Malacca Strait: How one volcano could trigger world chaos
Every year, approximately 90,000 ships pass through the narrow sea lane of the Malacca Strait, which links the Indian Ocean to the Pacific. Their cargo – grain, crude oil, and every other commodity under the Sun – comprises an estimated 40% of global trade. Above these ships is one of the busiest air routes in the world, and below them, running along the seabed, is a dense array of submarine internet cables that keep the world online.
Together, these factors make the Malacca Strait one of the most vital arteries of the global economy. It has been classified as a trade choke point in reports by the World Trade Organization, the US Energy Information Administration and Chatham House, the London-based foreign affairs think-tank.
All of which is to say: nice strait you’ve got there. Be a shame if something… happened to it.
Researchers are warning that it’s only a matter of time before a natural disaster like an earthquake or volcano strikes the region – and when it does, we can expect global consequences.
Disruption of key trade routes is a well-established problem, due to crime or human error. Piracy has long bedevilled the area, but the strait, cooperatively policed by Indonesia, Malaysia, Singapore, and Thailand, is generally under control. Still, it is not uncommon for ships to collide here: 10 American sailors died as a result of the USS John McCain running into a Liberian-flagged tanker in 2017. But at 1.7 miles (2.7 km) at its narrowest, the strait is not slender enough to be blocked by an errant container ship in the way that the Suez Canal was by the 400m (1,312ft) Ever Given in 2021.
The greatest menaces to the Malacca Strait, which separates the Malay Peninsula from the Indonesian island of Sumatra, lie in the natural world. Of the many intriguing maps of activity in the region, the most arresting is the one that collates the world’s active volcanoes and recent earthquakes. Along the coast of Sumatra and the more southerly part of Java, following the course of the Sunda Trench, is a band of earthquake activity, and several volcanoes.
On Java, two volcanoes, Semeru and Merapi, have recently erupted. In the Sunda Strait, which separates Java from Sumatra, is Krakatoa, and further west is Tambora, whose eruption in 1815 caused crop failure as far afield as in Europe and the eastern United States.
The Tambora eruption was magnitude VEI7 in the Volcanic Explosivity Index (VEI), on a logarithmic scale going up to VEI8. An event like 1815 might occur once or twice per millennium. But an eruption need not be of quite so high a magnitude to cause severe problems at a global choke point.
In 2018, researchers at the University of Cambridge’s Centre for Risk Studies envisaged the effects of scenarios including a VEI6 eruption at Marapi. The eruption, they suggested, might produce ash clouds and fine tephra – fragments of rock ejected into the air – that waft across the Malacca Strait towards Singapore and Malaysia. The resultant damage to local infrastructure and supply chains, with aviation particularly badly affected, would combine with a global temperature drop of 1C to wipe an estimated $2.51tn (£2tn/€2.3tn) off global GDP over a five-year period. That figure dwarfs the estimated $5bn (£4bn/€4.6bn) that the VEI4 eruption of Eyjafjallajökull, in Iceland, wiped from the global economy.
Marapi’s last VEI4 eruption was 2010. A VEI6 eruption at Marapi is lower-probability: its return period, which is the estimated average time between eruptions, is 750 years. Yet the stakes are high enough to merit taking the prospect seriously, says Lara Mani, a volcanologist at the University of Cambridge’s Centre for the Study of Existential Risk. And Marapi is one of several active volcanoes in the region. VEI4, VEI5 and VEI6 eruptions, says Mani, “can still really disrupt the strait. And the thing is, when a volcano starts, it doesn’t tell you when it’s going to stop.”
Let’s imagine that one of those active volcanoes – such as Semeru on Java, Indonesia – produces an eruption that would qualify as a VEI5 or VEI6. Magma bursts from the crater. Ash belches into the sky. Tremors shake local towns. If the wind is south-westerly, all air traffic in the Malacca Strait is grounded. The ash falls onto the strait itself. On the surface of the sea, rafts of pumice accumulate.
A large and relatively nearby earthquake would be a menace of similar scale. It could cause a tsunami to hit the strait, as the Boxing Day tsunami did in 2004. It would also cause turbidity currents – clouds of fast-moving, shaken-up sediment – that rip across the seabed. “That’s typically what severs cables,” Mani says. “In the Tonga eruption” – Hunga Tonga-Hunga Ha’apai’s VEI5 eruption in January 2022 – “it was turbidity currents that severed the cables, causing a regional internet blackout. The turbidity currents also bury those cables, making their recovery even harder.” (Read more about the scale and aftermath of this eruption from BBC News: “Tonga eruption: Atlantic seafloor felt Pacific volcano megablast”.
On the upside, these natural disasters would cause less disruption to global shipping than the Ever Given did, says Tristan Smith of University College London. Smith, a shipping expert at his university’s energy institute, says that ships’ machinery should be able to cope with ash and that a tsunami is more dangerous to people on land, where the wave breaks and is at its biggest, than on sea.
And presumably in the case of an eruption, an exclusion zone would be declared, forcing ships to take a different route. The rerouting of ships would have an effect on global trade, says Smith, but the system should ultimately be able to handle it. “If you have a ship that gets held up by three days, because it has to go the long way around Indonesia, all that ship needs to do is increase its speed by one or two knots and that delay is counteracted.”
There’d still be the matter of the grounded planes. The eruption of Eyjafjallajökull prompted a six-day airspace ban, resulting in disruption for millions of people. Worse, the severing of those cables would cause economic pandemonium. “Trillions of dollars are transported through those cables every single day,” says Mani, “and that basically props up our financial markets. Our submarine cables are vulnerable, and there have been accidents over the years.”
Mani highlights the breaking of several submarine internet cables by an earthquake near Taiwan in 2006, leaving a single cable connecting Hong Kong to the rest of the world. “It took 45 days to repair the other cables, and it was very lucky that one of them managed to survive. Imagine 45 days of nothing for Hong Kong and the broader region.”
It would have been catastrophic, she continues, not only for Hong Kong but for the rest of the world. Hong Kong, like Singapore, is a financial hub whose effective disappearance would cause worldwide economic havoc. “We just don’t have redundancy,” says Mani of the cables: if something goes wrong, there aren’t spares to pick up the slack. “And our satellites, in their current state, can only handle about 3% of global communication.”
So how can the strait be made less vulnerable? There is nothing we can do to stop earthquakes. The Intergovernmental Oceanographic Commission and Unesco have set up early-warning systems for events such as tsunamis, and there is an existing service (the World-Wide Navigational Warning Service) that warns maritime shipping of meteorological or geological disasters. The Japanese coast guard is the designated coordinator of the area that includes the Strait of Malacca.
As for volcanoes, it might one day be possible to avert eruptions by manipulating the magma beneath them, but we are many years from that being a realistic possibility. For now, we must get better not only at monitoring volcanoes – even a few hours’ notice of an eruption makes a big difference – but at spotting them. As Mani warns, Indonesia has “more volcanoes than you can shake a stick at, and many of them we” – the world’s volcanologists – “have never properly looked at.”
Elsewhere, the best preparation is diversification. More internet satellites would help. Local countries would also bolster their resilience by laying down new submarine cables that take a different route to the existing ones. China seems to be taking this approach to shipping. For years it has been trying to construct a canal across southern Thailand, obviating the need to go via the Strait of Malacca. The Thai Canal, as it is known, would reduce energy costs by providing a shortcut for crude oil transport, but it would also add significant resilience to Chinese shipping. Although the CCCP is thought to see this resilience in geopolitical terms, it might also turn out to be a useful insurance policy for global shipping. Finding ways of lessening their reliance on chokepoints like the Strait, says Ben Bland, director of Chatham House’s Asia-Pacific programme, is “definitely something that’s been on a lot of governments’ minds in Asia”.
The relevant government bodies of Indonesia, Malaysia and Singapore did not respond to BBC Future’s requests for comment, but we can assume that some amount of contingency planning will already be in place. Anyone who benefits from the Strait of Malacca – and if you are reading this, you are in that category – should hope that those plans turn out to be those that are never needed.