In early January 1951, a series of minor explosions and earthquakes rocked Mount Lamington, a volcano in the Australian-administered Territory of Papua and New Guinea (now in Oro Province, Papua New Guinea). Prior to the eruption, Mount Lamington was not recognized as a volcano due to the absence of historically recorded eruptions and dense vegetation cover. From January 15, volcanic activity intensified, and tall eruption plumes were generated. The largest eruption occurred on the morning of January 21 when a thick black plume of ash rose into the atmosphere. The eruption collapsed a lava dome and produced a lethal pyroclastic flow that killed 2,942 people. In the years after the eruption, new lava domes formed and collapsed in succession. Activity persisted until July 1956. The eruption is the deadliest natural disaster in Australian history, as the region was under the rule of the Government of Australia.
Tectonic setting Volcanism in Papua New Guinea is due to the ongoing subduction of oceanic crust beneath the island due to plate tectonics. Mount Lamington is situated within the Hydrographers Range; a small, forested coastal mountain range. The mountain range is the remnant of a heavily eroded Quaternary stratovolcano. The dominant rock types are andesite and basaltic andesite. While a majority of the range's eruptive history occurred during the Pleistocene, the presence of cinder cones and craters on the southern flank of the range suggest volcanism also took place during the Holocene. The mountain lies adjacent to the Owen Stanley Range. Nearby volcanoes include Mount Suckling and Mount Victory.
Volcanology
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 prominent broad "avalanche valley" extends northward from the breached crater. The horseshoe-shaped crater was the result of a large sector collapse. It occurred about 20,000 years Before Present, when the volcano was approximately high. A section of the volcanic cone, estimated to be , was destroyed by the collapse during this prehistoric eruption.
Prior to the eruption in 1951, locals did not know that Mount Lamington is an active volcano as the native population had no widespread ancient folklore or stories of activity. The only indication of volcanic activity was a small hot spring on the northern slopes, which most of the native population did not know about. 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. There were some settlements on the flank of the volcano, and the native population regards the mountain as a sacred and spiritual place.
Geologists however, understood that Mount Lamington and the Hydrographers Range are volcanic in origin, and that it was a geologically young feature. Reinout Willem van Bemmelen, a geologist from the Netherlands classified Mount Lamington an active volcano. Only three eruptions were confirmed in the Holocene.
Events
Pre–January 21 activity Several inhabitants around Mount Lamington reported earthquakes in early January 1951, and on January 15, there were signs of landslides in the crater wall including streaks of brown in the heavily forested flank. At a rubber plantation in Sangara village, a person reported white smoke or vapour cloud rising from the base of the volcano. Around the crater, vegetation was killed by the intense heat emitted from the ground.
On January 16, a vapour cloud was observed from Higaturu. Large landslides were reported, many destroying the existing vegetation. The entire rainforest around the crater was destroyed by the late afternoon. An earthquake swarm occurred at 16:00. Up to 30 earthquakes were felt till 08:00 on January 17. Stronger earthquakes were felt in Isivita Mission, located northwest of the crater.
On January 17, an ash column rising between some hills and Mount Lamington was observed. The column grew larger as the hours passed. Earthquakes continued to be felt, and there was a red glow observed at night. By January 18, large plumes of dark grey ash ejected from the volcano, and a newly constructed volcanic hill appeared where debris was ejected. According to District Commissioner Cecil Cowley on January 19, these eruptions did not cause fatalities. It generated large columns of ash rising . On 20 January, the eruption generated a column. From Kokoda, it was described as a large black column with shaped similar to a cauliflower. Heavy ashfall occurred on the southern side of the volcano because of the monsoon winds, damaging some Orokaiva settlements.
January 21 eruption
The most violent eruption occurred four days later at 10:40 local time. Occupants on two Qantas Empire Airways flights which flew in close proximity to the erupting volcano reported a large eruption column and base surge of pyroclastic debris. The captain of a Douglas DC-3 flight witnessed a massive continuous column of black smoke erupting from the crater. The column rose over , punching through a layer of clouds. In two minutes, the column had risen from the crater, and expanded into a mushroom column. The eruption column reached at its highest. The captain of the DC-3 radioed authorities at Port Moresby about the sequence of events. 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 large surge of debris approached the aircraft, forcing its return to Lae.
Changing winds directed the pyroclastic surge northeast, where it was seen at Kokoda. Lightning was observed in the eruption column. Ash, pumice and small rocks fell to the ground. The eruption column was also observed at Eroro, where many residents mistook it for a petrol explosion at Higaturu. A large pyroclastic surge raced towards Isivita Mission; northwest of the crater. Many panicked residents rushed to the main mission house. The flow, however, ceased in the mission compound. A definitive boundary between the grassy field and thick layer of volcanic material marked the trail of the flow. By 11:30, the eruption column had blocked sunlight. Thunder was heard, and intense lightning was observed.
Awala Plantation near Isivita Mission was spared the worst of the eruption but suffered from extensive ash fall. Much of the rubber, coffee and cocoa crops were devastated. The loss of crops had implications for the local economy. The eruption seriously affected the fish population in rivers. The local population experienced a decline in the aftermath of the eruption. Rainforests were also covered in thick layers of ash, and trees began to topple or break apart due to the weight of ash. Overnight, 18 people perished at Isivita. Higaturu, another town slightly further away, was totally destroyed.
By the afternoon, many residents with extreme burns from the pyroclastic flow were rescued. Many began to arrive at treatment centers for medical assistance. Survivors described the sounds of agony from burn victims. Some victims experienced total burns to their skins. One burn victim later died. More deaths were anticipated following the eruption, so a large grave was dug. There was a large inflow of seriously burnt victims at the Sangara Plantation. Injured victims were also transported to Popondetta.
The destruction was described as "complete" and comparisons were drawn with a bomb explosion. Trees in the dense tropical rainforest toppled or were pulverized. Nearly every building was destroyed by the flow. The region surrounding Mount Lamington was transformed into a moonscape-like environment. Charred bodies of people attempting to flee the surging flow littered the roads.
Post–January 21 activity The post–January 21 eruptive phase consisted of explosive eruptions which produced pyroclastic flows. A large pyroclastic flow was documented on March 5, 1951. After the climactic eruption on January 21, a new lava dome formed in the crater. The new lava dome grew to fill the crater. From 1951 to 1953, new lava domes formed and collapsed, generating more pyroclastic flows. The dome eventually attained a height of 450 meters from the crater floor to its summit and had a volume of . A lava spine emerged from the dome and grew to a height of . Lava spines continuously formed and were destroyed over a five-year period.
Scientific study and monitoring
The eruption rated a four on the Volcanic Explosivity Index scale of zero to eight. This vertical eruption blast was accompanied by a lateral collapse of the volcano flank. At the time of the eruption, volcanologist Tony Taylor was studying the Rabaul caldera, another volcano in Papua New Guinea. He arrived one day after the eruption. Taylor conducted a dangerous on-site investigation to determine the probability of another eruption, including a flight over the erupting crater.
Mount Lamington was continuously monitored due to the potential for future eruptions. Taylor spent two years studying the volcano, where he received support from the Bureau of Mineral Resources, Geology and Geophysics (BMR). Seismologist Bill Langron and geologist John Best also assisted in the scientific study. A de Havilland Mosquito of the No. 87 Squadron RAAF conducted a reconnaissance flight in the affected area. Photographs taken during the flight were used in mapping the devastation's reach and change in topography around Mount Lamington. There were concerns of an imminent eruption of Mount Victory, another volcano near Tufi and Wanigela. An inspection of the volcano suggest there was no threat.
Taylor interpreted that the landslides initially observed were the result of the earthquake swarm or other geological processes. Intense activity occurred in the subsequent days after, including an interpreted Vulcanian eruption on 17 January. That eruption was caused by magma interacting with groundwater. The young hill structure observed via a telescope and initially interpreted by Taylor as a pile of debris, was instead a small lava dome.
The large volume of volcanic ash and debris ejected vertically into the atmosphere on 21 January was a Plinian-style eruption. This triggered a debris avalanche with an estimated volume of which traveled . The eruption column formed a large mushroom cloud towering over the summit. Pyroclastic flows surged down the flank of the volcano as the eruption column collapsed. The thick and dense cloud of black ash was described as "like toothpaste from a tube". An approximately area of dense tropical rainforest around Mount Lamington was devastated.
The pyroclastic flows moved with such velocity, about per hour, that no humans in the areas of devastation survived. Extreme damage occurred within a radius around the volcano. It traveled northwards for due to the influence of the breached, horseshoe-shaped crater in the north. A second eruption occurred at 19:30, generating an ash cloud almost identical in height as the daytime eruption. This eruption produced a loud sound and heavy ashfall, although no pyroclastic flows were reported.