The undersea volcano that erupted in January this year near Tonga sent unprecedentedly massive pressure waves through Earth’s atmosphere that circled the planet multiple times. It also generated infrasound that disturbed the ionosphere, seismic waves that triggered tsunamis, and powerful “thunderclaps” that were heard as far away as Alaska.
An international team of 67 scientists from 17 countries has recently published a new study in the journal Science in which they conclude that the January 15, 2022 eruption of the volcano Hungarian submarine, in Tonga, produced an explosion in the atmosphere of a size that has not been documented in the modern geophysical record. According to experts, the magnitude of the event can be compared to the eruption of the Krakatoa volcano in 1883, considered one of the most powerful and damaging seismic events in the history of the planet.
Atmospheric and sound waves around the planet
As described in the investigation, the event generated a wide range of atmospheric waves observed globally by various ground and space instrumentation networks. The most prominent is Lamb wave surface-guided, which was observed to propagate for four cycles, or passages around the Earth, over the course of six days.
A Lamb wave is an elastic wave that propagates in plate-like structures, deforming the thickness as they travel across the surface. Based on the amplitudes of the Lamb waves that were recorded, the researchers concluded that the hunga climate explosion it was comparable in size to that generated by the eruption of the Krakatoa volcano and other similar phenomena.
At the same time, the Hunga eruption produced a remarkable infrasound, that is, an acoustic wave or sound wave whose frequency is below the spectrum audible by the human ear. In this case, infrasound was detected globally, along with long-range audible sound and disturbances in the ionospherethe layer of the Earth’s atmosphere that extends approximately between 80 and 500 kilometers in altitude: in it important ionization processes take place and intense concentrations of free electrons are produced.
Strong impacts on different systems at the same time
In addition, seismometers around the world recorded pure and coupled air-ground seismic waves, which had an impact in both contexts. But the most important thing is the air-sea coupling of the seismic waves, since this double influence probably contributed to the rapid arrival of tsunamis in the area of the event, according to another study also published in Science. The researchers verified that the waves reached the region two hours earlier than expected in this type of event.
According to a press release from the University of Liverpool, in the United Kingdom, which was one of the academic centers that participated in this international scientific effort, the audible sounds generated by the earthquake, which consist of brief and repeated “booms”, were reported throughout Alaska, more than 10,000 kilometers from the eruption in Tonga.
Apparently, the reason for the huge impact of the eruption was because the hot, gas-laden magma came into contact with the seawater very quickly. The almost instantaneous transfer of intense heat between the hot magma and the cold water caused violent explosions, capable of tear apart the magma. In this way, a sudden interaction between the different elements would have led to the unusual violence of the phenomenon.
Atmospheric waves and global seismoacoustic observations of the January 2022 Hunga eruption, Tonga. Robin S. Matoza et al. Science (2022). DOI:https://doi.org/10.1126/science.abo7063
Global fast-traveling tsunamis driven by atmospheric Lamb waves on the 2022 Tonga eruption. Tatsuya Kubota et al. Science (2022). DOI: https://doi.org/10.1126/science.abo4364