Report on Manam (Papua New Guinea) — March 1983
Scientific Event Alert Network Bulletin, vol. 8, no. 3 (March 1983)
Managing Editor: Lindsay McClelland.
Manam (Papua New Guinea) Explosions, ash emissions, and seismicity increase
Please cite this report as:
Global Volcanism Program, 1983. Report on Manam (Papua New Guinea). In: McClelland, L. (ed.), Scientific Event Alert Network Bulletin, 8:3. Smithsonian Institution. https://doi.org/10.5479/si.GVP.SEAN198303-251020.
Papua New Guinea
4.08°S, 145.037°E; summit elev. 1807 m
All times are local (unless otherwise noted)
"Southern crater became more active in March after showing increasing activity in late February. Weak explosion sounds were heard on most days until 14 March, accompanying weak to moderate white-grey vapour and ash emissions. Weak ejections were reported on 12 and 13 March, when weak crater glow was seen. A period of somewhat stronger emissions was reported 19-24 March, including low to moderate explosion sounds on 23 and 24 March, and continuous vapour and ash emissions were noted on 26 and 29 March. Weak rumbling was heard from the 29th to the month's end, and deep booming sounds were reported on the 31st.
"Generally steady activity of weak to moderate white-grey emissions occurred at Main crater until about 23 March. These emissions were usually not accompanied by sound effects, but on 2 and 3 March weak explosion sounds were heard. From the 24th to the end of the month emissions were reported to be moderate, and included brown ash from the 27th. Light ashfalls were reported on about 30% of days from locations on the E and SE flanks.
"A steady increase in the daily number of volcanic earthquakes took place in March, from about 1200 at the beginning of the month to about 2100 at month's end. Event amplitudes showed a slight stepwise increase at mid-month. A marked brief increase in seismic amplitudes was also noted on 4 and 5 March.
"Tilt measurements showed steady changes of about 1 µrad down to the NW from the observatory, on the SW flank (figure 1)."
Geologic Background. The 10-km-wide island of Manam, lying 13 km off the northern coast of mainland Papua New Guinea, is one of the country's most active volcanoes. Four large radial valleys extend from the unvegetated summit of the conical 1807-m-high basaltic-andesitic stratovolcano to its lower flanks. These "avalanche valleys" channel lava flows and pyroclastic avalanches that have sometimes reached the coast. Five small satellitic centers are located near the island's shoreline on the northern, southern, and western sides. Two summit craters are present; both are active, although most historical eruptions have originated from the southern crater, concentrating eruptive products during much of the past century into the SE valley. Frequent historical eruptions, typically of mild-to-moderate scale, have been recorded since 1616. Occasional larger eruptions have produced pyroclastic flows and lava flows that reached flat-lying coastal areas and entered the sea, sometimes impacting populated areas.
Information Contacts: C. McKee, RVO.