An underwater volcano erupted in January near the Pacific nation of Tonga and sent massive waves of pressure through Earth’s atmosphere, where they smashed into the planet multiple times. A new study shows that the last volcano to produce such large ripples in the atmosphere was Krakatau in 1883, during one of the most destructive volcanic eruptions in recorded history.
“This atmospheric wave event is unprecedented in the modern geophysical record,” said first author Robin Matoza, an associate professor in the Department of Earth Sciences at the University of California, Santa Barbara. The study, published Thursday (May 12) in the journal Sciencerevealed that the pressure pulse was generated by Tonga volcano is “comparable in amplitude to that of the Krakatau eruption of 1883 and to an order of magnitude greater than that of 1980. Mount St. Helens Matoza told Live Science in an email. The higher the amplitude of the wave, the stronger it is.
A second study, also published May 12 in Science, suggested that this powerful pulse not only shook the atmosphere, but also created ripples that ran across the ocean below. In fact, the atmospheric waves that have produced small, fast-moving meteors – that is, a series of waves caused by air pressure disturbances – reach the shore several hours before the usual tsunamis, because earthquakes caused by volcanic eruptions.
What’s surprising is Tatsuya Kubota, a researcher at the National Institute of Earth Sciences and Disaster Resilience at the National Research Institute for Earth Sciences and Disaster Resilience. in Japan and the first author of the second study. Kubota told Live Science in an email: “The height of the tsunami ‘precursor’ … is approximately a few centimeters, although it depends on the location.”
Related: Impressive photos show the terrible aftermath of Tonga’s massive eruption and tsunami
An eruption of extreme energy
The Tonga volcano – known as Hunga Tonga-Hunga Ha’apai, or just Hunga – is located about 65 kilometers northwest of the Tongan capital Nuku’alofa. It is one of 12 known underwater volcanoes in the Tonga-Kermadec volcanic arc, a geological structure that runs along the western edge of the Pacific Plate of the The earthof the crust, according to the Smithsonian’s Global Volcano Program.
When Hunga erupted in mid-January, the plume of gas and the resulting particles collided with the mesosphere – the third layer of Earth’s atmosphere – making it a largest volcanic cluster in satellite records. The the amount of energy released in the eruption comparable to what could be produced by 4 to 18 megatons of TNT exploding, or more than 100 Hiroshima-scale bombs exploding at once.
After the record-breaking eruption, Matoza and a team of more than 70 scientists from 17 countries set out to record what atmospheric waves were produced by the explosion. To do so, they pulled data from a variety of ground- and space-based monitoring systems that recorded the eruption as it unfolded.
The team found that, of all the atmospheric waves produced by the explosion, the so-called Lamb waves were the most prominent. Sheep waves run along the surface of the Earth and are similar to sound waves in that they create vibrations in the medium they pass through. However, Lamb waves propagate at extremely low frequencies, “where the influence of Gravitation Matoza said.
Researchers rarely record Lamb waves, because they arise only from extremely large explosions in the atmosphere, on the scale of large volcanic eruptions and nuclear tests. “They are not usually observed for smaller volcanic eruptions,” Matoza told Live Science.
Related: 4-foot tsunami hits Tonga after underwater volcano erupts
At their highest, the Lamb waves produced by the Hunga eruption had an amplitude of 280 miles (450 km), which means they hit ionosphere – a dense layer of charged particles located about 35 to 620 miles (60 to 1,000 km) above the planet’s surface. Within six days, these waves radiated outward from the volcanic region, orbiting the Earth four times in one direction and three times in the other. Based on historical data, the 1883 eruption of Krakatau produced Lamb waves that orbited the Earth the same number of times, the researchers say.
The team’s Lamb wave observations are consistent with previous models of the Hunga eruption event proposed by Nedjeljka Žagar, professor of theoretical meteorology at the University of Hamburg, and her colleagues. “We were able to simulate the Hunga Tonga Lamb wave just two days after this event,” Žagar told Live Science in an email.
In their own Science study, Kubota and his colleagues connected the dots between these Lamb waves and the fastest tsunamis observed after the eruption. They found that the timing of the Lamb wave and the “precursor” of the tsunami appeared to coincide. It is remarkable that these foretelling waves made landfall two hours earlier than expected for a normal tsunami, largely due to the sudden deformation of the seafloor.
In addition to the giant Lamb wave and the fast-moving tsunami, the eruption in Hunga also produced long-range sound waves and infrasound – meaning sound waves too low in frequency for humans to hear, Matoza and the others. said his colleague. The prominent Lamb waves lead the herd, followed by the infrasound waves and then the audible waves. Notably, audible sounds, including short, repetitive “bangs”, have been reported across Alaska, more than 6,200 miles (10,000 km) from the Hunga eruption.
Originally published on Live Science.
https://www.livescience.com/atmospheric-pressure-waves-from-hunga-volcano Record-shattering Tonga volcanic eruption sent atmospheric waves zipping around the Earth