Eruption triggering from connected magma storage at the Erta Ale ridge (East African Rift)

Abstract

Dyke intrusions and eruptions at nearby volcanoes can influence each other. However, the spatio-temporal connection of the magma storage and the dynamics of these events are rarely observed. We used InSAR, optical data, pixel offset tracking and seismicity to study two eruptions that occurred in the Erta Ale ridge within four months of each other causing caldera collapses. In November 2025, the Hayli Gubbi volcano erupted explosively sending an ash plume of ~14 km into the atmosphere. The eruption was preceded in July by a dyke intrusion and an eruption near the Erta Ale caldera. Dyking lasted 25 days and propagated southward for 36 km along the axis of the Erta Ale ridge, intruding a total of ∼0.4 km3 of mafic magma. The dyke also intercepted nearby magma reservoir, including a shallow (1.5 km depth) sill below Hayli Gubbi, causing minor uplift. Interestingly, Hayli Gubbi did not erupt until four months later, in November when InSAR shows that the contraction of a source under the Erta Ale caused the caldera collapse and simultaneous explosion and collapse at Hayli Gubbi. The July-November events suggests that the magmatic systems of Erta Ale and Hayli Gubbi are connected and that along axis dyke intrusion is a possible mechanism feeding other magma chambers ultimaltey triggering eruptions. We suggest that mafic magma was injected in Hayli Gubbi in July and again in November. Possible magma mixing with the residing melt occurred leading to the Haily Gubbi eruption. This is consistent with separate explosions and two plumes of likely different composition during the eruption (Ayalew et al., in preparation).CP and ALR are supported by the Space It Up project funded by the Italian Space Agency (ASI) and the Ministry of University and Research (MUR) under contract n. 2024-5-E.0 CUP n. I53D24000060005.