In too deep? The growing threat to the global undersea cable network

Deep sea data cables are the veins of the modern world. What if something, or someone, were to sever them?

- Jonathan Yerushalmy

It was the opening days of 2022, in the aftermath of a huge volcanic eruption, when Tonga went dark. The underwater eruption - 1,000 times more powerful than the bomb that was dropped on Hiroshima - sent tsunami waves across Tonga's nearby archipelago and blanketed the island's white coral sands in ash.

The strength of the eruption severed internet connectivity with Tonga causing a communication blackout.

When the undersea cable that provides the country's internet was restored weeks later, the scale of the disruption was clear. The lack of connectivity had hampered recovery efforts while devastating businesses and local finances, many of which depend on remittances from abroad. The disaster exposed the extreme vulnerabilities of the infrastructure that underpins the workings of the internet.

Contemporary life is inseparable from an operational internet, said Nicole Starosielski, a professor at the University of California, Berkeley and the author of The Undersea Network.

It is much like drinking water - a utility that underpins our existence, but few people understand what it takes for it to travel from a reservoir to our taps. Consumers have come to imagine the internet as something unseen in the atmosphere - an invisible "cloud" raining data on us. Because our devices aren't tethered to any cables, many of us believe the whole thing is wireless, Starosielski said. The reality is far more extraordinary.

Almost all internet traffic-including Zoom calls, movie streams, emails and social media feeds - reaches us via high-speed fibre optics laid on the ocean floor. These are the veins of the modern world, stretching almost 1.5 million km under the sea.

Speaking via WhatsApp, Starosielski explained that the data transmitting her voice travelled from her mobile phone to a nearby phone mast. "That's basically the only wireless hop in the entire system," she said.