Massive duststorms... in Alaska?

When you think of a massive dust storm, if you're like me, you probably don't think about South-East Alaska. I'm more likely to think of Saudi Arabia or Kuwait than Alaska's Banana Belt. And yet, there it is:

That's a photo from NASA. So, what on earth are those massive plumes streaming off the coast from? Give it a guess, and then check out Phil Plait's answer. :) NASA does an awful lot of Earth observing, and generates a whole bunch of critical data. That's not bad for an agency who's entire budget costs us much less than one percent of the federal budget.