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[U09-P22] The escalating eruptive sequence of the 2021-2022 eruption of Hunga Tonga - Hunga Ha’apai
Keywords:HungaTonga, large eruption, eruption sequence, caldera-forming eruption
Predicting the sequential progression of a volcanic eruption, together with its exact timing of the onset, is the greatest challenge in mitigating volcanic disasters. We GSJ-AIST researchers aim to find patterns in the progression by analysing how past volcanic eruptions unfolded. The Eruption Sequence Database (ESDB) we built specifically contains large explosive volcanic eruptions in historical time with their sequence of events well documented. Based on 20 volcanic eruptions that we have already compiled, they can be divided into three types - Waning-type: Maximum eruption intensity at the beginning of the eruption; Multipeak-type: Intermittent eruptions of the same magnitude; Escalating-type: Maximum eruption intensity at the late stage of the eruption. The “Escalating-type” is found particularly significant in terms of disaster mitigation because it includes many of the largest explosive eruptions in human history, such as Pinatubo 1991, Quizapu 1932, and Krakatau 1883. It is hence imperative to detect such escalating eruptions before getting escalated.
The eruption of Hunga Tonga-Hunga Ha’apai in 2021-2022 was a series of activities for approximately 30 days. The activity includes a relatively strong eruption on 20 December (UTC), a strong eruption on 14 January, and an exceptionally strong eruption on 15 January. There was nothing abnormal in terms of both seismicity and seawater discolouration before 20 December. The first eruption on the 20th built a pyroclastic cone at the northern part of the caldera as well as relatively small pumice rafts in a few hours of high-intensity eruption. The activity then gradually decreased over time and turned to weak and intermittent Surtseyan activity around the 25th. The eruption on 14 January was larger than the first eruption and continued for the whole day. The renewed activity destroyed the pyroclastic cone which was built earlier. The climax eruption was started on 15 January with exceptionally strong intensity as its eruption column exceeded 50 km of altitude. The intensity quickly decreased after the initial 1 hour but sustained a significant level over the next 10~20 hours before the end of the eruption. A large seismic activity started on 16 January after the climax eruption. The intensity peaked on the 18th and then gradually waned over the next one month. We classified the eruption as an Escalating-type eruption in our Eruption Sequence Database because it had a climax at the late stage of the eruption.
An event strikingly similar to the Hunga Tonga eruption is Krakatau 1883 eruption. Both events had started with a relatively strong eruption from a volcanic island. The initial eruptions produced pumice fall deposits as well as pumice rafts. Then a relative quiescence with a series of small intermittent eruptions followed the onset. The duration of the quiescences were 90 days for Krakatau 1883 and 25 days for Hunga Tonga 2021-2022. Such periods might be a preparation time for the following climax eruption in their magma plumbing system. The destruction of edifices started in the late stage of the quiescence in Krakatau and the later strong eruption in Hunga Tonga. This also might be an important preparation process in terms of structural instability. The climax eruptions in both events continued for almost a day with the generation of multiple waves of tsunami. Moreover, large seismic unrest which might be related to the caldera collapse similarly followed the climax eruption and continued for one month. The future research effort into the subaerial as well as the submarine part of the Hunga Tonga volcano will provide essential insights into such rare but extremely dangerous escalating-type eruptions.
The eruption of Hunga Tonga-Hunga Ha’apai in 2021-2022 was a series of activities for approximately 30 days. The activity includes a relatively strong eruption on 20 December (UTC), a strong eruption on 14 January, and an exceptionally strong eruption on 15 January. There was nothing abnormal in terms of both seismicity and seawater discolouration before 20 December. The first eruption on the 20th built a pyroclastic cone at the northern part of the caldera as well as relatively small pumice rafts in a few hours of high-intensity eruption. The activity then gradually decreased over time and turned to weak and intermittent Surtseyan activity around the 25th. The eruption on 14 January was larger than the first eruption and continued for the whole day. The renewed activity destroyed the pyroclastic cone which was built earlier. The climax eruption was started on 15 January with exceptionally strong intensity as its eruption column exceeded 50 km of altitude. The intensity quickly decreased after the initial 1 hour but sustained a significant level over the next 10~20 hours before the end of the eruption. A large seismic activity started on 16 January after the climax eruption. The intensity peaked on the 18th and then gradually waned over the next one month. We classified the eruption as an Escalating-type eruption in our Eruption Sequence Database because it had a climax at the late stage of the eruption.
An event strikingly similar to the Hunga Tonga eruption is Krakatau 1883 eruption. Both events had started with a relatively strong eruption from a volcanic island. The initial eruptions produced pumice fall deposits as well as pumice rafts. Then a relative quiescence with a series of small intermittent eruptions followed the onset. The duration of the quiescences were 90 days for Krakatau 1883 and 25 days for Hunga Tonga 2021-2022. Such periods might be a preparation time for the following climax eruption in their magma plumbing system. The destruction of edifices started in the late stage of the quiescence in Krakatau and the later strong eruption in Hunga Tonga. This also might be an important preparation process in terms of structural instability. The climax eruptions in both events continued for almost a day with the generation of multiple waves of tsunami. Moreover, large seismic unrest which might be related to the caldera collapse similarly followed the climax eruption and continued for one month. The future research effort into the subaerial as well as the submarine part of the Hunga Tonga volcano will provide essential insights into such rare but extremely dangerous escalating-type eruptions.