Hunga Tonga–Hunga Ha‘apai, an underwater volcano off the coast of Tonga, has erupted several times in the last 13 years, but the most recent, on January 15, was likely its most destructive. The blast has had global consequences: more than 6,000 miles away, waves caused by the eruption drowned two people in Peru.

But the effect of the volcanic blast on Tongans living closer to ground zero isn’t yet known, though it’s feared that the ensuing tsunami may have killed many people and displaced many more from their homes. That’s because Tonga has been suddenly cut off from the internet, making it that much harder to coordinate aid or rescue missions. In a highly interconnected world, Tonga is now completely dark, and it’s almost impossible to get word out. Getting the country back online is vital—but it could take weeks.

Internet traffic plunged to near-nothing around 5:30 p.m. local time on January 15, according to data from web performance firm Cloudflare. That connection hasn’t yet been restored, says Doug Madory of Kentik, an internet observatory company, who has been monitoring the country’s web traffic.

The reason Tonga fell offline isn’t yet known for certain, but initial investigations have suggested that the undersea cable connecting its internet to the rest of the world has been destroyed by the blast.

“Tonga primarily uses a single subsea cable to connect to the internet,” says Madory. The Tonga Cable System runs 514 miles between Tonga and Fiji, bringing internet service to the two island nations. Previously, that connection has been backed up by a satellite internet connection. “I guess they’re not able to do that this time, because of some technical failure preventing them from being able to switch over,” says Madory. He believes that the wave resulting from the volcano explosion could have taken out the satellite dishes.

Jamaica-based mobile network operator Digicel, which owns a minority stake in the cable alongside the Tongan government, said in a statement: “All communication to the outside world in Tonga is affected due to damage.” Southern Cross Cable, a New Zealand–based company that runs cables interconnecting with the Tonga Cable System, believes there’s a possible break around 23 miles offshore. It’s also believed that the domestic subsea cable is broken around 30 miles from Tonga’s capital, Nukuʻalofa. Such breaks are usually found by sending light down the fiber-optic core of the cabling and calculating how long it takes for the signal to bounce back—which it does when interrupted, says Christian Kaufmann, vice president of network technology at content delivery network Akamai.

If that’s confirmed, it’s just about the worst possible news for Tonga’s connectivity. “It will be days—maybe weeks—before the cable is fixed,” says Madory.

The outage isn’t the first time that Tonga’s internet infrastructure has been plagued with problems. In January 2019, the country experienced a “near-total” internet blackout when an undersea cable was cut. Initial reports indicated that a magnetic storm and lightning may have damaged the connection—but a subsequent investigationfound that a Turkish-flagged ship dropping anchor had severed the line. Fixing the issue cost an estimated $200,000, and while it was being fixed, the island relied on satellite internet connections.

Those same satellite connections are likely to be the only savior for Tonga’s internet in the near term—but with unknown damage to them, the country could be in for a difficult period. “They were probably thinking: ‘Well, if the cable goes down, we have the satellites for resilience,’” says Madory. “If a volcano detonates right next to you and takes out both your cable and your satellite, there’s not much you can do.” Huge amounts of ash thrown up into the air by the eruption could also be affecting satellite connectivity, says Kaufmann.

Fixing the broken cable won’t be easy. Specialized shipping vessels tasked with fixing breakages—which occur every week somewhere around the world, albeit with less force than is likely to have resulted from the eruption—need to be sent to the site of the problem. One vessel that could help is the CS Resilience, currently off Papua New Guinea, nearly 3,000 miles away. It’s estimated that any vessel could take days or weeks to remedy the issue.

“There’s a priority over whose cable gets fixed first,” says Madory. “Countries pay a little premium to get fixed first.” Once one of these vessels arrives on scene, which itself could take days, it drops a hook to snag the cable that runs along the sea floor. The hooked cable, which when in the deep ocean can be as thin as a common garden hose, is then winched up onto the deck of the vessel, where technicians work to fix the break. “The cabling itself is not the most sturdy thing,” says Kaufmann. It’s then lowered gently back into the water. “That process hasn’t changed much in the 150 years or so that we’ve had submarine cables,” says Madory.

There are, of course, compounding factors that can complicate the process. Tonga is likely to be besieged by vessels looking to deliver aid to the country, which may mean internet cabling takes a back seat to saving lives, restoring power, and delivering vital food and water supplies. The precise location of the rupture can also make things complicated: generally, the further out the break is from shore, the deeper the cable—and the harder it is to reach and drag up from the floor. That’s before considering that the onshore power lines that help keep the connection online may well be damaged beyond easy repair. “Tonga is on an extremity of the internet,” says Madory. “Once you go out from the core of the internet, you’re just going to have fewer options.”

The internet outage shows how dependent the world’s internet connectivity can be on single points of failure. “It’s one of those stories that put the lie to the idea that the internet was designed to withstand nuclear wars,” says Alan Woodward, a professor of cybersecurity at the University of Surrey in the UK. “Chewing gum holds most of it together.” Woodward suggests that rare physical events such as volcanic explosions are difficult to design for, but countries should try to maintain redundancy through multiple undersea connections, and ideally ones that follow different routes so that a localized incident won’t affect multiple lines. 

Yet redundancy doesn’t come cheap—especially for a small nation of just over 100,000 people like Tonga. It’s also likely that with a massive eruption such as this one, the movement of the seabed would have caused a fissure in any secondary cable, even if it was laid on the other side of Tonga. 

“There’s a broader message around the resilience of infrastructure,” says Andrew Bennett, who analyzes internet policy at the Tony Blair Institute for Global Change. “Although the UK or US isn’t going to be like Tonga, increasingly there are geopolitical tensions and debate[around] discussing things like undersea cables that are pushing us into a more fractious place. You don’t want to end up in a place where you have sovereign cables for the allies and other cables for everyone else.”

Bennett suggests two options to bridge the connectivity gap. One is rapid rollout of satellite internet—and the satellite constellations are being launched into space as we speak. The other is to devote more money to the problem. “If you look at resilient internet infrastructure as a public good, countries who can afford it should pay for it and provide it to others,” he says. Closing the global digital divide by 2030 would cost just 0.2% of the gross national income of OECD countries per year, according to the institute.

Given that the internet is increasingly seen as a fourth vital service, alongside heat, power, and water, such a long outage for 100,000 people is a major disaster—compounding the immediate physical effects of the eruption. And it highlights the fragility of certain parts of the internet, particularly outside the rich Western world. “The internet’s not necessarily crumbling at the core,” says Woodward. “But it’s always going to be a little frayed around the edges.”