In addition, signals of subducting intraplate seamounts (or LIPs) with geochemical compositions different to the subarc mantle can be traced in arc lavas 13,14 .…”