The active Yasur – Yenkahe volcanic complex


Yasur volcano

Yasur volcano within the Siwi caldera. The caldera margin marked as an escarpment north of Yasur. Left of Yasur resurgent lava domes form a ridge.

Geological Period


Main geological interest



Tanna Island, Vanuatu. SW Pacific.
19°31’45.0″S, 169°26’50.0″E

Yasur volcano within the Siwi caldera. The caldera margin marked as an escarpment north of Yasur. Left of Yasur resurgent lava domes form a ridge.

Erupting for more than 800 years, it is "the lighthouse of the Pacific”!

The Yasur – Yenkahe volcanic complex within the Siwi caldera is an excellent active site to study the diversity of volcanic processes and their eruptive products associated with a near-sea level mafic-intermediate arc volcano. The location provides graphic examples of welded to non-welded mafic ignimbrites and their proximal to distal facies variations. The Strombolian-style and phreatomagmatic explosive eruptions of Yasur can be observed with ease and safely. The caldera hosts a rapidly uplifting resurgent block and a fast-filling caldera demonstrating the dynamic processes associated with a modern caldera volcano.

Typical Strombolian-style explosive eruption observed during night from the crater rim of Yasur. (Copyright, Olivier Grunewald).

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).

Due to its easy access, Yasur volcano is a subject of volcanology research for over two decades and provides an excellent study site where theories can be tested by direct measurements and observations.

Digital Elevation Model of SE Tanna over a GoogleEarth satellite image, showing the Yasur cone (Y) and its 1920 lava flow within the Siwi caldera (orange line). Note the resurgent block, uplifted Holocene coral reef, and Ombus cone also marked within the caldera.

Allen, S.R. (2004) ‘Complex spatter- and pumice-rich pyroclastic deposits from an andesitic caldera-forming eruption: the Siwi pyroclastic sequence, Tanna, Vanuatu’, Bulletin of Volcanology, 67(1), pp. 27–41. Available at:

Brothelande, E. et al. (2016) ‘Insights into the evolution of the Yenkahe resurgent dome (Siwi caldera, Tanna Island, Vanuatu) inferred from aerial high-resolution photogrammetry’, Journal of Volcanology and Geothermal Research, 322, pp. 212–224. Available at:

Firth, C.W. et al. (2021) ‘Rapid magmatic processes drive persistently active volcanism’, Lithos, 380–381, p. 105868. Available at:

Spina, L. et al. (2016) ‘Explosive volcanic activity at Mt. Yasur: A characterization of the acoustic events (9–12th July 2011)’, Journal of Volcanology and Geothermal Research, 322, pp. 175–183. Available at:

Woitischek, J. et al. (2020) ‘Strombolian eruptions and dynamics of magma degassing at Yasur Volcano (Vanuatu)’, Journal of Volcanology and Geothermal Research, 398, p. 106869. Available at:

Károly Németh
Massey University, New Zealand; Institute of Earth Physics and Space Science, Hungary and Saudi Geological Survey, Kingdom of Saudi Arabia

Gary Lee
The Pacific Community (SPC), Fiji

Dana Tigarea
The Pacific Community (SPC), Fiji

Michel Leodoro
Ministry of Lands and Natural Resources, Vanuatu

Benjamin van Wyk de Vries
Université Clermont Auvergne, Laboratoire Magmas et Volcans, OPGC, CNRS et IRD, Clermont Ferrand, France