Ulawun is one of the most active volcanos in Papua- New Guinea and is one of the most dangerous volcanos of that place. It is the highest volcano in the 1000 km long Bismarck volcanic stretching from Rabaul to Wewak. Ulawun volcano is composed of lava flows with tephra composed of basalt and andesite.
Ulawun activity includes Strombolian and Pelean eruptions. Eruptions originate from a central crater. The eruption of Ulawun was in 1700. The next record was 178 years later. A large eruption in 1915 deposited about 10 cm of ash at Toriu, 50 km northeast of the volcano. In 1970, a large eruption produced massive quantity of lava flows. The eruption devastated the north western flank and modified the summit crater. An eruption in 1980 ejected ashes to 60,000 feet and produced pyroclastic flows which swept all the flanks of the volcano and devastated an area of 20 sq km. The most serious volcanic hazard at Ulawun volcano is catastrophic structural collapse. It produced an eruption which devastated hundreds of sq km in area. Ulawun volcano is 400 m higher than most of the volcanoes in the Bismarck which indicates it may be at the limit of structural stability. On 14th – 15th February 2010, ash emissions from Ulawun volcano reached a height of 3.7 km and drifted upto 95 km away.