30 years ago, Mount St. Helens erupted with catastrophic results, killing 57 people. The event was caught on camera, and the famous images are awe-inspiring...mother nature at her most violent:
There are a number of excellent features around the web commemorating the disaster. Boston.com's "The Big Picture" has a wonderful photo-essay showing the effects of the volcano, both then and now (I didn't realize that 1000s of fallen trees still float in nearby Spirit Lake). National Geographic - who documented the event in their magazine - have an article on their website as well as a heart-breaking video story. The Oregonian has a photo story on Harry R. Truman, the folk hero of Mount St. Helens. And for a really detailed look at the topic, make sure you check out the Nova documentary (sadly, complete video is restricted for non-US viewers).
Eyjafjallajökull has recently put us on notice that we're fairly insignificant compared to the natural processes of our planet, but Mount St. Helens walked right up to us and slapped us in the face.