Bedforms on the submarine flanks of insular volcanoes: New insights gained from high resolution seafloor surveys

Abstract

A comparative analysis of bedform fields along the submarine flanks of insular volcanoes, characterized by different morpho-structural settings, volcanic and meteo-marine regimes (Vanuatu, Kermadec, Bismark, Madeira and Aeolian archipelagos), is presented here to provide insights on the size distribution, morpho-dynamic and genesis of such bedforms. Two main types of bedforms are recognized according to their size, location and preconditioning/triggering processes. Small-scale bedforms have wavelengths of tens to hundreds of metres and wave heights of metres. Because of their small-size, they are typically not recognizable at water depths greater than 400 m from vessel-mounted bathymetric surveys. Few examples of small-scale bedforms are reported from upper volcanic flanks, where steep gradients commonly hinder their formation. Their

Geomorphometric descriptions of archipelagic aprons off the southern flanks of French Frigate Shoals and Necker Island edifices, Northwest Hawaiian Ridge

“…3 Throughout the descriptions and discussions above, bedforms are described and interpreted to be evidence of slow-moving sediment creep. However, many recent studies of archipelagic aprons have described bedforms as the result of energetic turbidity currents (e.g., Wynn and Stow, 2002;Pope et al, 2018;Quartau et al, 2018;Santos et al, 2019;Casalbore et al, 2020). Individual French Frigate Shoals edifice and Necker Island edifice bedform crest heights, crest wavelengths, and water depths were measured, and plots are shown in Figures 15 and 20.…”

“…Individual French Frigate Shoals edifice and Necker Island edifice bedform crest heights, crest wavelengths, and water depths were measured, and plots are shown in Figures 15 and 20. Wynn and Stow (2002), Pope et al (2018), Santos et al (2019), and Casalbore et al (2020), and references therein discuss criteria to distinguish between bedforms caused by turbidity currents and sediment creep. Table 1 contrasts the differences in morphology and setting discussed in these studies to distinguish bedforms formed by energetic turbidity currents from those formed by slow, gravity-induced sediment deformation that is generally described as creep.…”

“…8,14,and 18). Creep can be generated by gradual gravitational sliding and slumping of unconsolidated sediment down a slope of lower gradients than would normally generate slides and slumps (e.g., Lee and Chough, 2001;Wynn and Stow, 2002), although many bedforms on archipelagic aprons are attributed to energetic turbidity currents (e.g., Wynn and Stow, 2002;Pope et al, 2018;Pope et al, 2018;Quartau et al, 2018;Casalbore et al, 2020). Creep is found on slopes of less than 1° all along the archipelagic aprons of the French Frigate Shoals and Necker Island edifices.…”

“…Studies in the 1980s of landslides at seamounts, guyots, and islands used either longrange sidescan sonar (e.g., Moore et al, 1989;Masson et al, 1992) or utilized early versions of multibeam echosounders (MBES) but created only sidescan backscatter images (i.e., Moore et al, 1989;Holcomb and Searle, 1991), bathymetric contour maps (e.g., Hollister et al, 1978;Vogt and Smoot, 1984;Smoot, 1985), or mesh grids (e.g., Taylor et al, 1975Taylor et al, , 1980Smoot, 1982Smoot, , 1983aSmoot, , 1983bSmoot, , 1985. Recently, studies have utilized modern multibeam data (e.g., Deplus et al, 2001;Masson et al, 2002;Mitchell et al, 2002;Bohannon and Gardner, 2004;Silver et al, 2009;Casalbore et al, 2010;Montanaro and Beget, 2011;Watt et al, 2012bWatt et al, , 2014Saint-Ange et al, 2013;Ramalho et al, 2015;Watson et al, 2017;Clare et al, 2018;Counts et al, 2018;Pope et al, 2018;Quartau et al, 2018;Santos et al, 2019;Casalbore et al, 2020) to provide complete, high-resolution digital terrain models of the geomorphology of various archipelagic aprons and submarine landslides. Although archipelagic aprons have never been described from this volcanically dormant area of the Northwest Hawaiian Ridge (Fig.…”

The role of sediment gravity flows on the morphological development of a large submarine canyon (Taiwan Canyon), north‐east South China Sea

“…The sediment waves in the lower reach of Taiwan Canyon are not the focus in this work because they have been proposed to be generated by unconfined turbidity currents flowing out of the West Penghu Canyon (Gong et al, 2012;Kuang et al, 2014). The formation of deep-water sediment waves has been attributed to multiple causes, including downslope turbidity currents (Wynn & Stow, 2002;Covault et al, 2014), along-slope contour (bottom) currents (Masson et al, 2002;Betzler et al, 2014), interactions between turbidity and contour currents (Normandeau et al, 2018) and submarine landslides (Hampton et al, 1996;Pope et al, 2018;Casalbore et al, 2020). In the following sections, the formation mechanisms of sediment waves in Fields 1 and 2 are analyzed in detail.…”