Vanuatu's geography: an island arc built and shaken by one plate boundary

Where the island chain lies and how far

The archipelago runs between latitudes 13°S and 21°S and longitudes 166°E and 171°E, about 1,750 kilometres east of northern Australia and 540 kilometres north-east of New Caledonia. Its islands form a Y about 1,300 kilometres from the Torres and Banks Islands in the north to Aneityum in the south. Wikipedia's country article counts about 83 islands, 65 of them inhabited.

Fourteen islands cover more than 100 square kilometres each. In order of size they are Espiritu Santo, Malakula, Efate, Erromango, Ambrym, Tanna, Pentecost, Epi, Ambae, Gaua, Vanua Lava, Maewo, Malo and Aneityum. Espiritu Santo carries the highest point, Mount Tabwemasana, at 1,879 metres in Britannica's figure. Port Vila, the capital, lies on Efate, and Luganville, the second town, on Espiritu Santo.

Published areas for the whole country disagree by about 90 square kilometres. Britannica gives a total of 12,281 square kilometres and Wikipedia's country article 12,274, while the geography article, which follows the World Factbook, gives 12,189 with a coastline of 2,528 kilometres. Its exclusive economic zone is given as 663,251 square kilometres in the geography article and as 680,000 in Wikipedia's economy article.

Two uninhabited islands at the southern end of the arc, Matthew and Hunter, are claimed by Vanuatu and by France. Britannica records that Vanuatu claimed them in 1982 to extend its economic zone, that they lie about 250 kilometres south-east of Aneityum, and that France disputes the claim. Wikipedia describes them as controlled by France as part of New Caledonia. This catalogue records that the claim is disputed and takes no position on it.

Why the islands rise and shake

The chain is an island arc on the boundary between two plates. Oceanic crust of the Indo-Australian Plate is pushed east beneath the Pacific Plate, and the pressure lifts parts of the islands by up to 2 centimetres a year, raising old coral reefs into terraces above the shore. Most of the islands are steep, with unstable soils and little permanent fresh water, and the shoreline is mostly rocky, edged by fringing reefs and dropping quickly to deep water.

Earthquakes are frequent. Wikipedia counts 58 events of magnitude 7 or more between 1909 and 2001, few of them studied. An earthquake and tsunami in November 1999 left thousands homeless on Pentecost. On 3 January 2002 a magnitude 7.2 earthquake caused landslides in Port Vila and damaged buildings and bridges without killing anyone, according to the Global Volcanism Program, and Yasur's activity rose in the following days. Another of magnitude 7.2 struck on 2 August 2007.

The most recent large earthquake struck Efate in December 2024. An earthquake of magnitude 7.3 reportedly damaged almost every house on the island and killed 19 people. The United Nations Office for the Coordination of Humanitarian Affairs estimated that it directly affected 116,000 people, about a third of the population.

The Australian geologist Douglas Mawson made the first geological survey of the group from April to September 1903, and his report of 1905 included the first geological maps of Efate and south-west Santo. He described the raised reefs of Santo but could not land on Tanna to see Yasur.

Which volcanoes are erupting

Britannica names active volcanoes on Vanua Lava, Ambae, Gaua, Ambrym and Tanna, several submarine vents, and solfataras and fumaroles on some islands. The Vanuatu Meteorology and Geohazards Department sets an alert level for each, on a scale on which level 1 means signs of unrest and level 2 major unrest.

How Yasur on Tanna erupts

Yasur rises to 361 metres near Sulphur Bay on the south-east of Tanna. It is a largely bare cone of ash and cinders around a summit crater about 400 metres across, set inside the small Yenkahe caldera. The Global Volcanism Program describes an eruption that has run since at least 1774, when James Cook saw its fire, made up of Strombolian explosions that throw out lava bombs and of ash and gas emissions. Wikipedia's article on the volcano says the explosions often come several times an hour.

The activity varies. From October 2013 the volcano grew more violent; ash damaged vegetation across Tanna and fell on Erromango, 150 kilometres to the north, and on 3 November 2013 explosions threw bombs up to 4 metres across as far as 250 metres from the vent. In its bulletin of 27 March 2025 the geohazards department kept the danger zone at a radius of 600 metres from the vents and warned that villages downwind would continue to receive ash and acid rain. The International Union of Geological Sciences listed the Yasur and Yenkahe volcanic complex among 100 geological heritage sites in October 2022.

The name comes from iasur, the word for volcano in Kwamera, a language of south-east Tanna. The mountain is also sacred ground for the John Frum movement, whose members hold that John Frum lives inside it, and the village of Sulphur Bay, the movement's centre, claims the volcano as part of its territory. A lava plain spreads across the valley at the foot of the cone.

What the other volcanoes are doing

Ambrym holds the twin vents of Benbow and Marum. A large eruption there about 200 CE would have devastated the people living there and probably set off movements of population to other islands. On Ambae, Manaro Voui stood at level 3 in October 2026. East of Epi a submarine volcano has been at level 1 since 1 February 2023; the department warns boats to stay 2 kilometres from its vents and expects floating pumice along the coasts of Epi and the islands near it. Wikipedia's geography article adds to the list of potentially active centres Kuwae, a submarine volcano, and Traitor's Head on Erromango, and its country article records an undersea eruption nearby in November 2008 that caused no casualties.

On Gaua the cone of Mount Garet stands beside Lake Letas, a crater lake, in a photograph Britannica publishes of the island. Lopevi, a volcano that forms an island of its own, carried level 2 in October 2026. Tsunamis are a hazard with both the earthquakes and the volcanoes, and the earthquakes of 1999 and 2002 were each followed by one.

How the rain divides the north from the south

The climate is tropical, with two seasons. Britannica describes a hot, wet season from November to April and a cooler, drier one from May to October, when the south-east trade winds blow steadily. Northerly winds in the hot season bring most of the heavy rain. The total rises from south to north: about 2,000 millimetres a year in the southern islands and some 4,000 millimetres in the northern ones, in Britannica's figures. Wikipedia gives an average of about 2,360 millimetres for the country as a whole.

Temperatures change less than rain. Wikipedia's geography article classes the climate as tropical rainforest, Af in the Köppen system, kept from being equatorial by the nearly permanent trade winds and the cyclones. Daily temperatures run from about 20 to 32 °C, and the sea from about 22 °C in winter to 28 °C in summer. The wettest and hottest months, December to April, are also the cyclone season.

What cyclones have done to the islands

Tropical Cyclone Pam crossed Vanuatu between 12 and 14 March 2015 as a Category 5 storm, with sustained winds estimated at 250 kilometres an hour and gusts of around 320. Its centre passed east of Efate and then just west of Erromango and Tanna, and the damage was worst on those three islands. The government's post-disaster needs assessment confirmed eleven deaths in Tafea and Shefa provinces, an estimated 65,000 people displaced and about 17,000 buildings damaged or destroyed; Wikipedia's country article gives 16 deaths. Crops were destroyed on a large scale, affecting the livelihoods of at least 80% of the rural population.

Cyclone Harold passed through Luganville on Espiritu Santo in April 2020 and caused heavy damage there and on at least four islands. The International Monetary Fund counts three cyclones in 2023 among the shocks to the economy.

Where people live on steep islands

The shape of the land decides where people settle. Narrow coastal plains and raised coral terraces carry most of the villages, and Britannica notes that on most islands unpaved roads link the coastal settlements while few roads cross the interior. Travel between islands goes by boat or by air. Roughly three-quarters of the population lives in rural areas, in Britannica's description, and Wikipedia's geography article puts the urban share at about 26%, most of it in Port Vila and Luganville.

The six provinces take their names from the initial letters of the islands they hold: Torba for the Torres and Banks Islands, Sanma for Santo and Malo, Penama for Pentecost, Ambae and Maewo, Malampa for Malakula, Ambrym and Paama, Shefa for the Shepherd group and Efate, and Tafea for Tanna, Aniwa, Futuna, Erromango and Aneityum. Futuna and Aniwa in the south and some other outlying islands have Polynesian populations.

Fresh water is the constraint that follows the people. Most islands have little permanent surface water, upland watersheds are being cleared, and Wikipedia's geography article lists water pollution, a limited supply of drinking water in rural areas and poor sanitation among the environmental concerns. Waste disposal and pollution have become problems around the towns and large villages. In 2018 Vanuatu banned plastic bags and plastic straws, and in 2020 it banned seven further types of single-use item, among them cutlery and plates.

What grows on steep volcanic ground

Dense rainforest covers much of the group, and drier areas carry patches of savanna grassland. The islands form their own ecoregion, the Vanuatu rain forests, part of the Australasian realm. Land suitable for farming is scarce on such slopes: an estimate from 2005 put agricultural use at about 9% of the land, and Wikipedia's geography article gives arable land as 1.6% of the area in 2022. Logging, shifting cultivation, coconut plantations and cattle ranches have all cleared forest, and erosion and landslides have increased on cleared slopes.

Animal life on land is sparse and bird and insect life abundant. Britannica counts about ten kinds of bat, three of them found only in Vanuatu; Wikipedia gives eleven species, three of them endemic, among them the flying fox Pteropus anetianus, which pollinates and spreads the seed of forest trees. Wikipedia also lists eight endemic reptiles and sixty-one species of land and water birds. Three or possibly four saltwater crocodiles live in the mangroves, said to have reached the northern islands after cyclones, with no breeding population.

The sea is richer. More than 4,000 species of marine molluscs live in the surrounding waters, and Wikipedia's country article records that 90% of households fish and eat fish, which has thinned stocks near villages. Cone snails and stonefish in the same waters carry venom that can kill a person. On land, the giant African land snail arrived only in the 1970s and has spread from the Port Vila area to Luganville, and the larger rat species came with Europeans, while the small Polynesian rat is thought to be indigenous.