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A lone undersea internet cable connected Tonga to the world — a volcanic eruption broke it

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A stark demonstration of the fragility of the modern web

Satellite Images Show Before/After Hunga Tonga-Hunga Ha’apai Volcano Eruption
The Hunga Tonga-Hunga Ha’apai volcano(pictured here on January 6th) erupted on January 14th.
Photo by Maxar via Getty Images

The effects of a colossal volcanic eruption in the Pacific archipelago of Tonga are still being calculated, but one consequence is clear: Tonga has been cut off from the internet, after the lone undersea cable that connects the country to the rest of the web was damaged during the eruption.

Like many island nations, Tonga relies on just a single undersea cable, about the thickness of a garden hose and filled with fragile fiber-optic filaments, to get citizens online. But on Tuesday, the government of Tonga said “communications both international and domestic were severed due to damage sustained by the submarine cable.”

The government added that “limited communication” was possible through satellite phones and high-frequency radio, but these constraints are making it difficult to assess the damage caused by the January 14th eruption. The Tongan government has reported three fatalities as a result of a tsunami created by the volcano, which erupted on an uninhabited island.

According to Reuters, the internet cable that joined Tonga to the web is 827 kilometers (514 miles) long and secured via a relay on Fiji, Tonga’s second-nearest neighbor. Fixing the cable could take as long as two weeks, as the work requires the intervention of a specialist undersea cable repair ship.

Workers haul part of a fibre optic cable
Undersea cables like this one, being laid in the Kenyan port town of Mombasa, carry 99 percent of international internet traffic.
Credit: STRINGER/AFP via Getty Images

The nearest such vessel is the Reliance, owned by US firm SubCom. But it is currently moored some 4,700 kilometers (2,920 miles) away in Papua New Guinea, and will take days to travel to Tonga. According to Craige Sloots, a marketing and sales director at Southern Cross Cable Network, a company that maintains a number of undersea cables in the region, that means it could take two weeks in total for Tonga’s internet connection to be repaired.

“Its ability to repair would also be dependent, as you would expect, on any volcanic activity,” Sloots told Reuters.

The incident is a vivid demonstration of the fragility of modern internet. Although we think of the web as a dense network with numerous redundancies, the truth is that it contains many single points of failure. In the West, this is most obvious when huge web outages are caused by disruptions from centralized services like Amazon Web Services — a subsidiary of Amazon that supplies servers and computing power to the world’s biggest companies.

For countries like Tonga, though, undersea cables are a more obvious bottleneck. Currently, 99 percent of international internet traffic is carried through such undersea cables, with an estimated 436 cables spanning distances of 1.3 million kilometers. But while countries like the US are serviced by multiple lines, poorer nations like Tonga have to rely on just one.

It’s notable that Tonga was actually hit by a similar internet blackout in 2019, and, as a result, signed a 15-year deal with an internet satellite company to protect against future failures. But according to a report from ZDNet, the terms of the contract with provider Kacific were disputed and, as a result, satellite connectivity was never activated.

Now, Tongans must wait for their internet to be repaired by hand. Such repairs are not unusual on a global scale— an undersea cable breaks roughly every two weeks — but they are time-consuming. Technicians on a specialist repair vessel will have to locate the fault in Tonga’s cable by sending pulses of light down the line and timing how long it takes for the pulse to return. They will then have to sail to the location of the breakage and, depending on the depth of the water, retrieve the cable using diving robots or grappling hooks. The cable will then be brought to the surface and repaired by engineers onboard the ship.