The largest eruption occurred on the morning of January 21 when a thick black plume of ash rose 15,000 metres (50,000 ft) into the atmosphere.

[2] Mount Lamington rises to a height of 1,680 meters above the coastal flats north of the Owen Stanley Range.

A summit complex of lava domes and crater remnants rises above a low-angle base of volcaniclastic deposits that are dissected by radial valleys.

A 1,060-metre (3,480 ft) section of the volcanic cone, estimated to be 0.47 cubic kilometres (0.11 cu mi), was destroyed by the collapse during this prehistoric eruption.

[2] A weak hint of its volcanic nature was a traditional story, related to the volcano's activity, of a lake on the summit which exploded, destroying villages and killing many people.

[5][6] Geologists however, understood that Mount Lamington and the Hydrographers Range are volcanic in origin, and that it was a geologically young feature.

At a rubber plantation in Sangara village, a person reported white smoke or vapour cloud rising from the base of the volcano.

Heavy ashfall occurred on the southern side of the volcano because of the monsoon winds, damaging some Orokaiva settlements.

The captain of a Douglas DC-3 flight witnessed a massive continuous column of black smoke erupting from the crater.

Another Qantas flight; a de Havilland Dragon bound for Popondetta from Lae, was about to land when its occupants witnessed the side of volcano blow itself apart.

A definitive boundary between the grassy field and thick layer of volcanic material marked the trail of the flow.

[12] Awala Plantation near Isivita Mission was spared the worst of the eruption but suffered from extensive ash fall.

The dome eventually attained a height of 450 meters from the crater floor to its summit and had a volume of 0.2 km3 (0.048 cu mi).

[4] At the time of the eruption, volcanologist Tony Taylor was studying the Rabaul caldera, another volcano in Papua New Guinea.

Taylor spent two years studying the volcano, where he received support from the Bureau of Mineral Resources, Geology and Geophysics (BMR).

The young hill structure observed via a telescope and initially interpreted by Taylor as a pile of debris, was instead a small lava dome.

[4] The large volume of volcanic ash and debris ejected vertically into the atmosphere on 21 January was a Plinian-style eruption.

[4] The pyroclastic flows moved with such velocity, about 135 km (84 mi) per hour, that no humans in the areas of devastation survived.

A previously straight steel pole on the hospital was severely bent in two places, and one side was eroded by the dense cloud.

An administration official in the city investigated the local population from August to October and concluded that 2,942 people died,[20] including 35 Australian expatriates missing and presumed dead.

[20] Victims caught in the pyroclastic flows suffered swollen, exfoliation and hemorrhage in their respiratory system after ingesting hot volcanic material.

[19] At refugee centers, poor hygiene led to health issues; three people eventually died, including a child who succumbed to pneumonia.

Volcanologist Tony Taylor said despite the intense activity leading up to the eruption, authorities were incapable of interpreting them as warning signs and managing the crisis.

[25] An undamaged road linking Gona to Kokoda which ran north of Mount Lamington served an important role in the rescue and recovery process.

The Australian Red Cross also donated blood plasma for injured victims, and food, medical supplies and other basic needs.

[14] Two mass burials and memorial services were held in the days immediately aftermath of the eruption, with an Anglican minister and Catholic priest cooperating on each, overlooking the devastation.

[26] An evacuation site at Wairopi was formed within days of the eruption on the floodplain of the Kumusi River, along a road that linked Kokoda and Popondetta.

The Mamama River, its main tributary, carried large quantities of debris from the southern flanks of Mount Lamington.

The severely-damaged coffee and rubber tree plantations regrew and were eventually sufficient to sustain the native population.

Root vegetables including yam and sweet potato, and banana plants started to grow two months later.