High-resolution mapping at Axial Seamount

August 8, 2016

45o 37.5′ N 124o 02.7′ W

We departed Newport, Oregon, at 7:00 a.m. in the fog and were welcomed back onto the northeast Pacific Ocean by surprisingly calm seas. We steamed west toward Axial Seamount at nine to 10 knots all day. The clouds remained overcast and it even sprinkled, and the seas gradually grew until, by evening, it felt like what we consider (oh so fondly) as being normal for the Juan de Fuca Ridge area.

Alexandra

Alexandra “Sasha” Belinsky strikes a pose in her immersion suit during our safety drill this morning.

The R/V Rachel Carson with MBARI’s pair of mapping AUVs is now at the Gorda Ridge. The mapping team is collecting high-resolution bathymetry at hydrothermal sites named Seacliff and NESCA (Northern Escanaba Trough). We had planned to dive on vents at both sites with the ROV on our transit north during the R/V Western Flyer’s first leg, but bad weather forced us to pass them by. Even though we can’t dive there this summer, the improved bathymetry will help us put into better context previous submersible dives, camera tows, Deep Sea Drilling Project drill holes, and other work, both by MBARI and other researchers.

While the R/V Rachel Carson was at Axial Seamount on this expedition, the mapping team expanded our coverage of the volcano’s summit and rift zones, and we are diving with the ROV on some of the areas identified in the new maps. The 11 mapping AUV surveys completed at Axial this summer include: the completion of  mapping of the 2015 flows that the AUV Sentry began mapping last summer; additional coverage of both north and south rift zones; the mapping of some large lava flows that poured from Axial’s deep south rift into the axial valley of the Vance Segment of the Juan de Fuca Ridge (which runs between the zero and five kilometer marks of the scale bar in the figure and continues south off the map); and a track that zig-zags over the summit designed to compare to past and future surveys to detect vertical deformation of the summit of the volcano from year to year. See our August 1 cruise log for more information about the 2015 flows and the August 2 cruise log for more information about the enormous south rift flows.

AxialAUV2016_coverage_wFlows_sm

The coverage of the mapping AUVs at Axial Seamount as part of this expedition is shown in color, over previous years’ AUV coverage in grayscale, over ship-based mapping in faded, pastel color. The AUV data grids are set at one-meter horizontal resolution. The data shows slopes, and their color ramps span the depth ranges of the individual 18-hour AUV surveys. The previous AUV data include coverage that was remapped after both of the 2011 and 2015 eruptions, the flows from which are outlined in brown and red, respectively. The color ramp for the ship-based data is 1,250 to 2,850-meters depth; white areas are where there is no ship-based mapping coverage since GPS navigation became standard.

—Jenny Paduan