Image: Ed Austin/Herb Jones
In fact, a mega-eruption of this kind is worryingly overdue, according to volcanologists. The caldera should, in theory, dramatically blow its top every 600,000 years, and the last time it erupted was 640,000 years in the past. Ominously, there are signs that something is bubbling, too: scientists discovered that sections of the national park rose some 27 inches during the 20th century, while magma levels beneath the surface have been climbing alarmingly since 2004. And if, or indeed when, the supervolcano blows, it could devastate a 2,000-mile stretch of land between Oklahoma and Canada, killing thousands and bringing the American economy to its knees.
Image: Luc Viatour / www.Lucnix.be
2. Cumbre Vieja – Canary Islands, Spain
When La Palma’s Cumbre Vieja volcanic ridge next erupts – probably within 150 years – a 15-mile-long chunk of its westerly flank may collapse into the Atlantic. The impact of such an event would result in a “mega-tsunami” – a series of huge waves that would engulf the Canary Islands before spreading east towards Africa, west in the direction of North and South America, and north headed for Spain and the U.K. If this happens, the waves are expected to travel as fast as 500 mph, and those hitting Morocco could be as high as 330 feet. However, Florida, the Caribbean and Brazil would likely endure the brunt of the devastation, with waves up to 164 feet high pushing water up some five miles beyond the shoreline, wrecking everything in its wake.