No Doubt, Redoubt

Unless you're living under a rock, you probably already know that Mount Redoubt, a stratovolcano located 103 miles north of Anchorage, Alaska, started to erupt on Sunday. So far, it's belched out a couple of big ash clouds: a 50,000 foot high one during the first set of eruptions on Sunday night, and a second cloud just as big late on Monday.

So, what happens next? A 9 mile tall cloud of razor-sharp bits of powdered rock doesn't just vanish into the atmosphere. The heavier particles are already coating cars and rooftops in towns near Anchorage, as you can see in this photo showing ashfall from NASA’s Earth Observatory site. But the lighter bits stay in the air longer, and it’s those bits that could be problematic.

For starters, they’re a health hazard. Inhaling glass isn’t good for man or beast. And because volcanic dust is both corrosive and conductive, it can make machinery seize up. Annoying when the machinery is on the ground, but potentially disastrous when it’s in the air, as the passengers of KLM flight 867 to Anchorage found out when Redoubt erupted a decade ago. Ash stopped all their plane’s engines as they came in for a landing, and they fell 2 miles before their pilots (thankfully) got them restarted. Which may be why your flight is late. And one of the reasons these volcanoes are so closely monitored. There are a lot of international flights over Alaska.