Mount Yasur
Interesting facts
- Near the crater rim stands what Vanuatu Post calls the world's only post box at an active volcano, and its mail receives a special Volcano Post cancellation.
- Next to Yasur, the Yenkahe block has risen by an average of about 156 millimetres a year over the past millennium, one of the fastest caldera uplifts known.
- Coral reef terraces that formed at sea level about 1,000 years ago now sit more than 150 metres above the sea on the uplifted Yenkahe block.
- Yasur grew inside the Siwi caldera, a basin about 4 kilometres wide left by an earlier, far larger explosive eruption.
- The crater floor holds three active vents, which take turns throwing out the glowing fragments seen from the rim.
- Geologists estimate the volcano has been in a near-constant state of eruption for roughly 800 years.
- Its lava is basaltic trachyandesite, and in 1920 a lava flow spread across part of the Siwi caldera.
- The name comes from 'iasur', a word for volcano in Kwamera, one of the languages of Tanna.
Why it is worth it
Few volcanoes let you stand on the rim and watch them work, and Yasur on the island of Tanna is the rare one that does it several times an hour. The cone is modest — just 361 metres above the sea — a bare, grey pyroclastic hill rising from a plain of ash near Sulphur Bay on the island's south-east side. What makes it extraordinary is its temperament: it has been erupting almost without pause for centuries, tossing incandescent bombs out of a near-circular crater about 400 metres across in a rhythm of Strombolian bursts and heavier Vulcanian blasts.
The volcano sits on the Vanuatu subduction zone, where the Indo-Australian Plate dives eastward under the Pacific Plate, and that steady supply of magma is why the glow never really goes out. The glow has a place in history too: it is thought to be what drew James Cook towards Tanna in 1774, on the first European visit to the island, and its reputation as the "lighthouse of the Pacific" comes from the same beacon seen from the sea. In 2022 Yasur was named among the IUGS Geological Heritage Sites.
For the people of Tanna the mountain is not scenery but a sacred place. The village of Sulphur Bay, the heart of the John Frum movement, regards the volcano as its own, and followers hold that John Frum lives inside it. The best time to be at the rim is dusk, when the ash landscape turns violet and each explosion paints the underside of the steam cloud orange; the thud of an eruption arrives a moment before the fragments arc overhead and fall back into the pit. Activity is watched by the Vanuatu Geo-Hazards Observatory on an alert scale from 0 to 5, and visits are guided.
Getting there
Yasur is on Tanna, about 230 km from Port-Vila on Efate. Tanna is reached by a short domestic flight from Port-Vila to Whitegrass Airport (TAH), which lies near Lenakel on the west coast, about 24 km from the volcano in a straight line. From the Lenakel and Whitegrass side the drive across the island by 4x4, over dirt roads and the ash plain, takes about an hour and a half. Tours usually drive to a point just below the rim, leaving a short, steep walk of around ten minutes to the edge; since the viewing is at sunset, plan at least one night on the island.
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From the encyclopaedia
Mount Yasur is an active volcano on Tanna Island, Vanuatu, 361 m (1,184 ft) high above sea level, on the coast near Sulphur Bay, northeast of the taller Mount Tukosmera, which was active in the Pleistocene. It has a largely unvegetated pyroclastic cone with a nearly circular summit crater 400 m in diameter.
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