Rapid mass wasting following nearshore submarine volcanism on Kilauea volcano, Hawaii

The rapid mass wasting of shallow submarine basalts was documented during SCUBA dives along the flanks of Kilauea volcano, Hawaii during the Kii lava entry of the current eruption (19°20.5′N, 154°59.8′W). Lava entered the ocean at this site from mid-February to late March 1990, with several pauses. Dives on 19–20 March 1990 confirmed the widespread formation of lava pillows at this site over a water depth range of 20–40 m, and visual observations suggested that the resulting volcanic deposits were generally stable, despite the steep (∼40°) incline of the seafloor. (The pre-eruptive nearshore seafloor slope was ∼14°.) However, dives on 2 April 1990 revealed that nearly all submarine volcanic features had been subject to mass wasting, as the offshore area had been transformed into a debris field composed of material ranging in size from fine sand to boulder fragments. This generally featureless seascape extended uniformly to beyond the visual range of divers (∼60 m water depth). High-resolution multibeam bathymetry and sidescan imaging indicate that steeply sloped coarse sediment extends down the flanks of Kilauea in this area to abyssal depths, implying a linkage between nearshore submarine volcanism and deep-water deposits.