OS41B-08
Axial Seamount 2015 Eruption: A 127 m Thick, Microbially-Covered Lava Flow

Thursday, 17 December 2015: 09:45
3009 (Moscone West)
Deborah S Kelley1, John R Delaney1, William Chadwick2, Brendan Thomas Philip3, Susan G Merle4 and Cabled Array Ocean Observatories Initiative Team, (1)University of Washington Seattle Campus, Seattle, WA, United States, (2)Oregon State University/NOAA/PMEL, Newport, OR, United States, (3)University of Washington, Seattle, WA, United States, (4)Oregon State University, Newport, OR, United States
Abstract:
On April 24th, Axial Seamount on the Juan de Fuca Ridge erupted. This site now hosts the most advanced submarine volcanic observatory with a diverse, multidisciplinary array of 48 cabled instruments at its summit and base, and an instrumented state-of-the-art shallow profiling mooring providing real-time data to shore as part of NSF’s Ocean Observatory Initiative (Delaney et al., AGU-2015). The onset of the eruption was marked by more than 8000 earthquakes (Wilcock et al., AGU-2015; Garcia et al., AGU-2015) and a drop in the seafloor of 2.4 m (Nooner et al., AGU-2015). Follow-on analyses of hydrophone data (Tolstoy et al., AGU-2015) pointed to the location of the eruption as the Northern Rift zone.

During the OOI-NSF-UW Cabled Array maintenance cruise, the Northern Rift and eastern side of the caldera was mapped using the R/V Thompson’s EM302 system at. Differencing of 2007 (Hydrosweep) and 2013 EM302 bathymetric data indicated that the flow was ~ 7 km in length and up to 127 m thick, where it filled in a preexisting small depression. On July 26th, the ROV ROPOS dove near the toe of the northeastern lobe of the flow, the location of the highest bathymetric difference. The steep north face of this lobe is composed of glassy pillow flows: ROPOS ascended ~ 85 m before reaching the summit. Immediately upon reaching the summit, the vehicle was engulfed in a blizzard of biologically-produced ‘snowblower’ material issuing from distributed small sites of diffuse flow that reached 18°C. These areas hosted white filamentous bacteria, presumably methane metabolizers. Extensive areas of the flow summit were covered with orange microbial mats that completely masked the underlying pillows flows. Particle-poor diffuse fluids issued from microbially-covered collapse features along the summit, assumed to mark the main feeder channels. This eruption was markedly different than the Axial April 2011 eruption, which was characterized by vast sheet flows and extensive collapse zones.

<< Previous Abstract | Next Abstract