Bagiai cone
Karkar Island is a complex stratovolcano about 30 km off the north coast of mainland Papua New Guinea. Early eruptive events produced the basic shape of the volcano, but caldera formation and Plinian and Peléean activity in the late Quarternary have modified the shape of the island. Five units of pyroclastic materials are found over most of Karkar. Two ignimbrite units were probably associated with the collapse that formed the outer caldera (the more recent of these is about 9000 years old). A unit of airfall tephras represents a period when the outer caldera was being filled by a volcano consisting of tephras and lavas. This was a relatively quiet period, but subsequent violent eruptions between 1500 and 800 years B.P. produced two more ignimbrite units, which were almost certainly associated with the collapse (or collapses) that formed the inner caldera of Karkar. Tephra has been erupted more recently over the whole island, and tephra and lava are gradually filling the inner caldera.
The latest eruptions at Karkar occurred in 1974-1975 and 1979. On both occasions the eruptions originated from Bagiai cone located slightly west from the center of the inner caldera. During the 1974-1975 eruption a significant volume of lava was erupted. The lava filed from the eruption encircled Bagiai cone and covered almost 70 percent of the floor of the inner caldera. On the other hand, the eruption in 1979 did not produce any lava flow. It was more explosive in character. One of these explosions on 8th March killed two volcanologists from the Rabaul Volcanological Observatory at their observation campsite on the south-southwest rim of the inner caldera. The debris from the explosion obliterated about half of the lava field emplaced during the 1974-1975 eruption.
In 1979 the population of Karkar Island was about 23,000. Today the population has almost doubled to about 42,000. The increase in population and associated growth in property ownership has increased the level of risk to greater levels than ever before. This and other factors, including the tenacity of eruptions Karkar is potential of producing makes it one of the six high-volcanoes in PNG. The others include Rabaul, Manam, Ulawun, Lamington and Pago.
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