The active Yasur – Yenkahe volcanic complex

The Yasur–Yenkahe volcanic complex is hosted within the Siwi caldera in the SE sector of Tanna Island, which is part of the central volcanic chain of Vanuatu (Allen, 2004). The Siwi caldera (9×4 km) is delimited by the “Siwi Ring Fracture” (Allen, 2004). The resurgent intra-caldera Yenkahe block (6×3 km) is composed of up to 20,000 year old magmatic intrusions (Brothelande et al., 2016; Firth et al., 2021). Coral reef terraces dated at 1000 years BP are found today at altitudes more than 150 m high, which implies a mean uplift rate of 156 mm/year over the last millennium. Hence, this site is one of the faster caldera floor resurgences in the world. Yasur is a persistently active basaltic trachy-andesite volcano (361 m high and 1500 m wide) located within the Siwi caldera (Spina et al., 2016). In a near-constant state of eruption for approximately 800 years, giving the site its nickname “the lighthouse of the Pacific”. It has a 400 m wide crater, with three active vents located at the summit. Explosions described at Yasur suggest the occurrence of Strombolian-type eruptions with intermittent phreatomagmatic events (Woitischek et al., 2020).