Marum is one of the two active volcanoes inside Ambrym's vast summit caldera — a collapsed cone roughly 12 km across, filled with ash plains and scarred by lava flows. Marum and its neighbour Benbow are among the most accessible active lava lakes in the world, which makes Ambrym a serious destination for volcano enthusiasts.
The hike to Marum from the western villages typically takes 5–8 hours return, depending on starting point and current conditions. The route crosses the ash plain of the caldera floor — a genuinely otherworldly landscape of grey ash, fumaroles, and occasional sulphur vents — before ascending the flanks of the cone to the crater rim. Activity levels vary: when the lava lake is high and accessible, the spectacle is extraordinary; when gas levels are dangerous, guides will turn back.
A local guide is essential — not optional. Conditions change rapidly, the ash plain offers no landmarks, and guides know which routes are currently safe. Several villages on the island's rim organise treks, with Craig Cove and Ranon on the west coast being the usual starting points.