The Tonga volcano produced a plume 68 times taller than the Burj Khalifa

When a volcano erupts, it ejects large amounts of smoke containing ash, gases, water, and other particles. This smoke or volcanic plume bursts out of the volcano with such enormous pressure that it reaches a height of several kilometers into the Earth’s atmosphere. Can you imagine how high the smoke from a volcano could go?

A team of researchers from the University of Oxford and Rutherford Appleton Laboratory (RAL) has recently found that the plume from the Hunga-Tonga-Hunga-Ha'apai volcano erupted this year in January went up to 57 km (35.41 miles) in height. No amount of plume from any volcano on Earth has ever reached such heights.

This is incredible because “for most explosive volcanic eruptions, the height limit is reached when the plume hits the tropopause (end of troposphere layer i.e. 10.5 mlies/17km above the equator),” one of the authors and postdoctoral research assistant at Oxford, Dr. Andrew Prata told IE.

These findings suggest that the smoke from the volcano not just went through the troposphere but even crossed the stratosphere (10.5-31 miles/17-50 km) and landed somewhere in the mesosphere (31-60 miles/50-90 km) layer of our atmosphere.

How did the scientists measure the height of the highest volcanic plume?

The smoke from a volcanic explosion changes the temperature of the troposphere. In the case of an ordinary volcano plume, where the smoke from the volcano only remains within the boundary of the troposphere, scientists employ one or two infrared-based satellites to measure the change.

The satellites estimate the height of the plume by comparing the temperature change recorded at the maximum height with a reference vertical temperature profile (different layers of the atmosphere have different temperatures) of the atmosphere.

However, this method couldn’t work for an explosion that produces a plume capable of crossing different layers of the atmosphere. According to the researchers, the temperature variations between different layers make it trickier to get accurate results. They adopted an approach involving the parallax method and three satellites to overcome these problems.

The parallax method is based on the principle that when two people in different places look at the same object, they will see it in slightly different places (a common example is that if you see an object with your right eye closed and then with your left eye closed, you’ll observe two different positions of the same object).

In the case of the tonga volcano eruption, it was seen by three satellites, and the difference in where they see the volcanic eruption is based on how high the eruption went. So basically, the researchers used the different altitudes observed by the different satellites to figure out how high the plume went.

Explaining this further, one of the authors and NERC (National Environment Research Council) fellow at Oxford, Dr. Simon Proud, told IE, “We use three satellites here, which really helps make an accurate estimate of the eruption altitude. Previous methods with two satellites can provide good estimates, but for extreme events like this volcano, the addition of a third satellite gives a lot more certainty. Other techniques that don't use parallax didn't work for this volcano, as they rely on comparing the temperature of the eruption plume to that of the atmosphere.”

The researchers calculated that the maximum height of the plumes from the Tonga eruption was 35.4 miles (57 km), breaking the 31-year-old record of Mount Pinatubo plumes that went 40 km high in Earth’s atmosphere on June 15, 1991. Burj Khalifa (the tallest building on Earth) has a height of 0.5 miles (0.8 km). Even if you make a building 68 times taller than Burj Khalifa, its top won’t be able to touch the maximum height up to which the plumes from the Tonga explosion went.

The satellites may have missed the peak

The Tonga eruption is one of the most powerful volcanic events ever recorded in human history. The explosion from this volcano was 500 times more powerful than the nuclear bombs that wreaked havoc on Hiroshima in 1945. Moreover, the amount of water vapor released along with its plume was more than enough to fill 58,000 Olympic-size swimming pools.

The current study's authors believe that the plumes may have gone even above 57 km because the satellites didn’t take pictures of every moment of the eruption. The scan rate of the satellites allows them to take a photo every ten minutes, which means that all the volcanic activity between those ten-minute snapshots is missed.

So it's possible that the eruption reached higher altitudes but that those fell between the snapshots. However, this is still much better than previous eruptions. Interestingly, during the Mount Pinatubo eruption also, the satellites took pictures every 30-60 minutes. So the peak was very likely to be missed there as well.

The researchers are now working on automating their plume altitude estimation process because their parallax method-based technique still requires manual involvement to pinpoint the highest areas.

“We also hope to get extra data to build our methods, merging images from multiple types of satellites, for example. More generally, I think this eruption highlights a very important point: The fact we could see this eruption via satellite less than 10 minutes after it began and then had tools such as ours (and others) to monitor the eruption really shows how modern space technology can help with disaster risk reduction,” said Dr. Proud.

The study is published in the journal Science.