Dust!

British airports will be closed today because of the huge cloud of volcanic ash drifting over from Iceland. Despite throwing tons of bright orange liquid rock into the air and making a lot of noise, volcanic activity has its downside. Ask the crispy-coated people of Pompeii. They hated volcanoes.

When Krakatoa blew its top in 1883, a little to the WEST of Java, the explosion was four times more powerful than the biggest ever nuclear bomb detonation. The bang was heard over 3,000 miles away and around 21 cubic kilometres of rock, ash and dust was chucked up into the sky. All this stuff floats around for ages, making a mess, ruining stuff and making the weather go all funny. And it killed over 36,000 people. Also very bad.

But there have been eruptions far more powerful than Krakatoa. Whether they contributed to the demise of the dinosaurs or not, at the time of the extinction event at the end of the Cretaceous around 65 million years ago the Deccan Traps in India were spewing out ash and gas that would have been spread across a large part of the globe and affected the climate pretty dramatically. The huge meteorite landing in Yucatan at the same time sent up enough junk to make the sky all black and kill nearly everything. Impact Winter, it's called. So - combining the two makes for an unhappy time for the dinosaurs, known to be fond of an outdoor lifestyle.

Another mass extinction, at the end of the Permian about 250 million years ago, can be landed squarely at the feet of Vulcan, the cantankerous god of fire and volcanoes. The Siberian Traps were thousands of times more powerful even than Krakatoa. Again - nearly everything died. Statistically, we're most likely overdue another super-eruption somewhere. But statistically, we're most likely due for another enormous earthquake and meteorite impact. Stock up on the beans and bottled water and check for loose roof tiles while you still can.

The bad news for this guy is that the last time Eyjafjallajokull erupted, 200 years ago, it went on for two years. Not only that, but there is another, larger volcano nearby which is very often triggered by it. This could take a little while.