It looks like a cross between something seen on "V" and a beret, but actually this circular cloud pictured above is just a harmless lenticular cloud. The photo was taken by Annie Roehr over the weekend. (Larger resolution version here.) The cloud might look like a hat, but it's actually several thin layers of clouds stacked upon each other like a stack of pancakes.
Lenticular clouds can really put on some shows, especially over Mt. Rainier. (I'm still getting e-mails and Facebook hellos over that article, which has been running amok on the Internet for nearly two years now.)
How about a cloud that's not so harmless? Have you seen these photos of the incredible lightning photos from the erupting E...y...ja...z?..q?..., um, volcano in Iceland?
There's an even better one at the Astronomy Picture of the Day website
And here is some video of a volcano erupting in Hawaii in 2008:
While we're on the subject of volcanoes, a lot of you have had questions on whether this eruption could have any temporary impact on global or regional climate.
The 1991 Mt. Pinatubo eruption in the Philippines is widely credited with about a three-year drop in average Northern Hemisphere temperature of about a degree, as the sulfur dioxide from the volcano got well into the stratosphere, where it spread around the globe, and turned into a sulfate haze that restricts sunlight a bit.
Check out this entry in UW Prof. Cliff Mass' blog. He goes into great detail why he thinks this eruption won't have any effect on our climate.