Figure 26. a) Location of the COVIS sonar and RCA infrastructure in the ASHES Hydrothermal Field. Also shown are locations of the active ~ 4 m tall hydrothermal edifices ‘Mushroom’ and ‘Inferno’. c) The COVIS sonar in 2019 (Credit: Rutgers/UW/NSF-OOI/WHOI). The tower is 4.2 m tall and hosts a modified Reson 7125 SeaBat multibeam sonar mounted on a tri-axial rotator. The system was built by the UW Applied Physics Laboratory. d) Selected time-series images from COVIS showing bending of the plume eastward, e) a nearly vertical plume, and f) southward bending of the plume (after Fig. 7 Xu et al., 2020).

The Cabled Observatory Vent Imaging Sonar (COVIS) was installed on the OOI RCA in the ASHES hydrothermal field (Fig. 26 a-c) at the summit of Axial Seamount in 2018, resulting in the first long-term, quantitative monitoring of plume emissions (Xu et al., 2020). The sonar provides 3-dimensional backscatter images of buoyant plumes above the actively venting ‘Inferno’ and ‘Mushroom’ edifices, and two-dimensional maps of diffuse flow at temporal frequencies of 15 and 2 minutes, respectively. Sonar data coupled with in-situ thermal measurements document significant changes in plume variations (Fig. 26 d-f) and modeling results indicate a heat flux of 10 MW for the Inferno plume (Xu et al., 2020). COVIS will provide key data to the community investigating the impacts of eruptions on hydrothermal flow at this highly active volcano.

[1] Xu, G., Bemis, K., Jackson, D., and Ivakin, A., (2020) Acoustic and in-situ observations of deep seafloor hydrothermal discharge: OOI Cabled Array ASHES vent field case study. Earth and Space Science. Note: This project was funded by the National Science Foundation through an award to PI Dr. K. Bemis, Rutgers University – “Collaborative Research: Heat flow mapping and quantification at ASHES hydrothermal vent field using an observatory imaging sonar (#1736702). COVIS data are available through