Tonga volcanic eruption largest ever recorded
WELLINGTON: A deadly volcanic eruption near Tonga in January was the largest ever recorded with modern equipment, a New Zealand-led team of scientists revealed on Monday.
The Hunga Tonga-Hunga Ha’apai volcano erupted underwater with a force equivalent to hundreds of atomic bombs, unleashing a 15-meter (50-foot) tsunami that demolished homes and killed at least three people on the Pacific island kingdom.
The natural disaster also damaged undersea communication cables, cutting Tonga off from the rest of the world for weeks and hampering efforts to help the victims.
A detailed study by New Zealand’s national institute for water and atmospheric research shows the eruption blasted out almost 10 cubic kilometers of material — equivalent to 2.6 million Olympicsized swimming pools — and fired debris more than 40 km (25 miles) into the mesosphere, the level above the Earth’s stratosphere.
“The eruption reached record heights, being the first we’ve ever seen to break through into the mesosphere,” marine geologist Kevin Mackay said. “It was like a shotgun blast directly into the sky.”
The Hunga Tonga-Hunga Ha’apai eruption rivals the infamous Krakatoa disaster, which killed tens of thousands in Indonesia in 1883 before the invention of modern measuring equipment.
“While this eruption was large — one of the biggest since Krakatoa — the difference here is that it’s an underwater volcano and it’s also part of the reason we got such big tsunami waves,” Mackay said.
The team of scientists has accounted for three-quarters of the material fired out by the Tongan eruption with the rest explained as debris scattered in the atmosphere.
Mackay said the plume was estimated to have contained nearly 2 km3 of particles that stayed in the atmosphere for “months, causing the stunning sunsets we saw” across the Pacific region as far away as New Zealand.
His team also discovered that the volcano’s crater is now 700 m deeper than it was.
The eruption’s pyroclastic flows — deadly currents of lava, volcanic ash and gases that reach temperatures of 1,000 degrees Centigrade (1,800 degrees Fahrenheit) and speeds of 700 km an hour — carried debris from the volcano along the sea floor at least 80 km away.
“But the pyroclastic flows appear to extend beyond that, perhaps as far as 100 km away,” said Emily Lane, the team’s principal scientist.
“The sheer force of the flows is astonishing — we saw deposits in valleys beyond the volcano, meaning they had enough power to flow uphill over huge ridges and then back down again.”