Hunga Tonga–Hunga Ha'apai
The submarine Tongan volcano whose January 2022 eruption sent the highest plume ever recorded into the mesosphere
For most of recorded history Hunga Tonga–Hunga Ha'apai was little more than two uninhabited islets about 65 kilometers north of Nukuʻalofa, the capital of Tonga, the visible tips of a large submarine volcano. On January 15, 2022, it produced the largest explosion in the atmosphere ever recorded by modern instruments. Its plume reached about 57 kilometers, into the mesosphere and the highest on record, and the blast sent a pressure wave around the planet several times, registered by barometers worldwide. Tsunamis struck Tonga and crossed the Pacific, and the eruption injected so much water vapor into the stratosphere that scientists expect its effects on the upper atmosphere to linger for years.
The volcano lies on the Tonga–Kermadec arc, where the Pacific Plate dives beneath the Indo-Australian Plate along the Tonga Trench. Before 2022 its two islets, Hunga Tonga and Hunga Haʻapai, rose to about 114 meters, and eruptions in 2014 and 2015 had joined them with a new cone of ash. The 2022 explosions destroyed most of that new land and left only small remnants of the old islets above water. Surveys found the floor of the caldera about 850 meters below sea level and an estimated 6 to 7 cubic kilometers of material spread across the seafloor, much of it carried by fast underwater density currents that cut Tonga's only international telecommunications cable. The eruption also produced about 200,000 lightning flashes in a single hour, the most intense lightning activity ever recorded.
Explosive activity began in December 2021 and peaked on January 15, 2022. Waves of up to about 15 to 20 meters swept parts of Tonga, destroying homes on Tongatapu, ʻEua and the Haʻapai islands, and ash blanketed the kingdom. Tonga reported four deaths, and two people drowned in Peru when the tsunami reached South America, while the cable break left the country largely cut off for weeks. The World Bank estimated damage at about US$182 million, around 36 percent of Tonga's GDP. Scientists rate the eruption between VEI 5 and 6. It put about 150 million tonnes of water vapor into the stratosphere, raising its water content by roughly 10 percent, while releasing relatively little sulfur dioxide. Tonga Geological Services found no visible signs of activity or unrest during an overflight in February 2026.