“Grand” petit-spot volcanism off the Japan Trench
Abstract
Petit-spot volcanoes are a recently discovered type of small intraplate volcanoes that erupt on the outer rise of subducting plates. At petit-spot regions on the outer rise of the Japan Trench, an anomalously shallow acoustic basement reflector is widely distributed, leading to the hypothesis that it corresponds to sills or sheet-like lava flows and is associated with petit-spot magmatism. Here we report discoveries from the first drilling into the shallow acoustic basement off the Japan Trench. The basement is composed of petit-spot basalt, which is less altered with fewer vesicles than those exposed on the seafloor, resulting in higher bulk density and P-wave velocity. The lack of baked margins at the sediment-basalt boundary suggests that the basalt erupted as a lava onto the seafloor and was covered subsequently by 60 metres of sediment deposited over the past 3.6 Ma. Similar basalt ages and compositions at the drill site and an adjacent petit-spot knoll exposed on the seafloor, together with regional distribution of acoustic basement, suggest that the petit-spot volcanic base extends horizontally for at least 18 kilometres and potentially for hundreds of kilometres. Consequently, petit-spot volcanoes may have a greater impact on geochemical cycling and seismogenesis than previously thought.
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BibTeX
@misc{yamaguchi2026grand,
title = {{“Grand” petit-spot volcanism off the Japan Trench}},
author = {Asuka Yamaguchi and Hiroko Kitajima and Norikatsu Akizawa and Olivier Fabbri and Matt J. Ikari and Kenji M. Matsuzaki and Takashi Miyazaki and Yasuyuki Nakamura and Andrew P. Roberts and Paola Vannucchi and Hirano Naoto and Gou Fujie and Hanaya Okuda and Ayumu Miyakawa and Natsumi Okutsu and Yuya Akamatsu and Lottie Atton and Takanori Kagoshima and Taro Kido and Rachel Lauer and Jennifer M. Lington and Kazuto Mikuni and Francesco Narduzzi and Katie Preece and Louisa H. Stokes and Fuka Takuwa and Taizo Uchida and Hayato Ueda and Christopher Yen and Erwan Le Ber and Adam Wspanialy and Edoardo Barbero and Chin-Yeh Chen and Jose-Abel Flores and Mila Huebsch and Yuji Kato and Eun Young Lee and Jason P. Morgan and Sebastien Pilet},
howpublished = {EarthArXiv},
year = {2026},
month = oct,
doi = {10.31223/x54v4s},
url = {https://eartharxiv.org/repository/view/15417/},
note = {CC BY-NC-SA 4.0},
}
RIS
TY - UNPB
TI - “Grand” petit-spot volcanism off the Japan Trench
AU - Asuka Yamaguchi
AU - Hiroko Kitajima
AU - Norikatsu Akizawa
AU - Olivier Fabbri
AU - Matt J. Ikari
AU - Kenji M. Matsuzaki
AU - Takashi Miyazaki
AU - Yasuyuki Nakamura
AU - Andrew P. Roberts
AU - Paola Vannucchi
AU - Hirano Naoto
AU - Gou Fujie
AU - Hanaya Okuda
AU - Ayumu Miyakawa
AU - Natsumi Okutsu
AU - Yuya Akamatsu
AU - Lottie Atton
AU - Takanori Kagoshima
AU - Taro Kido
AU - Rachel Lauer
AU - Jennifer M. Lington
AU - Kazuto Mikuni
AU - Francesco Narduzzi
AU - Katie Preece
AU - Louisa H. Stokes
AU - Fuka Takuwa
AU - Taizo Uchida
AU - Hayato Ueda
AU - Christopher Yen
AU - Erwan Le Ber
AU - Adam Wspanialy
AU - Edoardo Barbero
AU - Chin-Yeh Chen
AU - Jose-Abel Flores
AU - Mila Huebsch
AU - Yuji Kato
AU - Eun Young Lee
AU - Jason P. Morgan
AU - Sebastien Pilet
PY - 2026
DA - 2026/10/09
PB - EarthArXiv
DO - 10.31223/x54v4s
UR - https://eartharxiv.org/repository/view/15417/
AB - Petit-spot volcanoes are a recently discovered type of small intraplate volcanoes that erupt on the outer rise of subducting plates. At petit-spot regions on the outer rise of the Japan Trench, an anomalously shallow acoustic basement reflector is widely distributed, leading to the hypothesis that it corresponds to sills or sheet-like lava flows and is associated with petit-spot magmatism. Here we report discoveries from the first drilling into the shallow acoustic basement off the Japan Trench. The basement is composed of petit-spot basalt, which is less altered with fewer vesicles than those exposed on the seafloor, resulting in higher bulk density and P-wave velocity. The lack of baked margins at the sediment-basalt boundary suggests that the basalt erupted as a lava onto the seafloor and was covered subsequently by 60 metres of sediment deposited over the past 3.6 Ma. Similar basalt ages and compositions at the drill site and an adjacent petit-spot knoll exposed on the seafloor, together with regional distribution of acoustic basement, suggest that the petit-spot volcanic base extends horizontally for at least 18 kilometres and potentially for hundreds of kilometres. Consequently, petit-spot volcanoes may have a greater impact on geochemical cycling and seismogenesis than previously thought.
ER -