The undersea volcano that erupted near Tonga on January 15 was “hundreds of times” more powerful than the Hiroshima nuclear explosion, according to NASA.
NASA scientist Jim Garvin, the chief scientist at NASA’s Goddard Space Flight Center, and his colleagues have been observing changes in Tonga landmasses since 2015 when new land rose above the surface of the water and joined two existing islands.
According to Gizmodo, In 2015, new land emerged in the South Pacific, linking a pair of pre-existing islands, Hunga Tonga and Hunga Ha’apai. Shortly after the new land emerged, hotel owner, Gianpiero Orbassano visited the newly formed island,
Orbassano, together with a friend and his son, arrived at one of the island’s three beaches in March 2015 and proceeded to climb to the highest point of the island’s crater, reported ABC.net.au. at the time.
Orbassano, an Italian national living in Tonga, said the island had great potential to attract tourists, despite warnings from scientists that the area could be unstable and dangerous.
Scientists were right about the danger
Close to seven years later, it seems the scientists were right. Hunga-Tonga-Hunga-Ha’apai, as the newly formed island was named, is now a shattered version of its former self, having been obliterated in the January 15 eruption.
“This is a preliminary estimate, but we think the amount of energy released by the eruption was equivalent to somewhere between 4 to 18 megatons of TNT,” said Garvin, according to NBC News, adding, “That number is based on how much was removed, how resistant the rock was, and how high the eruption cloud was blown into the atmosphere at a range of velocities.”
“The blast released hundreds of times the equivalent mechanical energy of the Hiroshima nuclear explosion,” NASA said in a statement. “For comparison, scientists estimate Mount St. Helens exploded in 1980 with 24 megatons and Krakatoa burst in 1883 with 200 megatons of energy,” it said.
The blast was heard as far away as Alaska and was probably one of the loudest events to occur on Earth in over a century, according to Michael Poland, a geophysicist with the U.S. Geological Survey reports NPR.org.
“This might be the loudest eruption since [the eruption of the Indonesian volcano] Krakatau in 1883,” Poland says. That massive 19th-century eruption killed thousands and released so much ash that it cast much of the region into darkness.
Hunga Tonga-Hunga Ha’apai was completely destroyed by Saturday’s explosion, says Dan Slayback, a research scientist for NASA’s Goddard, as well as Science Systems and Applications Inc.
Slayback says the blast was so massive it even appears to have taken chunks out of the older islands nearby. “They weren’t ash – they were solid rock, blown to bits,” he says. “It was quite amazing to see that happen.”
Evidence for calling the explosion an “ultra Surtseyan” eruption
Polland says that despite its explosive force, the eruption itself was actually relatively small. Unlike the 1991 eruption of Mount Pinatubo, which spewed ash and smoke for hours, the events at Hunga Tonga-Hunga Ha’apai lasted less than 60 minutes.
The real mystery, according to Polland, is how such a relatively small eruption could create such a big bang and tsunami. “It had an outsized impact, well beyond the area that you would have expected if this had been completely above water,” he says. “That’s the thing that’s just a head-scratcher.”
What was different about this eruption? Gavin told Gizmodo: “We don’t have any seismometers on Hunga Tonga-Hunga Ha’apai—but something must have weakened the hard rock in the foundation and caused a partial collapse of the caldera’s northern rim.”
“Think of that as the bottom of the pan dropping out, allowing huge amounts of water (at about 68 degrees F) to rush into an underground magma chamber whose magma measures upwards of 1,832 degrees F.”
Perhaps because of all that water, the explosion was far more powerful than normal. Garvin and his peers have been referencing the resulting explosion as an “ultra Surtseyan” eruption—and one that wiped Hunga Tonga-Hunga Ha’apai off the map.
