I was going to write something up about Mount St. Helens, which erupted 30 years ago today. But then The Big Picture went and did an incredible retrospective of it, so I'll just send you there. Here's a taste:
If you've ever wondered what my nightmares are like, you're looking at one. I'll add that a few years ago, when I still lived in California, I flew up to Seattle for a meeting. I literally gasped out loud when I saw the volcano out my window. I stared at it for as long as it was visible. The whole story was laid out clearly for anyone to read it: the side of the caldera was collapsed, and I could see the long run out from the lahar, the mudslide that followed the eruption. Even nearly three decades later the devastation was incredible. Over 3 cubic kilometers (0.67 cubic miles) of rock and ash blew out of the volcano that day. You can read about the details of the event on the USGS site and on their 30th anniversary page. It's a hair-raising story. [Edited to add: This NASA series of pictures is also way cool.] And by the way? The volcano is still active. Have a nice day. Image credit: USGS.