It is reported that these are the many observations by the 76 scientists from 17 countries make up the team reported, they studied the eruption of the atmospheric wave, which is since 1883 Krakatau eruption largest known volcanic eruptions. It is reported that the team’s work compiled from within the abnormally short time, and published in the “Science” on May 12, 2022.
David Fee, director of the Wilson Alaska Technology Center at the University of Alaska’s Fairbanks Institute of Geophysics, is lead author of the research paper and one of four scientists at the center who participated in the study.
The eruption of the Hunga volcano near the island of Tonga has provided unprecedented insight into the behavior of some atmospheric waves. Alaska’s dense network of barometers, infrasound sensors, and seismometers contributed to the data.
“Our hope is that by understanding the atmospheric waves from this eruption, we will be able to better monitor volcanic eruptions and tsunamis,” said Fee, who is also a coordinating scientist for the Institute of Geophysics’ section at the Alaska Volcano Observatory.
“Atmospheric waves are recorded globally over a wide frequency band, and by studying this extraordinary data set we will better understand the generation, propagation and recording of sound and atmospheric waves. This is useful for monitoring nuclear explosions, volcanoes, earthquakes and various other phenomena,” he continued.
The researchers found the behavior of erupting Lamb waves, a type named after its 1917 discoverer, British mathematician Horace Lamb, to be particularly interesting.
The largest atmospheric explosions, like those from volcanic eruptions and nuclear tests, produce Lamb waves. They can last from minutes to hours. Lamb waves are a type of guided waves, those waves that travel parallel to the surface of a material and extend upwards. As Hunga erupted, the waves traveled along the Earth’s surface and circled the planet four times in one direction and three in the opposite direction — the same thing observed in the 1883 eruption of Krakatau .
“Lamb waves are rare. We have very few high-quality observations of them. By understanding Lamb waves, we can better understand the source and the eruption. It is associated with the production of tsunamis and volcanic plumes, and possibly eruptions. The higher frequency infrasound waves are related to sound waves,” Fee said.
Lamb waves consist of at least two pulses near Hunga, the first with a 7 to 10 minute pressure increase, followed by a second, larger compression and a subsequent prolonged pressure drop. The wave also reached Earth’s ionosphere before rising to an altitude of about 280 miles at 700mph, according to ground station data.
A major difference between the Lamb wave of the Henga explosion compared to the Lamb wave of 1883, the paper says, is the sheer volume of data collected due to more than a century of technological advancement and the proliferation of sensors around the globe.
Scientists noted other findings of atmospheric waves linked to volcanic eruptions, including “significant” long-range infrasound waves — sounds too low in frequency for humans to hear. Infrasound waves arrived after Lamb waves and were audible in some areas.
The paper notes that the audible sound traveled about 6,200 miles to Alaska, where they heard repeated roars around the state about nine hours after the eruption.
“I heard these sounds, but definitely didn’t think it was a volcanic eruption from the South Pacific at the time,” Fee said.
The Alaska report is the furthest documented description of the sound from the source. This is partly due to global population growth and advances in social connectivity, the paper notes.
Fee said they will study these signals for years to understand how atmospheric waves are created and how they travel so well on Earth.