Fault-controlled submarine and subglacial explosive volcanism along the Terror Rift, Antarctica: New insights from integrated multichannel seismic data

Submarine volcanism in Antarctica remains one of the least explored yet geodynamically important processes on Earth. The Terror Rift, located in the western Ross Sea, is a zone of active extension, long-lived magmatism, and cryosphere–lithosphere interaction. Along its eastern boundary, the Lee Arch hosts several flat-topped seamounts that were previously interpreted as mud volcanoes based on vintage seismic data (Busetti et al., 2024). New evidence from Expedition NBP25-01 contradicts this interpretation (Tominaga et al., 2025). Rock samples from dredges and seafloor imagery confirm the presence of hyaloclastite breccia, hyalotuff, coherent lava fragments, ash, and agglutinated ash-lapilli, indicating a dominantly explosive volcanic origin for these edifices.

Here, we integrate new multichannel seismic profiles from Expedition NBP24-02 with reprocessed vintage multichannel data from Expedition IT-90RS, together with ground-truthing from Expedition NBP25-01, to assess the volcano–tectonic architecture of the Flapjack Field on the Lee Arch. The seismic profiles image extensive normal faulting along the eastern shoulder of the Terror Rift, with dense fault systems extending beneath the Flapjack Field. These fault corridors align with volcanic edifices and likely acted as preferential magma ascent pathways, enabling focused volcanism along the rift margin. Seismic images reveal a broadly consistent internal architecture across several flat-topped edifices, characterized by incoherent seismic facies in their central portions and spatially limited, outward-dipping stratified reflections forming progradational flank sequences. We interpret the incoherent central domains as massive hyaloclastite and breccia accumulated within confined eruptive cavities close to the vent, whereas the stratified flanks consist of volcaniclastic deposits emplaced by subaqueous density currents and gravity-driven mass flows. The general absence of pronounced seismic attenuation suggests that thick sequences of coherent volcanic rocks are absent, consistent with findings from Expedition NBP25-01 (Tominaga et al., 2025). The morphology and internal architecture support interpretation of these seamounts as subglacial volcanoes emplaced beneath grounded ice, analogous to tuyas or tindars. Our results demonstrate a tight coupling between fault-controlled magma ascent and subglacial volcanism along the eastern margin of the Terror Rift.

 

 

References:

Busetti, M., Geletti, R., Civile, D., Sauli, C., Brancatelli, G., Forlin, E., ... & Cova, A. (2024). Geophysical evidence of a large occurrence of mud volcanoes associated with gas plumbing system in the Ross Sea (Antarctica). Geoscience Frontiers, 15(1),  101727, https://doi.org/10.1016/j.gsf.2023.101727

Tominaga, M., Panter, K., Berthod, C., Tivey, M., Wu, J. N., Preine, J., ... & NBP25-01 Shipboard Science Support Staff. (2025). Subglacial explosive volcanism in the Ross Sea of Antarctica. Communications Earth & Environment, 6(1), 921, https://doi.org/10.1038/s43247-025-02878-x