E Spain ^1,2 Rebecca Carey ^2* Joanne M Whittaker ² Vanessa Lucieer ² Jodi Fox ² S J Watson ¹ Caratori Tontini ³

• ¹ National Institute of Water and Atmospheric Research (NIWA), Auckland, Auckland, New Zealand
• ² University of Tasmania, Hobart, Australia
• ³ Università degli Studi di Genova, Genova, Italy

Monitoring of active seafloor processes requires repeat, comparable surveys to enable change detection. Change detection of the deep ocean floor however is rare due to a paucity of repeat data at appropriate resolution. Here, we use an exceptional suite of bathymetric surveys across a spatio-temporal range at the submarine Havre volcano, Kermadec Arc, Southwest Pacific to investigate geomorphic change over 13 years (2002, 2012, and 2015).The integration of bathymetric with ROV observations and sampling data refined geomorphic boundaries, and four geomorphic groups at varying scales are interpreted: (i) large-scale tectonic and volcanic features, e.g. faults, calderas; (ii) coherent volcanic products, e.g. lavas, (iii) clastic primary volcanic products, e.g. giant pumice deposits; and (iv) mass-wasting features and products, e.g. landslide scarps. Three 25 m resolution geomorphic maps for broad-scale feature change and high-resolution 1 m AUV bathymetry are used to develop a fine-scale geomorphic map that reveals additional landforms and processes. We integrate bathymetric data with sampling data and ROV video footage of the seafloor to refine geomorphic boundaries. We also integrate the results of previous geological studies of Havre to inform the geomorphic interpretation. Our map reveals a variety of geomorphic forms from a range of volcanic and mass wasting processes that aid in the interpretation of the growth and evolution of submarine volcanoes. One new observation is a significantly increased scale of cryptodome emplacement than recognized previously. This emplacement took place along two linear southern caldera ring faults and likely continued after the formation of the giant pumice raft on July 18, 2012. A key result is the extension of the timeline for emplacement of volcanic products associated with the 2012 eruption, revealing an additional 0.001 km3 volume growth on the primary dome (dome OP) between 2012 and 2015. This additional emplacement is documented here for the first time and extends the known volcanic emplacement timeline from three months to a maximum of three years. Our work reveals seafloor modification continuing long after an observed volcanic eruption event, as lingering lava emplacement and mass-wasting remobilizes newly erupted and older products that comprise the edifice.