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Pacific News Minute: 2021 Tonga eruption breaks record for underwater currents

Hunga Tonga–Hunga Haʻapai eruption on Dec. 30, 2021.
Hunga Tonga–Hunga Haʻapai eruption on Dec. 30, 2021.

Scientists say last year's Tonga volcanic eruption produced the fastest underwater currents ever recorded.

The underwater volcano called Hunga-Tonga Hunga-Ha'apai erupted on Jan. 15, 2021.

Huge amounts of rock, ash and mud were clocked moving across the ocean floor at speeds of up to 75 mph.

These "density currents” snapped long sections of telecommunications cabling, cutting the Pacific kingdom's link to the global internet.

The BBC reported that scientists knew most of the debris thrown into the sky by the volcano must have come back down and spread out across the ocean floor.

Now they've been able to map the flow’s journey and say something about its speed.

They did this by comparing the timing of the eruption with the timing of the underwater cable breaks.

There were two cables operating near the volcano, one connecting Tonga to the internet and the other distributing this service to local islands.

The domestic cable, 31 miles from Hunga-Tonga, was the first to go down, 15 minutes after the start of the eruption. The international cable, about 43 miles away, followed about an hour later.

British researchers say their investigations indicate the flow that broke the local cable must have been moving at up to 75 mph; and even with the international cable being further away, a speed of around 32 mph is realistic.

Derrick Malama is the local anchor of Morning Edition.
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