Long Island

Geography & Climate

Long Island is located in Papua New Guinea, within the Bismarck Volcanic Arc of the broader Southwestern Pacific Volcanic Regions. Situated at 5.31° S, 147.10° E in the Southern Hemisphere, the volcano lies within a tropical climate zone. With a summit elevation of 1,263 meters above sea level, Long Island is a moderately sized peak that remains accessible to hikers and researchers for much of the year. The volcanic landform is characterized as a composite, which describes the physical shape and structure of the volcanic edifice as observed from the surface.

Geological Context

Long Island sits in a subduction zone, where one tectonic plate dives beneath another, creating intense heat and pressure that generates magma. Subduction zones are responsible for many of the world's most explosive volcanoes and deadliest eruptions. For communities in Papua New Guinea near Long Island, this tectonic setting means the volcano is capable of producing powerful explosive eruptions, pyroclastic flows, and lahars that can threaten populated areas within tens of kilometers of the summit. The dominant rock type is andesite / basaltic andesite, a dark, fine-grained volcanic rock that forms from rapidly cooling, low-viscosity lava. Basaltic eruptions tend to be less explosive and produce fluid lava flows that can travel long distances. While less immediately dangerous than explosive eruptions, basaltic lava flows can destroy structures and infrastructure in their path, and volcanic gases released during these eruptions can affect air quality over a wide area.

Eruption History Summary

Long Island has 12 recorded eruptions in the geological database, spanning from 2040 BCE to 1993 CE. The most powerful recorded event was a colossal eruption capable of affecting global climate for years in 1660 CE, reaching VEI 6 on the Volcanic Explosivity Index. Notable eruptions include 1955 CE (VEI 3), 1953 CE (VEI 3), 1660 CE (VEI 6). This level of eruptive frequency indicates a persistently active volcanic system that warrants ongoing monitoring. The most recent eruption in 1993 CE places this volcano within the modern era of volcanological observation.

Significance

Long Island has produced at least one eruption of VEI 6 or higher, placing it among the most powerful volcanic systems on Earth. Eruptions of this magnitude inject massive quantities of sulfur dioxide into the stratosphere, affecting global climate by lowering average temperatures for one to three years after the event. With 12 recorded eruptions, Long Island has a substantial eruptive history that provides valuable data for understanding volcanic behavior and assessing future hazards in the Southwestern Pacific Volcanic Regions region. Given its recent activity, Long Island is closely monitored by geological survey organizations to provide early warning of future unrest.

GVP Reference Summary

The broad profile of Long Island is dominated by two steep-sided stratovolcanoes, Mount Reaumur in the north and Cerisy Peak in the south. Collapse of the basaltic-andesitic volcanic complex produced a large 10 x 12.5 km caldera, now filled by Lake Wisdom. Caldera formation occurred during at least three major explosive eruptions, about 16,000, 4,000, and 300 years ago. The most recent deposited andesitic tephra across the New Guinea Highlands, prompting legends of a "Time of Darkness." Post-caldera eruptions have constructed a small cone, Motmot Island, in the south-central part of Lake Wisdom. Moderate explosive eruptions have occurred during the 20th century from vents at and near Motmot Island.

— Smithsonian Institution, Global Volcanism Program