Large-scale catastrophic flank collapses in a steep volcanic ridge: The Pico–Faial Ridge, Azores Triple Junction

Catastrophic flank collapses and slumping in Pico Island during the last 130 kyr (Pico-Faial ridge, Azores Triple Junction)

“…Earlier studies in Pico have highlighted the existence of several large structures affecting the various volcanic complexes ( (1) On Pico's northern flank, a detailed analysis of high-resolution bathymetry and sub-aerial DEM, coupled with fieldwork and recent K-Ar dating on separated groundmass led Costa et al (2014) to report a 4 to 10 km 3 submarine debris deposit, interpreted as resulting from a northwards catastrophic collapse on the N flank of the old Topo Volcano, prior to ca. 70 ka.…”

“…(3) The WNW-ESE scarp on the southern flank of the Pico Stratovolcano ( Fig. 2B) has been interpreted either as an avalanche scar (Woodhall, 1974;Madeira and Brum da Silveira, 2003) or as a fault Féraud et al (1980), Demande et al (1982) and Costa et al (2014), respectively. Also shown a radiocarbon age (plus sign) from Nunes (1999).…”

“…850 ka ago on the eastern part of Faial Island ( Fig. 1, Hildenbrand et al, 2012a), which has evolved through short periods of voluminous volcanic construction intercalated with longer periods of major destruction by both tectonics and relatively largescale mass-wasting (Hildenbrand et al, 2012a(Hildenbrand et al, , 2012b.The evolution of these steep volcanic ridges appears intimately related to tectonic deformation, which may partly control the successive stages of volcanic growth and repeated episodes of destabilization, e.g., through largescale graben development (Hildenbrand et al, 2012a), flank collapses (Woodhall, 1974;Nunes, 1999;Mitchell, 2003;Mitchell et al, 2008;Costa et al, 2014), or large-scale slumping (Nunes, 1999;Hildenbrand et al, 2012bHildenbrand et al, , 2013Mitchell et al, 2012aMitchell et al, , 2013.…”

“…Despite the relatively small volume of the Azorean islands, increasing evidence for large-scale catastrophic destruction in the form of lateral flank collapses has been accumulated (Marques et al, 2013b;Costa et al, 2014;Sibrant et al, 2014Sibrant et al, , 2015aSibrant et al, , 2015b. Large-scale mass-wasting on Pico's N flank was interpreted by Costa et al (2014) as resulting from catastrophic collapse(s) towards the N. Pico's S flank is currently affected by an active large-scale slump with subsidence up to 1 cm/yr (Hildenbrand et al, 2012b), which comprises the western remnants of an earlier catastrophic collapse to the S. Though the current topography shows a well-defined scar extending much further to the E of the slump, which is suggestive of a flank collapse, there was until now no evidence of the catastrophic collapse, e.g.…”

“…Large-scale mass-wasting on Pico's N flank was interpreted by Costa et al (2014) as resulting from catastrophic collapse(s) towards the N. Pico's S flank is currently affected by an active large-scale slump with subsidence up to 1 cm/yr (Hildenbrand et al, 2012b), which comprises the western remnants of an earlier catastrophic collapse to the S. Though the current topography shows a well-defined scar extending much further to the E of the slump, which is suggestive of a flank collapse, there was until now no evidence of the catastrophic collapse, e.g. a debris deposit on the ocean bottom as recognized and described in the present work.…”