East Epi

Geography & Climate

East Epi is located in Vanuatu, within the Vanuatu Volcanic Arc of the broader Southwestern Pacific Volcanic Regions. Situated at 16.68° S, 168.39° E in the Southern Hemisphere, the volcano lies within a tropical climate zone. With a summit elevation of 833 meters above sea level, East Epi is a moderately sized peak that remains accessible to hikers and researchers for much of the year. The volcanic landform is characterized as a cluster, which describes the physical shape and structure of the volcanic edifice as observed from the surface.

Geological Context

East Epi sits in a subduction zone, where one tectonic plate dives beneath another, creating intense heat and pressure that generates magma. Subduction zones are responsible for many of the world's most explosive volcanoes and deadliest eruptions. For communities in Vanuatu near East Epi, this tectonic setting means the volcano is capable of producing powerful explosive eruptions, pyroclastic flows, and lahars that can threaten populated areas within tens of kilometers of the summit. The dominant rock type is basalt / picro-basalt, a dark, fine-grained volcanic rock that forms from rapidly cooling, low-viscosity lava. Basaltic eruptions tend to be less explosive and produce fluid lava flows that can travel long distances. While less immediately dangerous than explosive eruptions, basaltic lava flows can destroy structures and infrastructure in their path, and volcanic gases released during these eruptions can affect air quality over a wide area.

Eruption History Summary

East Epi has 15 recorded eruptions in the geological database, spanning from 1920 CE to 2023 CE. The most powerful recorded event was a severe eruption capable of regional ash fall and pyroclastic flows in 1953 CE, reaching VEI 3 on the Volcanic Explosivity Index. This level of eruptive frequency indicates a persistently active volcanic system that warrants ongoing monitoring. With eruptive activity as recently as 2023 CE, East Epi remains an actively monitored volcano.

Significance

With a maximum recorded VEI of 3, East Epi has produced eruptions capable of generating pyroclastic flows and significant ash fall in the surrounding area. While not among the largest eruptions globally, VEI 3 events pose serious hazards to local populations and can disrupt regional air travel. With 15 recorded eruptions, East Epi has a substantial eruptive history that provides valuable data for understanding volcanic behavior and assessing future hazards in the Southwestern Pacific Volcanic Regions region. Given its recent activity, East Epi is closely monitored by geological survey organizations to provide early warning of future unrest.

GVP Reference Summary

The submarine East Epi group of basaltic and dacitic cones are located within a possible 10-km-diameter caldera off the NE coast of southern Epi Island in Vanuatu. Three cones (1-1.5 basal diameter), known as Epi A, Epi B (or Cioan), and Epi C, are located along the northern rim of the inferred caldera, though Beier et al. (2018) suggest an alternate to the post-caldera formation model. A few smaller cones are south of Epi B. Ephemeral islands were formed during eruptions at Epi B in 1920 and 1953. Explosive activity was reported in 1958 and 1960, discolored water was often seen during 1971-1974 and 1988, a new vent was detected in 1979, and explosive activity occurred in 1999, 2002, 2004, and 2023. The summit was at 34 m below sea level at the time of a 2001 survey, and a research cruise in 2013 (R/V Sonne SO-229; Haase et al, 2013) sampled six cones, including "very fresh pumice and lava bombs" from Epi B and "relatively old-looking" material from the others. The SO-229 cruise also recovered rhyodacitic pumice with mafic streaks, similar to that sampled by previous cruises, and described Epi B as "covered by massive blocks of pumice."

— Smithsonian Institution, Global Volcanism Program