Izu–Bonin Arc

Izu–Bonin Arc
Name	Izu–Bonin Arc
Location	Pacific Ocean
Country	Japan
Type	Island arc
Length km	1400

Izu–Bonin Arc The Izu–Bonin Arc is an oceanic island arc system southeast of Honshu in the North Pacific Ocean, extending from the Izu Islands through the Bonin Islands toward the Mariana Islands. It forms part of a long convergent margin where the Pacific Plate subducts beneath the Philippine Sea Plate, producing a chain of volcanic islands, back-arc basins, and complex tectonic structures that have been central to studies by institutions such as the University of Tokyo, Woods Hole Oceanographic Institution, and the Japan Agency for Marine-Earth Science and Technology.

Geology and Tectonic Setting

The arc sits at the junction of the Pacific Plate, the Philippine Sea Plate, and the microplates around Japan Trench and Sagami Trough, interacting with features like the Kyushu-Palau Ridge and the Izu–Mariana Trench system. Plate convergence rates inferred from Global Positioning System networks and studies by Geological Survey of Japan and USGS correlate with seismicity catalogues from the Japan Meteorological Agency and the Centroid Moment Tensor Project. The arc's evolution involves back-arc extension linked to the opening of the Shikoku Basin and strike-slip motion related to the Izu Collision documented by researchers at Tokyo Institute of Technology and Stanford University. Lithospheric structure imaged by seismic tomography from projects like Hi-net and DONET reveals slab rollback, mantle flow, and complex slab morphology beneath the arc.

Volcanism and Petrology

Volcanism along the arc ranges from basaltic to dacitic and rhyolitic compositions, with petrological work by teams at National Institute of Advanced Industrial Science and Technology and Massachusetts Institute of Technology highlighting arc magmatism driven by slab dehydration and mantle wedge metasomatism. Geochemical signatures include enriched large-ion lithophile elements and depleted high-field-strength element patterns similar to other arcs such as the Mariana Islands and Aleutian Islands, reported in journals like Nature and Geology. Notable volcanic edifices studied include Miyake-jima, Sakurajima (as regional comparator), Iwo Jima, and submarine volcanoes investigated by ROV expeditions from NOAA and Japan Agency for Marine-Earth Science and Technology. Petrologists from ETH Zurich and University of Cambridge have used isotopic systems (Sr-Nd-Pb-Hf) to trace mantle and slab contributions, while experimental petrology at Carnegie Institution for Science constrains melting conditions.

Seismology and Subduction Processes

Seismicity beneath the arc includes interplate megathrust earthquakes like those recorded by the 1905 Mikawa earthquake historical catalogues and recent events monitored by the Japan Meteorological Agency and USGS seismic networks. Studies using offshore seismic arrays from Ocean Bottom Seismometer deployments and analyses by Lamont–Doherty Earth Observatory have imaged the subducting slab, including hydration, seismic anisotropy, and low-velocity zones associated with serpentinization. Slow-slip events and tremor documented by Hi-net and international collaborations inform models of segmental locking and rupture propagation that reference methods from Southern California Seismic Network studies and paleoseismology undertaken by University of California, Berkeley researchers.

Geomorphology and Bathymetry

The arc's topography features emergent islands, submerged seamounts, calderas, and the steep inner trench slope flanking the Izu–Ogasawara Trench; bathymetric mapping by General Bathymetric Chart of the Oceans projects and surveys by RV Kairei and RRS James Cook reveal complex volcanic chains and rifted domains comparable to the Mariana Trench region. Submarine landslides, mass-wasting deposits, and turbidite records recovered by International Ocean Discovery Program coring inform hazard assessments akin to those developed after studies of the Storegga Slide and Mount St. Helens deposits. Morphostructural analysis by teams at AIST and University of Hawaii integrates multibeam sonar, sidescan, and seismic reflection datasets.

Biological and Hydrothermal Ecosystems

Hydrothermal vent fields and chemosynthetic communities on submarine volcanoes support fauna studied by biologists from National Museum of Nature and Science (Japan), Smithsonian Institution, and Biodiversity Center of Japan. Species assemblages include vent-endemic polychaetes, gastropods, and crustaceans analogous to those described from the East Pacific Rise and Galápagos Rift, with molecular ecology contributions from Scripps Institution of Oceanography and University of British Columbia revealing biogeographic links. Coral reef habitats on shallow islands host taxa catalogued by the World Conservation Monitoring Centre and conservation assessments by IUCN while fisheries around islands involve stakeholders such as the Fisheries Agency (Japan).

Human Activity and Research History

Exploration and scientific research have involved historic voyages by institutions like HMS Challenger comparators, extensive Japanese oceanographic campaigns by Japan Agency for Marine-Earth Science and Technology, international collaborations including NOAA and International Ocean Discovery Program, and academic contributions from University of Tokyo and Woods Hole Oceanographic Institution. Human impacts include fisheries, airspace and maritime jurisdictions administered by Tokyo Metropolitan Government and national agencies, and hazard mitigation efforts by the Japan Meteorological Agency and municipal governments following eruptions and earthquakes similar to responses developed after Great Kantō earthquake. Ongoing multidisciplinary programs combine geology, geophysics, geochemistry, biology, and hazard science coordinated by universities and research organizations worldwide.

Category:Island arcs Category:Pacific Ocean