Syn-eruptive edifice collapses during the Cumbre Vieja (Canary Islands) 2021 eruption

<p>During September-December 2021, the Cumbre Vieja eruption (La Palma, Canary Islands) was characterised by simultaneous explosive and effusive activity (Longpr&#233;, 2021; Pankhurst et al., 2021).&#160; The eruption produced a ~200 m high complex pyroclastic cone (Romero et al., 2022). A series of syn-eruptive lateral collapses modified the edifice morphology and caused sporadic breaching towards the west-northwest, influencing the nature and distribution of eruptive hazards.</p><p>We documented these destructive events using tremor and seismic data, as well as direct visual and thermal observations of the eruptive activity. In addition, UASs were used for aerial surveys and DEM generation in late September 2021. Field descriptions of the resulting deposits and stratigraphic sampling of tephra fallout were carried out in October and November 2021. Microanalysis of pyroclastic fragments included scanning electron microscope and electron microprobe for textural and compositional characterisation.</p><p>Two classes of collapse events were observed: the first involved a substantial portion of the cone and led to its horseshoe scar morphology; the second mainly affected ramparts of pyroclasts that separated vents along the fissure. The largest breaching event, which occurred on September 25, was generated by a high eruption rate and associated rapid deposition of pyroclasts on a steep pre-eruptive surface. Smaller collapses resulted from rapid pyroclastic agglutination on the conduit/fissure.</p><p>Some collapses triggered an immediate and substantial increase in the lava flux presumably through release of lava that has been stored in the vent and/or shallow plumbing system. The largest collapses produced lava flows up to 10 m thick which rafted decameter-sized chunks of the failed edifice. In some cases, these outpourings inundated residential areas. Collapses were sometimes followed by an increase in the eruption intensity, forming lava fountains up to several hundred metres in height; we infer these fountains resulted from unloading of the shallow plumbing system.</p><p>The 2021 eruption of Cumbre Vieja volcano provides a rare opportunity to document recurrent, syn-eruptive collapses of the vent edifice during a cone-forming eruption, and to identify and characterise the hazards associated with this common type of activity.&#160;</p><p>References:</p><p>Longpr&#233;, M. A. (2021). Reactivation of Cumbre Vieja volcano. Science, 374(6572), 1197-1198. Doi: 10.1126/science.abm9423</p><p>Pankhurst, et al. (2022). Rapid response petrology for the opening eruptive phase of the 2021 Cumbre Vieja eruption, La Palma, Canary Islands. Volcanica, 5(1), pp. 1&#8211;10. Doi: 10.30909/vol.05.01.0110.</p><p>Romero et al. (2022). Volume and stratigraphy of the Cumbre Vieja 2021 eruption tephra fallout, La Palma Island. VMSG Virtual Annual Meeting, 10-12th January 2022, Manchester, United Kingdom.</p>