Izu–Ogasawara–Mariana Arc

Izu–Ogasawara–Mariana Arc
Name	Izu–Ogasawara–Mariana Arc
Location	Northwest Pacific Ocean

Izu–Ogasawara–Mariana Arc is a long volcanic island arc system in the northwest Pacific bounded by the Philippine Sea Plate, the Pacific Plate, and the Eurasian Plate and forming a chain that includes the Izu Islands, the Ogasawara (Bonin) Islands, and the Mariana Islands. The arc connects geologic features that span from the Izu Peninsula region near Mount Fuji through the Izu Islands and Ogasawara Islands to the Mariana Islands and Guam, and it is associated with major convergent plate interactions, active volcanism, deep trenches, and unique biogeographic zones such as the Mariana Trench and the Ogasawara National Park.

Geography and extent

The arc system extends south-southeast from the vicinity of Honshu and the Izu Peninsula past the Izu Islands and Oshima Island through the Bonin Islands including Chichi-jima and Hahajima, then continues to the Mariana Islands chain encompassing Saipan, Tinian, and Guam before terminating near the Marianas Trench, adjacent to Wake Island and far-field features such as Micronesia and Palau. This zone intersects maritime boundaries proximate to Japan, United States territories, and exclusive economic zones of Philippines and Taiwan, and it lies near major oceanographic currents including the Kuroshio Current and features studied by institutions like the Japan Agency for Marine-Earth Science and Technology and the University of Tokyo.

Tectonic setting and plate interactions

The arc is driven by subduction of the Pacific Plate beneath the Philippine Sea Plate and complex interactions with the Eurasian Plate and microplates such as the Izu–Bonin–Mariana microplate and the Okinawa Plate; related transform and back-arc processes involve the Philippine Fault Zone and the Izu Collision Zone. Key tectonic events include slab rollback, trench migration, and back-arc spreading linked to features like the Bonin Trench and the Mariana Trench. Research by organizations including the Geological Survey of Japan and the United States Geological Survey integrates seismic tomography from networks such as the Hi-net and projects like TOPO-Asia to image the subducting slab and mantle flow beneath arc volcanoes such as Mount Mihara and submarine edifices explored by ROV Alvin and Shinkai 6500.

Volcanism and island formation

Arc volcanism produces a spectrum of magmatism from calc-alkaline arc volcanoes like Mount Fuji-adjacent systems to high-magnesium basalts and boninites exemplified in the Ogasawara and Bonin Islands; processes include flux melting above the slab and mantle wedge metasomatism with contributions traced by isotopic studies referencing laboratories at Massachusetts Institute of Technology, University of California, Santa Cruz, and Woods Hole Oceanographic Institution. Island formation involves seamount accretion, submarine eruptions documented by NOAA cruises, and emergent stratovolcano construction seen on Iwo Jima, Anatahan, and Asuncion Island, while themes of rifting and crustal thinning link to studies by Scripps Institution of Oceanography and the National Oceanic and Atmospheric Administration.

Seismicity and tsunami hazard

The arc is seismically active with frequent intermediate-depth and shallow earthquakes related to slab interface events, intraslab rupture, and volcanic earthquakes recorded by networks like JMA and IRIS; notable seismic events have been studied in relation to the 1707 Hōei earthquake region, the 1923 Great Kantō earthquake tectonic context, and farther south with analogues to the 1990s Mariana seismicity. Tsunami hazard assessments by bodies such as the Intergovernmental Oceanographic Commission and Pacific Tsunami Warning Center emphasize propagation across the Philippine Sea to Japan, Guam, Taiwan, and Philippines, and emergency planning involves agencies including the Japan Meteorological Agency and the Federal Emergency Management Agency.

Geological history and evolution

Stratigraphic and geochronologic investigations using radiometric methods carried out by institutions such as Geological Survey of Japan, University of Tokyo, and Massachusetts Institute of Technology document arc initiation in the Cretaceous through Cenozoic episodes, progressive southward migration, and episodes of back-arc extension that shaped features like the Shikoku Basin and the Back-arc basins studied by expeditions aboard RV Kairei and R/V Kaimei. Tectonostratigraphic reconstructions reference the breakup of the Izanagi Plate and interactions with the Pacific Plate, and paleomagnetic studies link volcanic sequences on islands like Chichijima and Hahajima to plate rotations and mantle dynamics constrained by projects at ETH Zurich and Lamont-Doherty Earth Observatory.

Biodiversity and ecosystems

Island biogeography along the chain supports endemic terrestrial and marine taxa recorded by surveys from Ogasawara National Park, Center for Biodiversity and Conservation, and museums such as the Natural History Museum, London and the Smithsonian Institution. Unique faunal assemblages include endemic birds noted by ornithologists at BirdLife International, reef systems with corals studied by Coral Reef Alliance and The Ocean Conservancy, and hydrothermal and deep-sea communities investigated by NOAA Fisheries and Japan Agency for Marine-Earth Science and Technology using submersibles like ROV Jason. Conservation programs involve UNESCO designations, national parks, and research collaborations with universities including University of Hawaii and James Cook University.

Human activity and research infrastructure

Human presence includes settlements on Chichijima, Hahajima, Saipan, and Guam with historical links to explorers such as Commodore Matthew Perry and events including World War II campaigns involving Battle of Saipan; infrastructure supports fisheries, tourism, and military facilities under administrations including Japan Self-Defense Forces and the United States Department of Defense. Scientific infrastructure comprises observatories like Sakurajima Volcano Observatory collaborations, marine research vessels including RV Kairei and JOIDES Resolution, and international programs such as IODP and GEBCO that map and sample arc structure and sediments, while conservation initiatives engage organizations such as UNESCO World Heritage Centre and local governments.

Category:Volcanic arcs