by An undersea volcano erupted in January near the Pacific nation of Tonga and sent massive pressure waves through Earth’s atmosphere, where they lapped the planet multiple times. The last volcano to generate such large ripples in the atmosphere was Krakatoa in 1883, during one of the most destructive volcanic eruptions in recorded history, a new study shows.
“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 research, published Thursday (May 12) in the journal Sciencerevealed that the pressure pulse generated by the Tonga volcano was “comparable in amplitude to that of the 1883 Krakatau eruption and by an order of magnitude greater than that of 1980 Mount Saint Helena eruption,” Matoza told WordsSideKick.com in an email. The larger the amplitude of a wave, the more powerful it is.
A second study, also published May 12 in Science, suggested that this powerful pulse not only shook the atmosphere, but also sent ripples through the ocean. In fact, the atmospheric waves generated small fast-traveling meteotsunamis, that is, a series of waves driven by alterations in air pressure, which reached the coast hours before the conventional seismically driven tsunamis generated by the explosion of the volcano. .
These small “precursor” tsunamis were observed around the world, mainly in the Pacific Ocean, but also in the Atlantic Ocean and the Mediterranean Sea, surprisingly, said Tatsuya Kubota, a researcher at the National Research Institute for Earth Sciences and Earth Resilience. Disasters in Japan and first author of the second study. “The height of the ‘precursor’ tsunamis…was approximately a few centimeters, although it depends on the location,” Kubota told LiveScience in an email.
Related: Dramatic Photos Show Horrific Aftermath Of Tonga’s Massive Eruption And Tsunami
An extremely energetic eruption
The Tonga volcano, called Hunga Tonga-Hunga Ha’apai, or simply Hunga, is located about 40 miles (65 kilometers) northwest of Tonga’s capital, Nuku’alofa. It is one of 12 known submarine volcanoes in the Tonga-Kermadec volcanic arc, a geological structure that runs along the western edge of the Pacific plate of the landthe bark, according to the Smithsonian Global Volcanism Program.
When Hunga erupted in mid-January, the resulting plume of gas and particles hit the mesosphere, the third layer of atmosphere above Earth’s surface, turning it into the largest volcanic plume in the satellite record. The amount of energy released in the eruption it was comparable to what could be generated by the explosion of 4 to 18 megatons of TNT, or more than 100 Hiroshima-scale bombs detonating at once.
After the record-breaking eruption, Matoza and a team of more than 70 scientists from 17 countries set out to document what atmospheric waves the explosion generated. To do so, they pulled data from numerous ground-based and space-based monitoring systems that had recorded the eruption as it unfolded.
The team found that, of all the atmospheric waves produced by the explosion, so-called Lamb waves stood out as the most prominent. Lamb waves travel along the Earth’s surface and are similar to sound waves in that they cause vibrations in the medium through which they travel. However, Lamb waves propagate at extremely low frequencies, “where the effects of gravity become meaningful,” Matoza said.
Researchers rarely record Lamb waves, because they only arise from huge explosions in the atmosphere, on the scale of major volcanic eruptions and nuclear tests. “They are not usually seen in smaller volcanic eruptions,” Matoza told Live Science.
Related: 4ft tsunami hits Tonga after explosive eruption of underwater volcano
At their highest point, the Lamb waves generated by the Hunga eruption had an amplitude of 450 km (280 miles), meaning they hit the ionosphere — a dense layer of electrically charged particles found between 35 and 620 miles (60 to 1,000 km) above the planet’s surface. Over the course of six days, these waves radiated outward from the volcano site, circling the Earth four times in one direction and three times in the other. Based on historical data, the 1883 Krakatau eruption generated Lamb waves that circled the Earth the same number of times, the researchers reported.
The team’s Lamb wave observations align with earlier models of the Hunga eruption event that were produced by Nedjeljka Žagar, a 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 the event,” and now the new Science study has provided more detail on how these waves propagated, using various geophysical measurements, Žagar told WordsSideKick.com in an email. .
In their own Science study, Kubota and colleagues connected the dots between these Lamb waves and the fastest tsunamis observed after the eruption. They found that the timing of Lamb waves and “precursor” tsunamis seemed to coincide. What is surprising is that these precursor waves made landfall more than two hours earlier than would be expected from conventional tsunamis, which are largely driven by sudden deformations in the seafloor.
In addition to Lamb’s huge waves and fast-moving tsunamis, Hunga’s eruption also produced incredibly long-range sound waves and infrasound, meaning acoustic waves too low in frequency to be heard by humans, Matoza and his colleagues reported. colleagues. Prominent Lamb waves led the pack, followed by infrasound waves and then audible sound waves. Remarkably, audible sounds, consisting of brief, repeated “booms,” were reported throughout Alaska, more than 6,200 miles (10,000 km) from Hunga’s eruption.
Originally published on Live Science.
