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Crowd-sourcing observations of volcanic eruptions during the 2021 Fagradalsfjall and Cumbre Vieja events

The Cumbre Vieja eruption in La Palma, Spain, was as aesthetically spectacular as Fagradalsfjall. Volcanologist and science journalist Robin George Andrews referred to the eruption in the following terms:

“…a kaleidoscope of aesthetic wonders: Incandescent ink, with hues of crimson and burnt orange, pours into the cerulean sea; streaks of purple lightning dance around skyscraper-high lava fountains; curtains of molten rock spill out of a newborn lithic coliseum, creating the youngest land on Earth.”12

This eruption provides an interesting counterpoint to the Fagradalsfjall eruption described above. While the Fagradalsfjall eruption was of low-intensity and mostly confined to uninhabited valleys, the Cumbre Vieja eruption demonstrated more variable, but generally greater, intensity, deposited ash and lava through bustling towns and agricultural land, and was less easy to access safely3. Several factors contributed to a lower number of content creators visiting and documenting the event. Formal restrictions on eruption site access and drone flight permissions, motivated by fundamental safety concerns and urban disaster-zone control, meant that access was difficult or impossible for those not involved with the emergency response or immediate scientific campaigns. Furthermore, the cost of the eruption to people’s homes and livelihoods is painfully clear around the western side of La Palma, which raises ethical concerns associated with content production for aesthetic, artistic, or content-driven motivations.12, particularly if divorced from context. The displacement of the community, and the prevalence of second homes owned by expats, renders consent-seeking near impossible.

However, throughout this eruption and aftermath, close access has been possible for science groups working with the emergency response teams, for media organizations, and some content creators tied to media efforts. Just as for Fagradalsfjall, the resulting videography and photography has enabled novel observations of eruption phenomenology that will influence the models that emerge for this eruption (Fig. 3). The most striking example is the simultaneous activity of different eruptive styles in close proximity to one another (Fig. 3a–c). Specifically, after the eruption onset, eruptive activity localized into discrete vents formed an uppermost (eastern-most) vent characterized by relatively high intensity explosive activity that fed an unsteady buoyant plume, and a lowermost (western-most) vent characterized by lower intensity Hawaiian fountaining that fed lavas that flowed down-slope and into the ocean. These included lava fronts supplying incandescent blocks that fell >50 m from sea cliffs, and initiated failures of cliff ledges, secondary rock falls, and related plumes of dust. At times, a middle vent between the upper and lower vents exhibited mixed activity. This close spatial association of markedly different eruptive style requires explanation in terms of the geometry of the shallow plumbing system, and the spatial organization of gas–magma decoupling processes.13.14.

Fig. 3: Novel observations from the Cumbre Vieja eruption, La Palma, made possible via high-resolution crowd-sourced imagery.

a The close spatial association of different eruptive styles along-fissure localized in three vents. The upper vent (right of the vents visible in this image) manifests explosive activity and the eruption of ash and lapilli pyroclasts, while the lower vent (left of the vents visible in this image) manifests a lava fountain feeding clastogenic lavas. The middle vent between these left and right vents displays mixed eruptive style. Photograph taken on October 10th 2021, credit: Ulrich Kueppers. b The same close spatial association of very different eruptive activity taken on December 2na 2021, credit: Juanjo Ramos. c Plume behavior showing the ash- and lapilli-rich dark plume separate from the ash-poor and gas-dominated lower plume, credit: Edward Llewellin. d A broad overview of the advancing lava system and the source fountain (looking East). andF Repeat flights showing the evolution of the lava delta at the ocean entry point taken on and 30 September 2021 looking North-East, and F 11 November 2021 looking South-East. Credit: Alex Galdeano Rull. g Aerial view of the volcanic vent region taken from a helicopter piloted by the Spanish Civil Guard on 28 November 2021. hi The encroachment of lavas on settlements and plantations. Both h, i were taken on 3 January 2022 during a helicopter flight by the Spanish Civil Guard and gi are credit: INVOLCAN.

Media organizations (eg, Overon Aerial) shared drone data with volcanologists on the ground—an explicit example of the collaborative opportunities for which we argue here—allowing researchers to target their sampling and observations of lava flow-rates and fountain heights (Fig. 3d ), as well as the advance of the lava delta into the ocean (Fig. 3e, f). Dynamic hazard appraisal is safer by drone, and drone flights operated by media organizations have proven beneficial for scientists seeking access to fresh lava fronts, particularly when visible-light imaging is combined with thermal imaging. Similarly, the Civil Guard facilitated monitoring efforts by performing helicopter over-flights, footage from which could be used to assess proximal activity (Fig. 3g), damage to infrastructure and societal impacts in general (Fig. 3h, i), which can contribute to real-time hazard assessment. Direct observations from emergency services personnel were shared with science and monitoring teams actively and continuously (often via social-media and actively evolving WhatsApp groups), providing continuity when the science teams were not on-site.

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