MICHAEL BLEBY: Gonna blow? Japan updates response plan for a Mount Fuji eruption

You know the iconic image of the bullet train speeding past Mount Fuji? Well, that train wouldn’t run if Japan’s tallest — and volcanic — mountain erupted.

Nor, come to think of it, would cars or planes. A huge eruption of Mount Fuji would rain down so much ash that it would take only three hours to bring the network of trains and highways in Tokyo — just 100km away — to a halt.

Last week Japan updated its disaster response plans for a Fuji eruption, setting out how the 800,000 people living in the vicinity of the mountain would evacuate (by foot as far as possible, to avoid the roads clogging up with cars) and how they would survive the immediate aftermath (by spending a week inside to avoid the respiratory-system risks of ash-filled air).

But the prospect of the 3,776m-high volcano erupting in a big way, which it hasn’t done since 1707, more than 300 years ago, is not just a problem for the people living in the three prefectures (provinces) at the foot of the mountain. It’s a problem for the Greater Tokyo Metropolitan region of about 30-million people. And it’s a problem for the rest of the world.

Lava flows are scary, but ash is the bigger problem. While it would take about 24 hours for lava to flow from an erupting Fuji to the shinkansen (bullet train) line, ash would almost certainly shut down the world-pioneering fast train far earlier.

Just half a millimetre of ash would force trains to stop running. One millimetre of the stuff on the roads would force cars to drive at a maximum speed of 30kph. Five millimetres would cut their speed to 10kph. And at 10cm the roads would become impassable.

Back in 1707 Fuji’s eruption covered Tokyo in a thick layer of ash, burying farmland. Many people starved. In 2014 the country suffered its worst volcanic disaster in more than 90 years when the 3,067m-high Mount Ontake, 200km west of Tokyo, exploded without warning, killing 63 hikers.

Of course, Japan is just one country where volcanoes pose a serious risk. Other countries flagged in a 2009 academic paper as having the highest level of volcanic hazard or vulnerability were the US, Indonesia, Ecuador, Papua New Guinea, Italy, New Zealand, Philippines, Mexico and the UK.

They can happen in many places, and the fallout isn’t just local. The 2010 eruption of Iceland’s Eyjafjallajökull volcano disrupted global supply chains, including the flow of what was then estimated at 10,000 tonnes of airfreight transported daily between Asia and Europe. Carmaker Nissan suspended production at two plants due to a lack of parts imported from Ireland.

The economic miracle of middle-class growth in Asia and the surge in e-commerce guarantees that the cost of any disruption to air travel and transport in the region will be far higher than it was back then.

The problem for planes is that ash in a jet engine can cause it to stall. In June 1982 flight BA009, en route from Kuala Lumpur to Perth, flew into a cloud of dust and ash from the eruption of Mount Galunggung on Indonesia’s island of Java, and all four engines failed.

“Ladies and gentlemen, this is your captain speaking,” Captain Eric Moody told his passengers. “We have a small problem. All four engines have stopped. We are doing our damnedest to get them under control. I trust you are not in too much distress?” Moody and colleagues glided the 747-200 out of the cloud and were able to restart three engines, landing safely at Jakarta. 

The Covid-19 pandemic laid bare the frailty of global supply chains. There has been the odd tragicomic reminder along the way — remember the Ever Given mega-container ship and its $9.6bn-a-day blockage of goods in the Suez Canal in 2021? Disruptions from a volcanic eruption could seriously hamper transport and freight in a region of the world that is a big cellphone and semiconductor producer.

So how likely is it? No-one really knows. In 2014 French and Japanese scientists said seismic waves from the Great East Japan earthquake of March 2011, which triggered the catastrophic tsunami that caused the Fukushima nuclear power plant disaster, had damaged the earth’s crust and built up pressure in the volcanic region under Mount Fuji 400km away. But the Japan Meteorological Agency played down any link between Fuji erupting and earthquakes after a 4.8 magnitude quake at the mountain.

It’s one of those too-scary-to-contemplate scenarios. People practise how to cope with it, desperately hoping they never have to.

• Bleby is a senior reporter with The Australian Financial Review, based in Melbourne.