Editor’s Note: This story was updated on January 19, 2022, to add more context and quotes from scientists studying the volcano.
A powerful volcanic eruption has obliterated a small, uninhabited South Pacific island known as Hunga Tonga-Hunga Ha‘apai. Damage assessments are still ongoing, but preliminary reports indicate that some communities in the island nation of Tonga have been severely damaged by volcanic ash and significant tsunami waves.
The volcano had sporadically erupted multiple times since 2009. The most recent activity began in late December 2021 as a series of Surtseyan eruptions built up and reshaped the island, while sending bursts of tephra and volcanic gases spewing from the vent. Relatively powerful blasts shook Hunga Tonga-Hunga Ha‘apai on January 13, but it was an even more intense series of explosions early on January 15 that generated atmospheric shock waves, sonic booms, and tsunami waves that traveled the world.
Several Earth-observing satellites collected data during and after the eruption. Scientists affiliated with NASA’s Disasters program are now gathering imagery and data, and they are sharing it with colleagues around the world, including disaster response agencies.
The sheer power of the eruption was quickly apparent in satellite imagery. As shown in the animation above, a vast plume of material created what volcanologists call an umbrella cloud with crescent-shaped bow shock waves and a vast number of lightning strikes.
“The umbrella cloud was about 500 kilometers (300 miles) in diameter at its maximum extent,” said Michigan Tech volcanologist Simon Carn. “That is comparable to Pinatubo and one of the largest of the satellite era. However, the involvement of water in the Tonga eruption may have increased the explosivity compared to a purely magmatic eruption like Pinatubo.”NOAA's Geostationary Operational Environmental Satellite 17 (GOES-17) captured the images for the animation above. The natural-color views from the satellite’s Advanced Baseline Imager were acquired between 5 and 8 p.m. local time (04:00 to 07:00 Universal Time) as the volcanic plume expanded upward and outward over the South Pacific. (NASA builds and launches the GOES series of satellites for NOAA.)
The second image, based on data collected on January 16 by the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) mission, shows material from the eruption rising to an altitude of 31 kilometers (19 miles). Other CALIPSO data collected on January 15 indicates that a small amount of ash and gas may have reached as high as 39.7 kilometers (24.7 miles).
“This is by far the highest volcanic plume we've ever measured with CALIPSO,” said Jason Tackett, a researcher at NASA’s Langley Research Center. CALIPSO was launched in 2006 by NASA and France’s National Centre for Space Studies (CNES).
The eruption was powerful enough to inject volcanic material into the stratosphere, which generally begins above 15 kilometers (9 miles) in this part of the world. Scientists watch closely when volcanic materials reach this relatively dry layer of the atmosphere because particles linger much longer and travel much farther than if they remain in the lower, wetter troposphere. If enough volcanic material reaches the stratosphere, it can start to exert a cooling influence on global temperatures.
Despite the extreme height of the January 15 plume, scientists do not expect it to have much impact on climate. Satellite observations indicate the eruption injected about 0.4 teragrams of sulfur dioxide into the upper atmosphere, but the threshold for climate impacts is about 5 teragrams. “It is not unlike a dozen other eruptions that have occurred in the past 20 years in terms of likely impacts on climate,” explained Brian Toon, an atmospheric scientist at the University of Colorado. “It is possible the impacts will be observable in very closely studied data (when the effects of La Niña and El Niño are removed), but the impacts will be too small to be felt by the average person.”
Why this eruption was so violent is not clear yet. “With something this explosive, it is typically a consequence of a large volume of seawater coming into contact with a large reservoir of magma in a confined geologic setting,” explained Daniel Slayback, a NASA scientist who visited Hunga Tonga-Hunga Ha‘apai in 2019 to study how erosion was affecting the youngest parts of the island. Understanding erosion processes around volcanic features on Earth provides insights into how related processes may have played out in other parts of the solar system, including Mars.
Preliminary imagery from commercial satellites and European and Canadian radar imagers suggest that little of Hunga Tonga-Hunga Ha‘apai still stands above the water line. The volcanic island first rose from the sea in January 2015. Eruptive activity built up ash around a new volcanic cone and connected the older, more lava-based islands of Hunga Tonga and Hunga Ha‘apai to create Hunga Tonga-Hunga Ha‘apai.
Signs of the island’s recent demise were easy for satellites to spot in the seas. The trio of natural-color images above shows how sediment, ash, pumice, and possibly continuing emissions from the volcano discolored the water in the days after the event. The images were acquired by the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Aqua satellite.
The geologic record suggests Hunga Tonga may have produced large explosive eruptions like this in the past. “I just didn't expect to see one happen quite so soon,” said Slayback. “It was a beautiful little island with a thriving ecosystem of grasses, tropical birds, and other wildlife.”
NASA Earth Observatory images by Joshua Stevens and Lauren Dauphin, using CALIPSO data from NASA/CNES, MODIS and VIIRS data from NASA EOSDIS LANCE and GIBS/Worldview and the Suomi National Polar-orbiting Partnership, and GOES imagery courtesy of NOAA and the National Environmental Satellite, Data, and Information Service (NESDIS). Story by Adam Voiland, with Mike Carlowicz.