New research has highlighted just how powerful the Hunga Tonga-Hunga Ha'apai eruption on January 15 was. It was not just the most powerful in this century, it also released atmospheric waves with an energy that has not been seen in 139 years. It was the loudest sound on Earth since the Krakatoa eruption of May 20, 1883.
The work, published in two papers in the journal Science, suggests that an unexpected and anomalous atmospheric wave created by the eruption contributed to the tsunami. This might explain why the waves reached locations two hours earlier than the conventional model of tsunamis predicted. The sonic boom from the eruption was heard all the way in Alaska, 6,200 kilometers (3,850 miles) away.
“This atmospheric waves event was unprecedented in the modern geophysical record,” lead author Robin Matoza, an associate professor at UC Santa Barbara’s Department of Earth Science, said in a statement.
The waves produced by the eruption circled the planet in one direction four times and in the other three times. In particular, the team collected data on the so-called Lamb wave, a longitudinal pressure wave of such low frequency it requires the effect of gravity to be taken into account.
The team measured that the Lamb wave moving at over 1,100 kilometers (700 miles) per hour and reached an altitude of 450 kilometers (280 miles), well into the ionosphere. That is higher than the orbit of the International Space Station.
“The atmospheric waves were recorded globally across a wide frequency band,” said co-author David Fee at the University of Alaska Fairbanks Geophysical Institute. “And by studying this remarkable dataset we will better understand acoustic and atmospheric wave generation, propagation and recording.”
“This has implications for monitoring nuclear explosions, volcanoes, earthquakes and a variety of other phenomena,” Fee continued. “Our hope is that we will be better able to monitor volcanic eruptions and tsunamis by understanding the atmospheric waves from this eruption.”
The second study focused mostly on how the tsunami differed from expectations. Tsunamis from underwater volcanic eruptions are created by water displacement due to seafloor crustal deformation and atmospheric pressure waves.
But the Lamb wave appeared to play a significant role in this deadly tidal wave, making it arrive much earlier than expected. The researchers advise that future models take into account this particular scenario allowing better tsunami prediction and the ability to save lives.
The Hunga Tonga-Hunga Ha'apai tsunami injured 19 people and killed at least six across the Pacific. Several people remain missing.
