RCA Operations Full Steam Ahead

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A small collapse basin is marked by pillars, arches and isolated columns of basalt. These areas form as lava drains out from deep lava pools. Credit: UW/NSF-OOI/ROPOS-CSSF. V14.

It has been a very busy few days onboard the R/V Thompson. Since leaving port just only one week ago, the RCA and Jason team has completed Shallow Profiler Mooring work at the Oregon Offshore, Slope Base and Axial Base sites, and turned seafloor instruments at two of the three sites. They have pounded out a series of 17 dives already in the program, including ones to 2600 m (8530 ft) and 2900 m (9514 ft) waters depth and an ~ 22 hr steam to Axial Base – way to go team.

From Axial Base, the R/V Thompson transited ~ 2 hrs to begin work in the ASHES and International District hydrothermal fields at the summit of Axial Seamount. Working in Axial Caldera is one of the teams, favorites because of the spectacular, ever changing scenery we can see through the eyes of the robotic vehicle working nearly a mile beneath the oceans surface. Here, fed by volcanic gases emanating from magma chambers ~ 2 km beneath the seafloor life thrives in nearly freezing seawater and in perpetual darkness.

During testing of the cabled high definition camera, which streams live imagery to shore every three hours, the camera lights up Jason at working at nearly a mile beneath the oceans surface on this active volcano. Credit: UW/OOI-NSF. V20.

Once reaching the seafloor, the terrane is reminiscent of terrestrial eruption site Craters of the Moon or of the Hawaiian shield volcanoes. However, at a mile down the only lights are those provided by Jason, yielding an often eerie seascape – frozen rivers of lava, skylights – open pits in lava flows that provide glimpses deep into the lava tubes that once fed surface flows, extended anastomosing fields of collapse pits that look like river channels, and huge pillow basalts marking the ends of eruptions. During the 2011 eruption, lava flows reached to within ~ 300 m of the ASHES hydrothermal field, and in 2015 ash rained down onto cabled instruments at the Central Caldera site.

The UW-APL-built high definition camera lights up the 12-13 ft tall hot spring deposit called Mushroom, nearly 5000 ft beneath the oceans surface at the summit of Axial Seamount. Credit: UW/NSF-OOI/WHOI,V18.

On August 6, Jason began working in the ASHES hydrothermal field – completing the important task of replacing the high definition camera focused on the Mushroom underwater hot spring. Once testing of the camera is completed, every three hours the camera will light up the face of Mushroom, imaging the beautiful animals that thrive on the outer face of the chimney awash in mixtures of hydrothermal fluid and seawater. This camera, built by the UW Applied Physics Laboratory, is one of the only in the worlds’ oceans that provides time-series imaging of the dynamic and evolving biological communities at an underwater hot spring, and allows documentation of the growth and collapse of small metal sulfide-rich spigots that sprout from the base and top of the main edifice. Work at ASHES also included Jason swapping out a CTD instrument that was installed through an NSF award to Dr. Bill Chadwick (Oregon State University) to examine the emission of subsurface brines associated with seafloor eruptions and an NSF-funded thermistor array, as part of a project lead by Dr. Karen Bemis (Rutgers University) to quantify venting and heat flux at this site.

Beautiful blue ciliates (single-celled organisms), tube worms – some coated in feathery white filamentous bacteria, and limpets thrive in the warm fluids issuing from the Tiny Village site. Credit: UW/NSF-OOI/WHOI, V19.

From ASHES, the Thompson transited east across the caldera to the International District Hydrothermal Field where work is focused on turning chemical sensors in two of the active hot springs (Diva and Escargot) and a digital still camera at the Tiny Village site – a beautiful diffuse flow site covered in orange and white bacterial mats, small tube worms with red plumes, and purple-blue ciliates, all underlain by bright orange brown patches of oxidized sulfide.  Jason is now transiting to the seafloor to complete this work.