The power of the eruption that took place on Saturday is estimated by NASA researchers.
James Garvin, the chief scientist at NASA's Goddard Space Flight Center, told NPR that they came up with a number that's 10 megaton equivalent.
The bomb dropped on Hiroshima was 500 times more powerful than the one that was dropped.
The blast was heard as far away as Alaska, and was probably one of the loudest events on the planet in the last century.
Poland says that this might be the most powerful eruption since the Krakatau eruption in 1883. The 19th century eruption killed thousands and released so much ash that it cast much of the region into darkness.
The worst may be over for now, according to Garvin.
"If the past precedent for volcanic eruptions in this kind of setting has any meaning at all, then we won't have another one of these explosions for a while," he said.
Three days after the blast, the island is largely cut off from the world. Relief flights are not allowed to land at the capital city of NukualoFA because the airport is covered in ash.
Houses and other structures were blanketed by ash from New Zealand. The New Zealand foreign ministry reported that a wave had hit the western coast of the main island of Tongatapu, killing two people and causing major damage. The Mango island, where all homes have been destroyed, is one of the outlying islands that the Government of Tonga claims has been damaged.
An aerial view of the island of Nomuka in the Pacific. The extent of the damage to the island nation is unknown.
The New Zealand Defence Force.
The NASA team studied the volcano behind the eruption for years. The islands that make up Tonga are located along a subduction zone, where one part of the earth's crust dips under another.
"In this case, we don't know when a volcano with a big summit ring of hills formed," says Garvin.
The caldera's volcanic activity created a platform that rose up out of the sea. The island was covered in steam and ash and connected to two other islands.
Dan Slayback, a research scientist for NASA, says that the explosion destroyed the entire island.
He says that they were solid rock, blown to bits. It was amazing to see that happen.
The formation of the Island probably caused its destruction. As it rose from the sea, there was a network of chambers beneath it. He thinks the explosion was caused by a change in the plumbing in the underground.
He says that when you put a ton of seawater into a small area of liquid rock things are going to get bad fast.
Michael Poland, a scientist with the US Geological Survey, said that the eruption was relatively small. The 1991 eruption of Mt. was different. The events at Hunga Tonga Hunga Ha'apai lasted less than an hour. He doesn't think the eruption will cause any short-term changes to Earth's climate.
Poland says that the real mystery is how a relatively small eruption could create a big bang.
"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 scratcher.
Scientists want to do more surveys around the volcano caldera. Satellite imagery analysis is already underway, and may soon be followed by missions by uncrewed drones. He hopes the volcano will be safe for researchers to visit later in the year.
Poland believes that researchers will learn a lot more in the coming months as they conduct new surveys.
He says that the event is terrible for the people of the island. It could be a benchmark event in volcanology.