The eruption in Tonga was more powerful than the Hiroshima bomb, according to NASA

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The volcanic eruption in Tonga that triggered a tsunami was hundreds of times more powerful than the atomic bomb the United States dropped on Hiroshima during World War II, NASA said.

The eruption “erased” a volcanic island north of the Tongan capital Nuku’alofa, the agency added.

Tonga says that more than four-fifths of the population has been affected by the tsunami and ashfall.

The death of three people in last week’s tsunami was also confirmed.

Before the eruption, the volcanic island known as Hunga Tonga-Hunga Ha’apai consisted of two separate islands joined by new land formed in 2015.

NASA noted that the eruption was so powerful that the new earth disappeared, along with “big chunks” of the two oldest islands.

An “ultrasurtseyan” explosion

Jim Garvin, chief scientist at NASA’s Goddard Space Flight Center, had been studying new land formation from eruptions at Hunga Tonga-Hunga Ha’apai since 2015 with his colleagues.

The island is the highest part of a large submarine volcano that rises 1.8 kilometers from the ocean floor, is 20 kilometers wide, and is crowned by a 5-kilometer-diameter submarine caldera.

“This is a preliminary estimate, but we believe that the amount of energy released by the eruption was equivalent to between 4 and 18 megatons of TNT,” Garvin said, as reported by NASA.

“That number is based on how much soil was removed, how strong the rock was, and how tall the eruption cloud was that was thrown into the atmosphere at a range of velocities.”

The explosion released hundreds of times the mechanical energy equivalent to the Hiroshima nuclear explosion.

For comparison, scientists estimate that Mount St. Helens exploded in 1980 with 24 megatons and Krakatoa in 1883 with 200 megatons of energy.

The explosions of January 15 dropped material at a height of up to 40 kilometers and possibly up to 50 kilometers, covering nearby islands with ash and triggering destructive tsunami waves. An astronaut aboard the International Space Station took a photo of the ash over the South Pacific.

NASA explained that the temperature or magma usually exceeds 1,000 degrees Celsius, while seawater is closer to 20°C.

The mix of the two can be incredibly explosive, particularly in the confined space of a magma chamber.

“This was not a standard Surtseyan eruption because of the large amount of water that had to be involved,” Garvin said.

Garvin stated that some of his colleagues in volcanology “think this type of event deserves its own designation. For now, we are unofficially calling it an ‘ultrasurtseyan’ eruption.”

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NASA had been monitoring since 2015 the formation by eruptions of new land like the one in the image, which had joined two islands in the Tonga archipelago.

Emergency in Tonga

The widespread release of volcanic ash, gases and particles from the eruption remains a major challenge for Tongan authorities.

In the immediate aftermath of the eruption and tsunami, it was feared that water sources had been contaminated by the thick layer of ash, increasing the risk of diseases such as cholera and diarrhoea.

However, local officials said tests taken in recent days showed the groundwater and rainwater to be safe to drink.

But nevertheless, fine volcanic ash continues to pose a public health risk. Exposure to these particles could cause breathing difficulties, affect the cardiovascular system, and irritate the lungs, eyes, and skin.

The government said 62 people on Mango, one of the hardest-hit islands, had to be relocated to Nomuka Island “after losing their homes and all their personal belongings.”

However, authorities clarified that many of those residents could be moved back to the main island, Tongatapu, due to lack of food and supplies.

The government added that there were fewer than two dozen injured, mostly from Nomuka. The clinic on this island was swept away by the tsunami and rescuers had to set up a field hospital.

Foreign-aid ships and planes have been arriving in Tonga since last week, after locals were finally able to clear the island’s only airport runway.

New Zealand and Australia have led the international response, using their air force and naval aircraft carriers to make contactless deliveries of supplies such as water, food, hygiene products and tents, as well as telecommunications repair and water treatment equipment.

The remote archipelago was cut off for five days as the blasts severed the only fiber-optic maritime cable that carries internet to the island.

In the past week an irregular telephone line was restored, which allowed “limited international phone calls.”

But even communication between Tongatapu, the main island, and the outer islands of the archipelago remains “a major challenge”, according to a Tonga government statement.

The arrival of foreign aid has greatly accelerated the flow of information from the affected island.

Due to covid fears, relief work is still carried out by residents through groups such as the Red Cross. Tonga, which is free of covid-19, has requested that no foreign aid workers land in the country to prevent an outbreak.

However, the UN representative in the region, Sione Hufanga, told the BBC that could change given the extent of the damage.


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