The Volcanoes of Vanuatu: Nine Active Cones on the Ring of Fire

Why there are so many

Vanuatu sits on the New Hebrides subduction zone, where one tectonic plate is forced beneath another. The descending plate releases water into the rock above, which lowers its melting point; the melt rises and builds volcanoes in a line along the boundary. The whole archipelago exists because of this process — see geography.

The active nine

Yasur

Tanna. Almost continuously active, and among the most accessible active volcanoes in the world.

Marum & Benbow

Ambrym. Two craters inside a caldera roughly 12 km across, with a history of lava lakes.

Lopevi

An uninhabited cone island between Ambrym and Epi, evacuated permanently after repeated eruptions.

Manaro Voui

Ambae. Its 2017–2018 activity forced the evacuation of the entire island population.

Mount Garet

Gaua, in the Banks group, rising from Lake Letas.

Suretamatai

Vanua Lava, Banks group.

Traitor’s Head

Erromango.

Epi submarine cones

East Epi, active below the sea surface.

The alert-level system

The Vanuatu Meteorology and Geo-hazards Department assigns each volcano a level from 0 to 5. Level 0 is normal. Level 2 means major unrest with danger near the crater. At higher levels an exclusion zone is declared and access is closed, including to tour operators. The levels change with activity and are published by the department.

Living with them

Volcanic ash damages gardens and water supplies long after an eruption stops, and ashfall rather than lava is usually what forces people to move. Ambae in 2017 is the clearest recent case: the whole island was evacuated, and the return was slow.

How a subduction volcano works

As the descending plate sinks it carries water locked into its minerals. At depth that water is released into the hot rock above, and water lowers the melting point of rock substantially. The resulting melt is less dense than its surroundings, rises, and collects in chambers beneath the surface. Eruption is what happens when the pressure in those chambers exceeds what the rock above can hold.

This is why subduction volcanoes tend to erupt explosively: the magma is viscous and carries dissolved gas that comes out of solution violently near the surface.

Ambae, 2017 and 2018

Manaro Voui produced sustained ashfall that contaminated water supplies and destroyed gardens across Ambae. The entire population — on the order of eleven thousand people — was evacuated to Santo, Maewo and Pentecost, some of them twice. It was the largest displacement in Vanuatu’s recent history and it was caused by ash, not lava.

Monitoring

The Vanuatu Meteorology and Geo-hazards Department runs seismic and visual monitoring and publishes alert levels and bulletins. Its decisions close and open access to the craters, including for tour operators, and they are not subject to negotiation.

Why people stay

Volcanic soil is fertile, and the same ash that destroys a garden in one year enriches it over decades. Communities on Ambrym and Tanna have lived with continuous activity for generations, and the calculation they make is not ignorance of the risk but familiarity with it.

Ash and aviation

Volcanic ash is a hazard to aircraft engines, and eruptions at Ambae, Ambrym and Yasur have all closed domestic routes and occasionally international ones. This is the most common way an eruption affects a visitor who is nowhere near the volcano: the flight does not go.

Watching one safely

Standing at a crater rim is only safe where the activity is predictable and the monitoring is current, which in Vanuatu means Yasur and only at permitted alert levels. Approaching any other active vent without guides and without checking the level is how people are injured, and the department publishes the levels precisely so that nobody has to guess.

Yasur as an outlier

Most active volcanoes are either too dangerous or too remote to visit. Yasur is neither: the crater is 360 metres above sea level, a track runs most of the way up, and the activity is strombolian — a sequence of discrete explosions. That combination is rare enough that volcanologists use it as a natural laboratory and tourists use it as an evening excursion.

Lopevi

A near-perfect cone rising 1,400 metres from the sea between Ambrym and Epi. It was inhabited until repeated eruptions through the twentieth century forced permanent evacuation, and it is now empty. It is among the most striking sights in the country precisely because nobody is on it.

Submarine activity

Not all of the volcanism is above water. The East Epi field has erupted within living memory, briefly building an island in the 1950s that the sea then removed. Discoloured water and floating pumice are the usual surface signs.