The Extraordinary and Disastrous Eruption of the Hunga Tonga-Hunga Ha’apai Volcano

On January 15, 2022, the largest volcanic eruption in decades devastated the island nation of Tonga in the South Pacific Ocean. The blast released a massive amount of energy, equivalent to between 4 and 18 megatons of TNT, which is hundreds of times more powerful than the nuclear bomb dropped on Hiroshima.

The explosion created a low-frequency pressure wave that circled the Earth, causing the entire atmosphere to oscillate. Ash has coated the islands, causing a serious shortage of clean drinking water, and a tsunami caused by the eruption wrought widespread damage. The effect on local agriculture is of particular concern, with ash covering crops, saltwater flooding the area, and acid rain a potential threat. The disaster also broke the nation’s only undersea cable, disconnecting most residents from contact with the outside world.

The volcano has been very active in recent years. In fact, the island on which it sat did not exist until 2015, when the volcano ejected enough material to connect the islands of Hunga Tonga and Hunga Ha’apai into one larger landmass. The volcano is huge, with a width of 12 miles and a height of 1.1 miles from the bottom of the sea floor. The newly created island represents just one section of its 3-mile-wide caldera — the bowl-shaped hollow formed at the center of a volcano by eruption-triggered collapse — sticking out of the water. However, the volcano’s recent eruption completely obliterated this new landform, tearing the two islands apart again and leaving shrunken versions of their former shapes in the wake of its destruction. 

In the weeks leading up to the massive January 15th eruption, there were several smaller Surtseyan eruptions, meaning they involve the violently explosive interaction between cold water and incredibly hot rising magma. However, most Surtseyan eruptions, such as those witnessed in the early weeks of 2022, involve only small amounts of water and magma coming into contact, and could not have caused the scale of eruption seen on January 15th.

NASA scientist Jim Garvin has hypothesized that some weakness in the rock structure of the volcano must have enabled a significant enough collapse for a massive amount of water to come into contact with the magma all at once, causing the huge explosion. Dr. Garvin’s team has been studying this volcano for years. They have been able to map the rapidly changing landscape in great detail using a combination of observations from a commercial satellite company, the Canadian Space Agency’s RADARSAT Constellation Mission, NASA’s ICESat-2 mission, and the Schmidt Ocean Institute. RADARSAT and ICESat-2 are both used to make altitude measurements, an area of study called altimetry; RADARSAT uses radio waves to do this, while ICESat-2 uses lasers. The Schmidt Ocean Institute uses sonar—underwater measurements utilizing sound waves—to produce bathymetry data. Bathymetry is the underwater version of altimetry; it refers specifically to the measurement of depth in a body of water.

Garvin’s team believes that the same island-forming volcanic processes that shaped the landscape of Hunga Tonga-Hunga Ha’apai may have taken place on a water-covered Mars 2-3 billion years ago. Studying these processes on Earth can thus help Garvin’s team make conclusions about the formation of similar landforms observed on Mars.

This article was edited by Sarah McNamara and Anagha Aneesh.