The Tonga explosion that rocked the Pacific Ocean sent shockwaves across the planet and was more than a spectacular eruption. It triggered a tsunami that swept inland and into Japan and the western coasts of the Americas. It turned Tonga’s main island into a grey moonscape and cut off communications by severing a single underwater fiber-optic cable. It also sent an atmospheric shock wave that ripped through Earth’s upper atmosphere, creating hurricane-like winds and “unusual electric currents” in the ionosphere.
Scientists have been analyzing all sorts of data to determine what happened, including seismic records, radar images, and satellite observations. But it’s only now that they are beginning to understand the full impact of the Hunga Ha’apai (HTHH) eruption, which was unprecedented in scale.
They’ve found that only about 30 percent of the existing magma came out in the January 15 blast, which displaced vast amounts of water and sprayed finely-grained ash across an area that is nearly a million square miles. The rest of it still resides inside the submarine volcano, and the scientists believe plenty more can still erupt.
They also believe that the massive explosion was not simply a result of the sudden release of pressure built up by the collapsing caldera floor. Close to the volcano, factors like earthquakes and the turbulent sloshing of the sea stirred up by volcanic pyroclastic flows produced waves that rose as much as 50 feet. But the tsunami was also fueled by rapid air pressure changes that occurred far from the explosion site. The shockwaves generated by the explosion caused air pressure to spike on one side of the globe and drop on the other, pumping energy into the tsunami.
While the Hunga Ha’apai eruption reminds us how dangerous it can be to live near active submarine volcanoes, researchers also say we must learn much more about these dangerous beasts. The eruption revealed how fast and intense subduction can be where two tectonic plates meet and how a volcano can rise out of a region of thin crust that is very quickly being melted.
While more volcanic activity is unlikely to happen at Hunga Ha’apai shortly, scientists are working to improve volcanic monitoring at Tonga and elsewhere worldwide. By deploying onshore and offshore seismic sensors and infrasound systems, they hope to anticipate such dangerous events better. They also identify other volcanoes that pose potential threats, including ones in South America, Africa, and Asia. By the end of 2022, work should be underway on an uncrewed surface vessel — called Maxlimer — that will be used to map the magma plumbing system under the Tonga volcano and others. It could help prevent future disasters, but it will require significant funding. NIWA has been putting the money in, and other donors have pledged support.
