Abstract
Understanding how large eruptions and landslides are recorded by seafloor morphology and deposits on volcanic island flanks is important for reconstruction of volcanic island history and geohazard assessment. Spectacular fields of bedforms have been recognised recently on submerged flanks of volcanic islands at multiple locations worldwide. These fields of bedforms can extend over 50 km, and individual bedforms can be 3 km in length and 150 m in height. The origin of these bedform fields, however, is poorly understood. Here, we show that bedforms result from eruption-fed supercritical density flows (turbidity currents) in some locations, but most likely rotational landslides at other locations. General criteria are provided for distinguishing between submarine bedforms formed by eruptions and landslides, and emphasise a need for high resolution seismic datasets to prevent ambiguity. Bedforms associated with rotational landslides have a narrower source, with a distinct headscarp, they are more laterally confined, and internal bedform structure does not suggest upslope migration of each bedform. Eruption-fed density currents produce wide fields of bedforms, which extend radially from the caldera. Internal layers imaged by detailed seismic data show that these bedforms migrated up-slope, indicating that the flows that produced them were Froude supercritical. Due to the low density contrast between interstitial fluid and sediment, the extent and dimensions of submarine eruption-fed bedforms is much greater than those produced by pyroclastic density currents on land.
Highlights
Silicic caldera-forming eruptions and landslides on volcanic islands represent some of the highest sediment flux events on Earth
It is important to understand how eruptions and landslides are recorded on submerged volcanic island flanks, and to distinguish between caldera-forming density current deposits and large submarine landslides as they pose distinctly different types of hazards
We show how these general criteria can help to understand the origin of submarine bedforms at other volcanic islands, and emphasise the need for detailed seismic surveys to reduce ambiguity
Summary
Silicic caldera-forming eruptions and landslides on volcanic islands represent some of the highest sediment flux events on Earth. They can transport tens to hundreds of cubic kilometres of material (Pyle, 1995; Hunt et al, 2013), most likely over a few hours to days. The landslides that occur on volcanic flanks can be unusually large, and involve both the subaerial and submarine domains of the edifice (White, 2000; Masson et al, 2006; Watt et al, 2012) They can evacuate material to surrounding basins through density flows (Le Friant et al, 2015; Watt et al, 2015). It is important to understand how eruptions and landslides are recorded on submerged volcanic island flanks, and to distinguish between caldera-forming density current deposits and large submarine landslides as they pose distinctly different types of hazards
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
