A New Class of Submarine Explosive Volcanic Events: Nautilian Eruptions.
Abstract
The characterization and understanding of subaqueous explosive eruption styles has lagged behind that of their subaerial counterparts due to a paucity of observations of both active eruptions and their products on the seafloor. New definition of at least two distinct modes of submarine explosive activity reflect progress in this area: Poseidic(occurring at depths of ~1000 m) and Neptunian(involving gas-rich, highly evolved pumice-forming eruptions). Recent high resolution multibeam mapping and remotely operated vehicle (ROV) explorations of shallow (<400 meters) explosive eruption sites in the marine environment have enhanced understanding of the formation of large, buoyant, mafic scoria that occasionally reach the sea surface. Historic accounts and recent observations document five such basaltic "balloon" eruptions, mostly associated with oceanic island hotspots. Here we propose to label this eruption style as 'Nautilian' after the marine cephalopod, Nautilus, which uses a mixture of internal gas and fluids to regulate its buoyancy in the water column. Nautilian eruptions occur over a limited range of water depths (200-400 m) and typically involve CO2-rich basaltic magma with alkaline affinity. Effusive and explosive activity may take place simultaneously with the production of both highly vesicular pillow lava and abundant tephra. A subset of the scoriaceous products have sufficient gas volumes to be highly buoyant, often with large internal bubbles. Studies of the volatile contents in melt inclusions from several of the eruptions suggest that volatile fluxing and accumulation of CO2-rich vapor are important factors in the production of the extensive vesicularity. The eruptions last from weeks to months and produce accumulations of volcaniclastic material and lavas that are somewhat analogous to the formation of subaerial scoria cones but with more irregular morphologies. Ephemeral, low-temperature hydrothermal systems with chemosynthetic bacteria commonly form near the vent sites and may persist for decades. Nautilian eruptions fall in a spectrum of subaqueous explosive activity involving basaltic magma occurring from depths of 1000 meters (Poseidic) to the near surface (Surtseyan).
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.V43H0191C
- Keywords:
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- 8408 Volcano/climate interactions;
- VOLCANOLOGY;
- 8414 Eruption mechanisms and flow emplacement;
- VOLCANOLOGY;
- 8424 Hydrothermal systems;
- VOLCANOLOGY;
- 8427 Subaqueous volcanism;
- VOLCANOLOGY