Earthquake News

'Super Spectacular,'  How the Tonga Volcano triggered a once-in-a-century seismic event.

Physical oceanographer, Angel Amores of the Mediterranean Institute for Advanced Studies in Spain, said the shockwave took approximately 36 hours to circle the earth. It traveled at the speed of sound and spread in concentric rings from the Hunga Tonga, Hunga Haapai volcano.

In March, the simulation was published in Geophysical Research Letters. Amores was reviewing data from neighboring meteorological stations from his home when he first noticed the wave's characteristic. When the shock wave made its first pass over Mallorca, roughly 15 hours after the eruption, local equipment detected significant pressure changes. 

"Then I waited and said, OK, it'll take about 36 hours to get back," he explained. "And then it went away." It passed for the third time after another 36 hours.

He said, "This is the first time I've seen something like that."

The shockwave, which raced around the earth several times at the speed of sound, was described as "It’s super spectacular” by Peter W. Brown, a physicist at the University of Western Ontario. "Everybody who studies atmospheric waves are all quite, I would say, awe-struck."

Weathernews, a Japanese firm, operates a network of tens of thousands of low-cost weather sensors that collect data every minute. As the shockwave passed, many of their sensors noticed virtually simultaneous spikes in air pressure.

As the wave passed, weather stations all across the world observed comparable pressure rises, including those in the United States, the United Kingdom, Germany, India, China, and Australia. The shockwave generated minor changes in local air variables such as water vapor temperature as it moved, leaving tiny ripples visible in satellite photographs and video footage from a Hawaii observatory.

Shockwaves are caused by rapid movement compressing the surrounding material, which in this case was air, according to Mark Boslough, a physicist at New Mexico's Los Alamos National Laboratory.

Dr. Boslough explained, "You've got a compression wave moving into a material, and it's moving quicker than the substance can get out of the way." "As a result, everything starts to pile up." 

When an aircraft reaches and then exceeds the speed of sound (approximately 650 miles per hour (ca. 1,046 km/h) at cruising altitude for a jet), a sonic boom is produced by the buildup of compressed air molecules.

A sonic boom, on the other hand, is a limited event that occurs for a few seconds on the ground along a route that is at most 50 miles (ca. 80 kilometers) broad. The Tonga explosion was so massive that it sent shockwaves all over the world.

Dr. Boslough described the event as "a massive global sonic boom."

According to Greg Dusek, a physical oceanographer and head scientist of the NOAA division that monitors ocean tides, the tsunami hit during high tide in some Pacific areas, resulting in the highest water levels since the 1950s. 

The eruption occurred underwater at a depth of less than 1,000 feet (0.3 kilometers) in very hot weather magma rushed up and out of the volcano, is currently being studied by volcanologists. On its own, the rapid expansion of carbon dioxide and other gases in magma would be an extremely explosive event. The magma, on the other hand, interacted aggressively with the salt water, causing it to explode into steam.

A plume of hot gases and ash ascended well over 20 miles into the atmosphere.
The plume rose to a height of 36 miles, passing through the stratosphere, the atmosphere's topmost layer.
The plume was "perhaps the highest ever recorded by satellites," according to a NASA analysis. According to a NASA, the plume was "perhaps the highest ever recorded by satellites." 

The sort of shockwave produced by the explosion is known as a Lamb wave, named after Horace Lamb, a British mathematician who originally characterized it in the early twentieth century.
Dr. Brown explained that "it's really only there when there's a really massive explosion," one that "may make the entire atmosphere really resonate like a bell."

Dr. Amores and other scientists examining it have never seen anything like it before, because the last time there were explosions this large was decades ago, when the US, the Soviet Union, and other countries conducted atmospheric nuclear weapons tests.
Above-ground testing were mostly outlawed in the early 1960s, while a few small ones continued until 1980. 

According to Dr. Brown, the Lamb wave produced by the eruption was comparable in size to one generated by the greatest atmospheric test ever done, this involved a Soviet weapon known as "Tsar Bomba." In 1961, it was detonated above the Soviet Arctic, releasing energy equivalent to around 50 million tons of TNT, or 50 megatons.

According to Dr. Brown, the Tonga explosion discharged far more energy than that. "We can say it with ease."

The changes in atmospheric pressure measured as the wave went around the Earth were minor, with deviations from normal pressure of less than 1%. But, according to Dr. Brown, the alterations lasted for tens of minutes.

This resulted in a different type of tsunami, known as a meteotsunami, in areas far away from the volcano. Fast-moving weather systems are the most common cause of tsunamis, but under the correct conditions, a change in air pressure above a lake or other body of water can cause potentially damaging waves to form.

Meteotsunamis were observed in Japan following the eruption, arriving hours before the "classic" tsunami waves caused by saltwater displacement arrived. This is due to the fact that the pressure wave in the atmosphere moved quicker than the Pacific tsunami.

Meteotsunamis have been seen in the Caribbean and even the Mediterranean, far from the Pacific.

When the pressure wave passed Charlotte Amalie, in the US Virgin Islands, some 8,000 miles away from the Tonga volcano, for example...

Dr. Dusek's colleagues at NOAA were taken aback when they discovered the signal of a tsunami in the Caribbean.
He explained, "We were like, wow, it doesn't seem likely."
"What we found was that it happened right after this pressure wave or shockwave arrived."

Dr. Dusek's colleagues at NOAA were taken aback when they discovered the signal of a tsunami in the Caribbean. He explained, "We were like, wow, it doesn't seem likely. "What we found was that it happened right after this pressure wave or shockwave arrived. Dr. Dusek believes this is the first time since Krakatau's massive eruption in 1883 that an eruption has caused a global shockwave, which has caused ocean waves in harbors throughout the world. The Krakatau shockwave was detected by barometers all around the world and circled the globe at least three times, shattering the eardrums of sailors on a ship 40 miles away. "However, this is the first time we've seen it in real time," the author explains.

The shockwave gradually degraded, as all waves do, according to Dr. Boslough.
"As the compression wave knocks molecules together, a little energy is pulled out by heating up the air," he explained.
"As a result, they eventually fade out, just as sound waves don't travel indefinitely."

Dr. Boslough's main interest is on preventing collisions with items from space, such as an asteroid explosion in the atmosphere.

The explosion in Tonga is "quite closely related," according to experts.

Dr. Boslough is working on a model of the explosion.
"This is a once-in-a-lifetime chance," he remarked.
"One of the reasons we're working on this is because of its connection to planetary defense and our understanding of what a large shockwave in the atmosphere can do to the Earth." 

 

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