The Rabaul Volcanological Observatory stated that the Strombolian eruption from Manam's S crater on 20 May ceased on the same day at about 1400. After that, activity consisted of forceful ash emissions in moderate volumes. The decline in activity led to the reduction in Alert Level from 2 ("eruption expected within weeks to months") to 1 ("non-threatening, background level"). According to the Darwin VAAC, the ash cloud produced from the 20 May eruption was no longer visible on satellite imagery by 22 May at 1515. People were reminded to be cautious when near the valleys SE and SW of the volcano.

Geological Summary. 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 basaltic-andesitic stratovolcano to its lower flanks. These 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 observed eruptions have originated from the southern crater, concentrating eruptive products during much of the past century into the SE valley. Frequent 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.

Sources: Rabaul Volcano Observatory (RVO), Darwin Volcanic Ash Advisory Centre (VAAC)