The island nation of Tonga’s internet blackout will likely continue for weeks after an underwater volcanic eruption damaged its subsea communications cable.

Tonga has been cut off from the outside world since the explosion of the underwater Hunga Tonga-Hunga Ha’apai volcano, which knocked out communications, killed at least three people and sent tsunami waves across the Pacific.

The massive eruption was recorded around the world and heard as far away as Alaska, triggering a tsunami that flooded Pacific coastlines from Japan to the United States. Despite being underwater, the eruption was large enough to be visible from space.

1.14.2021: Large volcanic eruption near Tonga (Hunga Tonga-Hunga Ha’apai volcano) today as seen from outer space. Shown on visible imagery using the Himawari satellite. #hiwx #tsunami #earthquake pic.twitter.com/zOTj6Qu1Wv

— NWSHonolulu (@NWSHonolulu) January 15, 2022

It is believed that the underwater eruption caused damage to the 827km long subsea cable between Tonga and Fiji, the nation’s main source of internet connection. The cable owner, Tonga Cable Ltd, said the damage is 37km from Nuku’alofa for its international connection and 47km out for its domestic connection.

Telecom operator Digicel said telephone links have been restored between Tonga and the rest of the world, though Reuters reported it was unable to immediately reach numbers in the island nation. Digicel is using a local satellite dish on the main island to restore domestic 2G calls, but restoring full internet connectivity is expected to take far longer.

“US cable company SubCom advises it will take at least four weeks for Tonga’s cable connection to be repaired,” New Zealand’s foreign ministry said on Wednesday 19 January, The Journal reported.

A specialist ship, the CS Reliance, plans to embark on a repair mission to fix the undersea cable. But the unknown scale of cable damage along with a journey to the dangerous fault area means repair times could take longer than a month.

“The cables are actually around the volcanic zone. We don’t know … whether they are intact or blown away or stuck somewhere underwater. We don’t know if it’s buried even deeper,” chairman of Tonga Cable Samiuela Fonua told Reuters.

The communications blackout has made relief efforts more difficult, highlighting a vulnerability of subsea fibre-optic cables which have become a vital network for data travelling around the globe. Without the cable, countries have been relying on satellite phone connections, surveillance flights and satellite images to measure the full scale of the disaster.

In 2011 the World Bank Group and the Asian Development Bank announced that they would fund a new submarine cable to Tonga. The $34 million cable was completed in 2018 and greatly boosted Tonga’s internet speeds, but it is the nation’s primary connection to the outside world.

According to internet observation company Kentik, connecting remote island nations with high-speed access is a great challenge. Without a subsea cable, these locations are reliant on expensive satellite service which suffers from latency and capacity issues. These locations are also small for investment returns, meaning private investors usually avoid them.

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