Tonga underwater volcanic eruption blasted 58,000 Olympic swimming pools-worth of water into the stratosphere and could weaken the ozone layer, scientists warn

  • Tonga volcanic eruption in January blasted 146 million tonnes of water vapour
  • NASA scientists think the volume could cause a temporary warming event
  • The water could also boost chemical reactions that deplete the ozone layer

Tonga’s volcanic eruption in January blasted enough water to fill more than 58,000 Olympic-size swimming pools – and could weaken the ozone layer.

Scientists who examined the amount of water vapour ejected by the Hunga Tonga-Hunga Ha’apai volcano described it as ‘unprecedented’.

The powerful steam was formed when seawater in the South Pacific came into contact with the lava and was ‘superheated’. 

The eruption created sound waves heard as far as Alaska 6,200 miles away, in a sonic boom that circled the globe twice. 

In a new study, experts from NASA’s Jet Propulsion Laboratory predict the volume of water could be enough to temporarily affect the global average temperature.

It could also temporarily boost chemical reactions in the atmosphere that worsen the depletion of the ozone layer. 

‘We’ve never seen anything like it,’ said atmospheric scientist Dr Luis Millán.

In a new study, experts from NASA’s Jet Propulsion Laboratory predict the volume of water expelled during the eruption could be enough to affect the global average temperature 

Just before nightfall reached Tonga, the eruption (lower left) created sound waves heard as far as Alaska 6,200 miles away, in a sonic boom that circled the globe twice

Hunga Tonga-Hunga Ha’apai, an underwater volcano in the South Pacific, spewed ash and other debris as high as 25 miles into the atmosphere when it erupted in January 

In the study, published in Geophysical Research Letters, Dr Millán and his colleagues estimate that the Tonga eruption sent around 146 million tonnes of water vapour into the stratosphere.

The stratosphere is the layer of the atmosphere between about 8 and 33 miles (12 and 53 kilometres) above the Earth’s surface.

Water from the January 15 eruption equates to approximately 10 per cent of the water content already present in the stratosphere.

Comparable amounts of water have only been blasted to such high altitudes by volcanoes twice before in the 18 years that NASA has been taking measurements.  

These were the 2008 Kasatochi event in Alaska and the 2015 Calbuco eruption in Chile.

The water from these events dissipated quickly, but NASA researchers claim the liquid from the Tonga volcano could remain in the stratosphere for up to ten years.

A: The water vapour entered the stratosphere primarily in the tropics, where rising dry and moist air is recorded in annual cycles. The vapour from the eruption has disrupted this ‘heartbeat’ signal. B: Time series of near-global water vapour at atmospheric pressures of 100 and 31 hPa using data from MLS and GOZCARDS

The Hunga Tonga-Hunga Ha’apai eruption caused many effects, like atmospheric waves, extreme winds and unusual electric currents, that were felt around the world and into space

To determine the volume of water vapour, scientists analysed data from Microwave Limb Sounder (MLS) instrument on NASA’s Aura satellite.

This measures atmospheric gases, including water vapour and ozone, by observing natural microwave signals emitted from Earth’s atmosphere.

The researchers noticed readings increased dramatically after the Tonga volcano erupted.

Dr Millán, who manages the instrument from Pasadena, California, USA, said: ‘We had to carefully inspect all the measurements in the plume to make sure they were trustworthy.

‘MLS was the only instrument with dense enough coverage to capture the water vapor plume as it happened, and the only one that wasn’t affected by the ash that the volcano released.’

Ash sent spewing into the air from the massive underwater volcanic eruption in Tonga was photographed by International Space Station astronauts.

NASA shared the remarkable pictures taken out of the ISS Cupola windows, showing a blanket of ash from plumes spewing thousands of feet into the atmosphere. 

The event was so striking that satellites captured the moment of the eruption, with astronauts on the ISS taking images of plumes and blankets of ash over the region.  

Read more: Ash from the volcanic eruption in Tonga is seen from SPACE 

When the water molecules break down in the stratosphere, they release reactive hydrogen oxide molecules.

These react with and destroy ozone by themselves, but also convert chlorine-containing gases into other destructive molecules.

Water vapour also traps heat, so the eruption could result in a temporary warming effect on the surface of Earth, for what the researchers think may be the first time.

While it is counted as a ‘greenhouse gas’, like carbon dioxide and methane, any warming would not be enough to exacerbate climate change effects.

This is because the warmth would dissipate as the extra water was naturally cycled out of the stratosphere. 

Conversely, previous massive volcanic eruptions, like Krakatoa, blasted ash, dust and gases into the atmosphere that reflect sunlight back into space, and produced a cooling effect.

In the paper, Dr Millán wrote: ‘It is critical to continue monitoring volcanic gases from this eruption and future ones to better quantify their varying roles in climate.’ 

The researchers believe that the Tonga volcano was only able to produce the vast amounts of water vapour it did because of its precise depth underwater. 

Its caldera – the large crater formed while magma begins erupting – is thought to be located about 490 feet (150 metres) down.

If it were any shallower, there wouldn’t have been enough seawater superheated by the magma to account for the volume of stratospheric water vapour.

However, any deeper and the pressure from the ocean could have muted the violent eruption.

Radar surveys before and after the eruption show that only small parts remain of two uninhabited Tongan islands above the volcano – Hunga Tonga and Hunga Ha’apai 


Hunga Tonga-Hunga Ha’apai, an underwater volcano in the South Pacific, spewed debris as high as 25 miles into the atmosphere when it erupted on January 15.

It triggered a 7.4 magnitude earthquake, sending tsunami waves crashing into the island, leaving it covered in ash and cut off from outside help. 

It also released somewhere between 5 to 30 megatons (5 million to 30 million tonnes) of TNT equivalent, according to NASA Earth Observatory.  

Digital elevation maps from the NASA Earth Observatory also show the dramatic changes at Hunga Tonga-Hunga Ha’apai, the uppermost part of a large underwater volcano. 

Prior to the explosion earlier this month, the twin uninhabited islands Hunga Tonga and Hunga Ha’apai were merged by a volcanic cone to form one landmass.

Hunga Tonga and Hunga Ha’apai are themselves remnants of the northern and western rim of the volcano’s caldera – the hollow that forms shortly after the emptying of a magma chamber. 

NASA said the eruption ‘obliterated’ the volcanic island about 41 miles (65km) north of the Tongan capital Nuku’alofa, on the island of Tongatapu (Tonga’s main island).

It blanketed the island kingdom of about 100,000 in a layer of toxic ash, poisoning drinking water, destroying crops and completely wiping out at least two villages.

It also claimed at least three lives in Tonga and resulted in the drowning deaths of two beachgoers in Peru after freak waves hit the South American country.  

Peruvian authorities have declared an environmental disaster after the waves hit an oil tanker offloading near Lima, creating a huge slick along the coast.


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