Volcanism in Response to Plate Flexure

• Published in: Science (American Association for the Advancement of Science) Vol. 313; no. 5792; pp. 1426 - 1428
• Main Authors: Hirano, Naoto, Takahashi, Eiichi, Yamamoto, Junji, Abe, Natsue, Ingle, Stephanie P, Kaneoka, Ichiro, Hirata, Takafumi, Kimura, Jun, Ishii, Teruaki, Ogawa, Yujiro, Machida, Shiki, Suyehiro, Kiyoshi
• Format: Journal Article
• Language: English
• Published: Washington, DC American Association for the Advancement of Science 08.09.2006; The American Association for the Advancement of Science
• Subjects: Asthenosphere; Crystalline rocks; Earth; Earth sciences; Earth, ocean, space; Exact sciences and technology; Geophysics; Igneous and metamorphic rocks petrology, volcanic processes, magmas; Lava; Lithospheres; Magma; Oceans; Plate tectonics; Tectonics; Tectonics. Structural geology. Plate tectonics; Volcanism; Volcanoes; Northwest Pacific; bathymetric maps; lava fields; Mesozoic; flexure; dredging; volcanism; Pacific Plate; trace-element analyses; mantle origin; plate boundaries; asthenosphere; sonar methods; fractures; plate movement; models; side-scanning methods; alkalic composition; Cretaceous; partial melting; chemical analysis; lithospheric faults; subduction; scientific cruises; extension tectonics; Lower Cretaceous; tectonic setting; Pacific Ocean; Phanerozoic; age
• ISSN: 0036-8075; 1095-9203
• DOI: 10.1126/science.1128235

Volcanism on Earth is known to occur in three tectonic settings: divergent plate boundaries (such as mid-ocean ridges), convergent plate boundaries (such as island arcs), and hot spots. We report volcanism on the 135 million-year-old Pacific Plate not belonging to any of these categories. Small alkalic volcanoes form from small percent melts and originate in the asthenosphere, as implied by their trace element geochemistry and noble gas isotopic compositions. We propose that these small volcanoes erupt along lithospheric fractures in response to plate flexure during subduction. Minor extents of asthenospheric melting and the volcanoes' tectonic alignment and age progression in the direction opposite to that of plate motion provide evidence for the presence of a small percent melt in the asthenosphere.