At 17:14 local time on 15 January 2022, a submarine volcano 65 km north of Tonga's main island produced the largest atmospheric explosion recorded by modern instrumentation. NASA called it "hundreds of times more powerful than Little Boy." The blast yield is estimated at 61–200 megatons — larger than the Tsar Bomba, the largest nuclear weapon ever detonated.
The eruption was heard 9,300 km away in Anchorage, Alaska, where low-frequency booms persisted for 30 minutes. It was heard in Yukon, 9,700 km away. The sound reached New Zealand two hours later. The atmospheric pressure wave circled the Earth at least four times, recorded by 50 barographs worldwide. Pressure fluctuations of 2.5 hPa were measured in Switzerland.
Described as a "magma hammer," the volcano produced four underwater thrusts, displacing 10 cubic kilometres of rock, ash, and sediment. Only the 1883 Krakatoa eruption rivalled the atmospheric disturbance.
Volcanic tsunamis rarely travel far from the source. This one crossed ocean basins because the atmospheric shockwave — the Lamb wave — coupled to the ocean, generating a meteotsunami that earthquake-based warning systems didn't account for. Waves arrived earlier than forecast. The tsunami was even detected under 410 metres of ice at the Ross Ice Shelf in Antarctica.
Tonga's only fibre-optic cable was cut — not just broken, but torn into multiple pieces. A 55 km section was lost entirely, sections were moved 5 km from their original position, and everything was buried under 30 cm of silt. The cause: a turbidity current — an underwater avalanche of ash and sediment. Same phenomenon that broke 12 transatlantic cables in the 1929 Grand Banks earthquake. Total replacement: 87 km of cable. Tonga was offline for over a month.
Satellite surveillance flights by New Zealand and Australian defence forces provided the first images of the damage. No news from Tonga for days.
The eruption injected 146 million tonnes of water vapour into the stratosphere — 10% of its normal total content. This water is expected to remain for 5–10 years. It disrupted the stratospheric temperature balance, created anomalous winds, and may have contributed to the record Antarctic ozone hole of September 2023 (26 million km²).
Unlike Pinatubo (1991), which cooled the planet via sulfur aerosols, Hunga Tonga's water vapour acted as a greenhouse gas, overriding the aerosol cooling and producing a net warming effect. One study estimated a 7% increase in the probability of exceeding 1.5°C warming in at least one of the next five years. People in the Southern Hemisphere saw purple sunsets for months.
Mango Island: all structures destroyed. Fonoifua: two buildings left standing. Nomuka Iki: stripped bare by 20-metre waves. A new caldera formed — 4 km wide, 850 m deep. The seafloor was blanketed with ash for months, decimating deep-sea hot spring communities even at 2.4 km depth (Beinart, Nature Communications, 2024).