Extent and Volume of Lava Flows Erupted at 9°50′N, East Pacific Rise in 2005–2006 From Autonomous Underwater Vehicle Surveys

• Published in: Geochemistry, geophysics, geosystems : G3 geophysics, geosystems : G3, 2022-03, Vol.23 (3), p.n/a
• Main Authors: Wu, Jyun‐Nai, Parnell‐Turner, Ross, Fornari, Daniel J., Kurras, Gregory, Berrios‐Rivera, Natalia, Barreyre, Thibaut, McDermott, Jill M.
• Format: Article
• Language: English
• Subjects: autonomous underwater vehicle; Autonomous underwater vehicles; Bathymetric data; Cycles; Dikes; Embankments; eruption cycles; Lava; Lava flows; Magma; mid‐ocean ridges; Ocean floor; Oceans; Polls & surveys; Resolution; Ridges; seafloor mapping; Sonar; Sonar data; Sonar imagery; submarine volcanism; Surveying; Surveys; Underwater vehicles; Volcanic eruption effects; Volcanic eruptions; Volcanism; Volcanoes
• ISSN: 1525-2027; 1525-2027
• DOI: 10.1029/2021GC010213

Seafloor volcanic eruptions are difficult to directly observe due to lengthy eruption cycles and the remote location of mid‐ocean ridges. Volcanic eruptions in 2005–2006 at 9°50′N on the East Pacific Rise have been well documented, but the lava volume and flow extent remain uncertain because of the limited near‐bottom bathymetric data. We present near‐bottom data collected during 19 autonomous underwater vehicle (AUV) Sentry dives at 9°50′N in 2018, 2019, and 2021. The resulting 1 m‐resolution bathymetric grid and 20 cm‐resolution sidescan sonar images cover 115 km2, and span the entire area of the 2005–2006 eruptions, including an 8 km2 pre‐eruption survey collected with AUV ABE in 2001. Pre‐ and post‐eruption surveys, combined with sidescan sonar images and seismo‐acoustic impulsive events recorded during the eruptions, are used to quantify the lava flow extent and to estimate changes in seafloor depth caused by lava emplacement. During the 2005–2006 eruptions, lava flowed up to ∼3 km away from the axial summit trough, covering an area of ∼20.8 km2; ∼50% larger than previously thought. Where pre‐ and post‐eruption surveys overlap, individual flow lobes can be resolved, confirming that lava thickness varies from ∼1 to 10 m, and increases with distance from eruptive fissures. The resulting lava volume estimate indicates that ∼57% of the melt extracted from the axial melt lens probably remained in the subsurface as dikes. These observations provide insights into recharge cycles in the subsurface magma system, and are a baseline for studying future eruptions at the 9°50′N area. Plain Language Summary Volcanism on Earth primarily occurs in the oceans, at ridges where plates spread apart and molten rock intrudes the crust and erupts onto the seafloor. These eruptions frequently repave the seafloor and massively impact deep‐sea ecosystems, but they remain poorly understood because the difficulties of collecting data in the deep ocean. We present meter‐scale mapping of the volcanic system at the East Pacific Rise, 9°50′N, which erupted in 1991–1992 and 2005–2006, and is one of the best‐studied hydrothermal vent areas. Using sonar data collected using underwater robots before and after the 2005–2006 eruptions, we identify the margins of lava flows that paved over the seafloor, and estimate their thickness and volume. Lava flowed as far as 3 km from the mid‐ocean ridge, covering an area similar in size to Manhattan Island, NY. Using depth differencing between pre‐