Significance and timing of the mid-17th-century eruption of Long Island,Papua New Guinea

Abstract

Tibito Tephra was first recorded in the central highlands of Papua New Guinea (PNG) in 1971. By the late 1970s, the tephra had been mapped across tens of thousands of square kilometres, traced to its source on Long Island in the Bismarck Sea, and linked to pyroclastic density currents in the Matapun Beds on the island. With a tephra fall volume >10 km³, this eruption was clearly one of the 10 largest globally in the past 600 years. Although almost certainly in the AD 17th or 18th centuries, determining just when this VEI 6 eruption occurred has proved difficult. Whether this eruption occurred before or after William Dampier sailed past, named, described and drew a profile of Long Island has been debated also. Dating the Long Island eruption has implications for assessing the rate of revegetation of the island, recolonisation of the island and caldera lake, Jared Diamond’s theory of ‘supertramp’ birds, correlations between major eruptions and ice core chronologies, the constant rate of supply model of ²¹⁰Pb concentration in lake sediments, reservoir effects in Lake Kutubu in the southern highlands of PNG, the timing of a prehistoric phase of agriculture in the Western Highlands and the longevity of oral histories recording a taim tudak (time of darkness) when sand fell from the sky, houses collapsed, crops were ruined and people died. This paper reviews early dates based on radiocarbon, ²¹⁰Pb and paleosecular magnetic variation, historical reports and genealogical dates from oral histories, and speculation based on tree ring and ice core evidence. Analyses of 10 new radiocarbon dates from the Matapun Beds on Long Island are reported. Our best estimate places the eruption between 1651 and 1671 AD with a 95.4% probability and between 1655 and 1665 AD with a 68.2% probability.