January 31, 2023 Eruption of East Epi

Reference #13678:

The East Epi group, consisting of multiple submarine cones within a postulated caldera, lies off the eastern coast of Epi Island in Vanuatu (figure 6). Three cones (Epi A, B, and C) are located 4-10 km NNE from the Epi Island, with additional smaller cones south of Epi B (figure 7). Ephemeral islands were formed during eruptions 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 February 1999, March 2002, and February 2004. A March 2004 bathymetric survey revealed that Epi B was about 300 m tall with a diameter of about 1.8 km at the base; the summit crater was about 150 m in diameter, the crater floor was at a depth of 90 m, and the highest point was on the NW rim of the summit crater, at a depth of 34 m. This report covers a new eruption during January through February 2023 that was characterized by phreatic explosions, a growing cone, and ash emissions. Information primarily comes from the Vanuatu Meteorology and Geo-Hazards Department (VMGD).

According to the Wellington VAAC, a low-level ash and sulfur dioxide plume was identified in satellite data at 0730 on 31 January 2023. VMGD reported that residents saw gas-and-steam emissions at the ocean’s surface around 0748 (figure 8) and phreatic explosions that ejected gas and tephra 100 m above the water (figure 9). Observers also reported that they saw a growing cone from ongoing ash emissions. The Wellington VAAC noted that the eruption was short-lived and had stopped by 1548 when the ash had dissipated. During an overflight on the afternoon of 31 January, gas-and-steam was observed rising from the ocean surface above Epi B, discolored water was visible around the eruption site, and pumice rafts were floating on the surface (figure 10). Several strands of pumice that drifted to the SW, NW, and N of Epi B were visible in Sentinel-2 satellite imagery on 2 and 14 February (figure 11). Gas-and-steam emissions were also visible at the surface for a few hours during 1 February. During 0700-1030 on 7 February residents observed minor, low-level gas-and-steam emissions above Epi B. The intensity of the gas-and-steam plumes varied, with stronger activity reported by local residents around 0600 on 8 February. On 23 February VMGD reported sustained seismicity and minor gas-and-steam plumes that only lasted a few hours.

Two main explosions were recorded by different monitoring networks, including seismic stations and the infrasound array located in Papua New Guinea (Figure 3). Although this had no apparent consequence on the nearby communities, a small tsunami was however reported by locals and recorded on the coastal tide gauges of Port-Vila to the South and Luganville to the North showing a maximum amplitude of ~5 cm. (reference #13679)

In the early months of 2023, an underwater eruption occurred at one of the East Epi volcanic cones, to the east of Epi Island, Vanuatu. On 31 January UTC (1 February LT), a large explosion was heard by locals at sunrise, some of them taking pictures of an eruption column rising above the sea, visually estimated to be ~ 100 m high. Despite the seismic activity and eruptive phenomena, it is noteworthy that this underwater eruption had no reported adverse effects on nearby communities (reference #14376)