Layout

‘Volcanic eruptions are like cats’: the La Palma volcano explained

On 19 September, after 50 years of magmatic quiescence, the Cumbre Vieja volcano on the Spanish island of La Palma roared back to life. Ash speckled the sky, and molten rock cooking at 1,075C (1,967F) oozed from several fresh fissures and cascaded down the volcano’s western flanks in the form of hadean rivers, ploughing through houses and farms with insouciance. Fortunately, thanks to the work of local scientists and emergency services, thousands of people were evacuated ahead of time, and no deaths have yet been reported.

So, what happens next? What new threats will emerge from the volcano? How long will this go on for? And why would anyone want to live in the shadow of such a menacing volcano in the first place?

How long is this eruption going to go on for?

That’s incredibly difficult to say. It could suddenly stop in the next few days, or it could go on for months. The average length of an eruption on La Palma in the Canary Islands is a month, but volcanic eruptions are like cats: they all possess their own distinctive personalities, and the duration of their paroxysmal moods can vary wildly.

What are its hazards?

The primary hazard is the relentless flow of lava – it has already bulldozed through hundreds of homes on the southwestern corner of the island, and it will continue to do so as it crawls its way towards the coast. The ash, too, is a problem: it’s not great to breathe in, especially if you have a pre-existing respiratory condition; it also creates visibility problems, burns out electric circuits, kills off car engines, pollutes waterways and smothers crops. A more insidious danger comes courtesy of the density of volcanic ash: the weight of accumulated ash on rooftops can cause them to collapse.

The eruption has become more explosive as of late. I’ve heard that this could cause a landslide and, in turn, a dangerous tsunami. Should I head for higher ground?

Volcanologists are concerned about the flanks of unstable volcanoes tumbling into the sea, which can and have triggered destructive tsunamis. A speculative paper from 2001, which formed the basis of an uncritical and sensationalist documentary, suggested the catastrophic collapse of the Cumbre Vieja volcano could cause a tsunami that would drown America’s eastern seaboard in waves up to 25 metres (82ft) high.

Click to continue reading