NASA researchers have an estimate of the power of a massive volcanic eruption that took place on Saturday near the island nation of Tonga.

"We come up with a number that's around 10 megatons of TNT equivalent," James Garvin, the chief scientist at NASA's Goddard Space Flight Center, told NPR. //

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." //

He suspects the explosion was triggered by a sudden change in the subterranean plumbing, which caused seawater to flood in.

"When you put a ton of seawater into a cubic kilometer of liquid rock, things are going to get bad fast," he says.