Cone morphologies associated with shallow marine eruptions: East Pico Island, Azores

Neil C. Mitchell, Rachelle Stretch, Clive Oppenheimer, Daniel Kay, Christoph Beier

Research output: Contribution to journalArticlepeer-review

23 Citations (Scopus)

Abstract

Eruptions in shallow water typically produce cones of volcaniclastic material. In order to identify any systematic effects of water depth and other environmental parameters on cone morphology, we have measured the heights and widths of cones in multibeam echo-sounder data from a submarine ridge extending southeast from Pico Island, Azores. XRF analyses of dredged samples show that lavas here vary compositionally from alkali basalt to trachybasalt and trachyandesite. Cones in deeper water are generally steep-sided with upper flanks close to 30°, the dip of talus at the angle of repose. However, height/width ratios of cones vary more in shallow water (200-400-m summit depth) with extreme values below 0. 1; while some shallow-water cones are steep-sided as in deep water, others are much flatter. Three such cones lie on a bench at 300-m depth immediately east of Pico Island and have flank slopes of only 10-20°. We speculate that exceptionally shallow cone slopes here were produced by forced spreading of the erupting columns on reaching the water-air density barrier.

Original languageEnglish
Pages (from-to)2289-2301
Number of pages13
JournalBulletin of Volcanology
Volume74
Issue number10
DOIs
Publication statusPublished - 2012
Externally publishedYes

Keywords

  • Cone morphologies
  • Pico Island
  • Shallow marine eruptions
  • Volcaniclastic material

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