Development and hazard potential of dike-fed eccentric vents during the 2021 Cumbre Vieja eruption, La Palma (Canary Islands)

Abstract

During the first stage of the Tajogaite 2021 eruption at Cumbre Vieja volcanic ridge on La Palma Island, a scoria cone formed when four major vents merged into one main eruptive fissure. The explosive upper part of the volcanic complex generated columns of gas and ash that reached about 9 km a.s.l. while the effusive lower part produced lava flows covering some 12.4 km2. At later stages of the eruption, multiple fractures and more than 100 eccentric and distal vents opened at distances up to three kilometres from the main eruptive fissure. The new vents issued degassed pāhoehoe lavas that rapidly invaded previously unaffected urban and agricultural areas. The aligned vents, fissures and fractures strike NW-SE, N-S and ENE-WSW. Spatial and field analyses suggest that the eruption was supplied with magma through two feeder dikes whose location was largely controlled by pre-existing crustal discontinuities and heterogeneities. Feeder-dike induced surface deformation, such as a graben, tectonic fractures of various sizes, and local flank collapses of the scoria cone, occurred during the opening of the vents. Detailed studies of the relationship between tectonic fractures, gas emission, and dike propagation can be used to improve assessment of potential hazards during evolving eruptive dynamics and vent openings in monogenetic volcanoes.