'Rapid bang': Kiwis hear Tongan volcano erupt from thousands of kilometres away

Sunday, 16 January 2022

The massive volcanic eruption near Tonga was heard thousands of kilometres away by people across New Zealand, according to GNS Science.

The underwater volcano erupted about 5pm on Saturday. Kiwis started calling GNS Science from across New Zealand with reports of a loud boom about 7pm. The reports coincided with signals picked up by the Crown science agency’s acoustic monitoring network.

The Hunga-Tonga-Hunga-Ha'apai volcano is more than 2000 kilometres away from New Zealand.

GNS Science volcanologist Geoff Kilgour said it was unusual for a volcanic eruption to be heard from such a large distance.

**READ MORE:

* Tonga volcano: Concern for 8000 people in the Ha'apai group as communication lines still down

* Why the volcanic eruption in Tonga was so violent, and what to expect next

* Underwater volcano Hunga-Tonga-Hunga-Ha'apai erupts again

**

“It is so rare for people to hear it from so far away,’’ he said.

“People hearing these sorts of sounds from so far away is very rarely recorded, it is only a few times in history.

“For this to happen you need a huge explosion. You can’t have an eruption that builds slowly. It has to be a rapid bang and a huge amount of energy released all at once.”

The volcanic explosion was 'by far the most violent eruption that we have seen in some time”, he said.

The last time a volcano had exploded so violently was Pinatubo in the Philippines in 1991, he said.

He said the volcano could be heard from such a large distance because the explosion was so big, low frequency bass sounds travel a long way and there was little between New Zealand and Tonga to baffle the noise.

“It is just a flat ocean.”

Reports of people hearing the sound across New Zealand came in to GNS Science about the same time as the eruption was measured on their acoustic sensors about 7pm on Saturday.

The sound of the eruption took about two hours to reach New Zealand.

“We saw it on our monitoring network which connected with when people were telling us they were hearing it.”

He said measuring stations around the world had picked up the volcanic explosion on instruments that measure sounds that cannot be heard by people.

“There are some colleagues in Iceland that have seen the lower frequency acoustic signals on their instruments.

“It has travelled around the world.”