(ORDO NEWS) — An indicator of the enormous force of the eruption of the Tonga volcano last Saturday is the height to which its plume rose.
According to the calculations of British scientists studying data from meteorological satellites, it is located at an altitude of about 55 km (35 miles) above the Earth‘s surface.
It is at the boundary of the layers of the stratosphere and mesosphere in the atmosphere.
Dr. Simon Proud of RAL Space said these are “unheard of heights” for a volcanic plume.
The most powerful eruption in the second half of the 20th century occurred at Mount Pinatubo in 1991. It is believed that its plume rose to a height of about 40 km.
However, it is possible that today’s more accurate satellites would give a higher eruption height in the Philippines, warns Dr Proud of the UK‘s National Earth Observatory.
To determine the position in the sky of the plume from the Hunga-Tonga-Khapai volcano in Tonga, data from three meteorological satellites – Himawari-8 (Japan), GOES-17 (USA) and GK2A (Korea) were used.
“Because they are all at different longitudes, we can use the parallax between their eruption modes to determine the height. This is a fairly well-established technique for determining the height of thunderclouds, and in this case it should work better, since the height [and therefore parallax] more,” Proud told BBC News.
It can be seen that only a small part of the cloud reaches a height of 55 km. This is most likely water vapor and not ash that was pushed up by the updraft. The main plume umbrella is located at an altitude of 35 km. In the lowest layer of the atmosphere – the troposphere – the lower line of the plume is visible.
The so-called Karman line, which is often referred to as the boundary of the atmosphere with space, is located at an altitude of 100 km.
US space agency scientists have calculated that the force of the explosion was equivalent to 10 megatons of TNT, which would have made the Tonga event 500 times more powerful than the nuclear bomb dropped on Hiroshima, Japan, at the end of World War II.
Professor Shane Cronin from the University of Auckland (New Zealand) believes that a special set of conditions has developed in an underwater volcano that contributed to a powerful explosion.
The key factor, he said, was the depth below the ocean’s surface, at which the gas-rich magma came into contact with seawater – only 150-250 meters.
When the magma came out, there wasn’t much pressure [from the water] on it,” he said on World Radio’s Science in Action program.
“The gases expanded and tore the magma apart. And then when these little pieces of hot magma at 1100 degrees collided with cold sea water at 20 degrees, the sea water around these particles turned into steam. And when you do this, when you turn water into steam, you are essentially increasing the volume by a factor of 70. So you amplify the eruption.”
According to early data, the eruption in Tonga could reach five points on the volcanic explosive index (VEI). This would certainly make it the most powerful eruption since Pinatubo, which was classified as six on an eight-point scale.
The Philippine volcano is famous for lowering the average global temperature on Earth by half a degree for several years. He did this by releasing 15 million tons of sulfur dioxide into the atmosphere. SO2 combines with water to form a haze of tiny droplets, or aerosols, that reflect incoming solar radiation.
However, Dr Richard Betts, head of climate impacts at the UK Met Office, said Hunga-Tonga-Hapai would not have the same effect.
“Pinatubo did have a noticeable effect, but the Hunga Tonga volcano emissions were over 30 times smaller – less than half a million tons of sulfur dioxide, so we don’t expect it to have a cooling effect, although it produced a huge explosion when it exploded,” he explained. he.
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