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Long Island Volcano | Dr John Seach
Last updated: January 2026
Madang Province,
Papua New Guinea
5.36 S, 147.12 E
summit elevation 1280 m
Complex volcano (caldera)
Long Island is a large volcanic island (~30 x 21 km) located ~136 km east of Madang in the Vitiaz Strait. The island features a prominent caldera occupied by scenic Lake Wisdom (12 x 10 km, 150 m altitude). Post-caldera activity has formed Motmot Island in the lake centre. The volcano is capable of large explosive eruptions.
Warning: Long Island has produced one of the largest eruptions in the past 2000 years (~1660 AD, VEI 6). Although dormant since 1993, future large explosive activity could generate widespread ashfall, pyroclastic flows, and tsunamis. Access to the caldera lake area requires caution due to potential geothermal hazards.
Geology and Volcanology
Long Island is a basaltic-andesitic complex with a large caldera formed during the catastrophic ~1660 AD eruption. Post-caldera vents have produced intracaldera islands (e.g., Motmot) through Surtseyan and Strombolian activity. Weak solfataric manifestations persist. Monitoring by the Rabaul Volcano Observatory uses seismicity, satellite data, and occasional visits to detect unrest.
Current Activity (January 2026)
Long Island remains dormant with no significant activity since minor lake discolouration in 1993. Satellite observations show no thermal anomalies, gas plumes, or unrest. Occasional regional earthquakes are tectonic. The volcano is stable but monitored for potential reactivation.
Ongoing Dormancy (post-1993)
Minor lake water discolouration in 1993 possibly indicated weak hydrothermal disturbance.
20th Century Activity
Intermittent minor eruptions: 1973-1974 (crater glow), 1968 (ash cone formation), 1953-1955 (Surtseyan, Motmot Island formation), and earlier 1943, 1938, 1933 events.
1660 Great Eruption
Catastrophic caldera-forming Plinian eruption (VEI 6) ejected ~30 cubic km of material, producing widespread "Time of Darkness" tephra fall across New Guinea highlands (up to 1.5 cm thick over 87,000 sq km). One of the largest eruptions globally in the past 2000 years.
Further reading
Blong, R., Fallon, S., Wood, R., McKee, C., Chen, K., Magill, C. and Barter, P., 2018. Significance and timing of the mid-17th-century eruption of Long Island, Papua New Guinea. The Holocene, 28(4), pp.529-544.
Pain, C.F., Blong, R.J., McKee, C.O. and Polach, H.A., 1981. Pyroclastic deposits and eruptive sequences of Long Island. Cooke-Ravian volume of volcanological papers. Geological Survey of Papua New Guinea, Port Moresby, Memoir 10, pp.101-113.
Long Island Volcano Eruptions
1993 (minor lake disturbance), 1973-1974, 1968, 1953-1955 (Motmot Island formation), 1943, 1938, 1933, ~1660 (major caldera-forming)
Dormant since 1993