An underwater volcanic eruption in the South Pacific created the highest-ever recorded plume, reveals a new study.

The Hunga Tonga-Hunga Ha’apai volcanic blast reached 35.4 miles – becoming the first to break through the mesosphere, say scientists.

This is a layer of atmosphere 30 to 50 miles above Earth. The explosion on January 15 this year was one of the most powerful ever observed.

It triggered devastating tsunamis. Sound waves carried 6,200 miles – to Alaska. Thousands were left homeless.

Now scientists have precisely measured the towering column of ash and water that rose upwards – using images captured by satellites.

Lead author Dr Simon Proud, of the University of Oxford, said: ‘It is an extraordinary result as we have never seen a cloud of any type this tall before.

‘Furthermore, the ability to estimate the height in the way we did is only possible now that we have good satellite coverage. It wouldn’t have been possible a decade or so ago.’

The researchers used a technique known as ‘the parallax effect’ – the difference in an object’s position when viewed from multiple lines of sight.

You can see this for yourself by closing your right eye, and holding out one hand with the thumb raised upwards.

If you then switch eyes, so your left is closed and your right open, your thumb will appear to shift slightly against the background.

By measuring this apparent change in position and combining this with the distance between your eyes, you can calculate the distance to your thumb.

Results published in the journal Science showed the plume hit an altitude of 57 kilometres (35.4 miles) – smashing previous records.

The 1991 eruption of Mount Pinatubo in the Philippines reached 40 km (25 miles) and 1982’s El Chichon in Mexico 31 km (19 miles).

It is also the first evidence of a volcanic eruption ejecting material through the stratosphere and directly into the mesosphere.

The height of a plume can be estimated by measuring the temperature at the top by infrared-based satellites and comparing this to a reference vertical profile.

In the troposphere, the lowest layer of the atmosphere, temperature decreases with height.

But if the plume penetrates into the next layer, the stratosphere, this method becomes ambiguous.

Temperature begins to increase again with height – due to the ozone layer absorbing solar ultraviolet radiation.

The volcano in the Tongan archipelago is covered by three geostationary weather satellites – enabling the international team to apply the parallax effect to aerial images.

Crucially, during the eruption itself, the satellites recorded images every 10 minutes, documenting rapid changes in the plume’s trajectory.

The researchers now plan to construct an automated system to compute the heights of volcano plumes using the parallax method.

Co-author Dr Andrew Prata, also from Oxford, added: ‘We would also like to apply this technique to other eruptions and develop a dataset of plume heights that can be used by volcanologists and atmospheric scientists to model the dispersion of volcanic ash in the atmosphere.

‘Further science questions that we would like to understand are: Why did the Tonga plume go so high? What will be the climate impacts of this eruption? And what exactly was the plume composed of?’

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