Tonga volcano was the most ferocious eruption in 140 years

(CNN)The volcanic eruption on an island near Tonga in January was as powerful as the 1883 Krakatoa eruption in Indonesia, one of the deadliest and most destructive volcanic events on record.

Scientists have begun to piece together what happened during the January 15 eruption of the undersea Hunga Tonga-Hunga Ha'apai volcano about 65 kilometers (40 miles) north of Tonga's capital that killed at least three people. The eruption has defied easy explanation and upended scientists' understanding of this type of volcano.
The volcanic eruption sent rarely observed pressure waves around the globe for six days and unleashed an unexpected type of tsunami wave, according to two new studies published on Thursday in the journal Science. The huge plume of gases, water vapor and dust also created hurricane-strength winds in space, NASA said in a separate study published this week.
    Early data in the aftermath of the explosion suggested it was the biggest since the 1991 Mount Pinatubo eruption in the Philippines, but the Science studies, which involved 76 scientists in 17 countries, have suggested that the pressure waves it unleashed were similar to those generated by the cataclysmic 1883 Krakatoa eruption and 10 times larger than those from the 1980 Mount St. Helens eruption in Skamania County, Washington.

      'Unusually energetic'

      The Tonga eruption was "unusually energetic," the Science study researchers wrote. The low-frequency atmospheric pressure waves, called Lamb waves, detected after the eruption circled the planet in one direction four times and in the opposite direction three times, they revealed.
      A relatively rare phenomenon, these waves travel at the speed of sound. They aren't detectable by humans and are slower than shock waves, as they have been mistakenly described sometimes, said study author Quentin Brissaud, a geophysicist at the Norwegian Seismic Array in Oslo. Lamb waves were also observed during the Cold War after atmospheric nuclear tests.
        "It's quite rare. So Lamb waves are really related to large air volume displacements. And they mostly propagate along the Earth's surface," said coauthor Jelle Assink, senior geophysicist at the seismology and acoustics department at the Royal Netherlands Meteorological Institute.
        Moving across the surface of multiple oceans and seas, Lamb pressure waves from the explosion created a fast-moving spate of scattered tsunamis.
        Traditional tsunamis are usually linked with sudden changes in the ocean floor such as during an earthquake. Crucially, these so-called meteotsunamis travel much faster than traditional tsunamis, arriving two hours earlier than expected, and last longer, which could have implications for early warning systems.
        And because an atmospheric pressure wave generated them, the tidal waves appeared to "jump continents," with tsunamis recorded from the Pacific to the Atlantic, said coauthor Silvio De Angelis, professor of volcano geophysics in the department of Earth, ocean and ecological sciences at the University of Liverpool in the United Kingdom.