Blue Collar Scientist

When the intense heat of a forest fire or volcano warms the humid air above, the air rises to a point of stability, generally within a humid layer of atmosphere. The phenomenon creates what is known as a pyrocumulus cloud¹.

When the cloud gets so big, and so turbulent, that it exhibits electrical activity, it graduates to pyrocumulonimbus status.

That’s what’s happening at Chaitén, the volcano in Chile that has been erupting recently. And some photographers are taking some spectacular photos of the phenomenon, like this one picked up by National Geographic, and this one by an uncredited photographer.

The last decent-sized pyrocumulus that I saw was while I was hiking on the Iceberg Notch trail in Glacier National Park in northern Montana. A small forest fire on the nearby Blackfeet Indian Reservation created a pyrocumulus, the turbulence and winds of which quickly whipped the fire into a huge conflagration. After my hike was over, it graduated to pyrocumulonimbus status, giving us a nice electrical display as we tried to get back to our rental cabin on a road that went right through the firefighters’ central command and even a small corner of the fire itself. Quite exciting.

1. Nuclear detonations, and sometimes industrial activities, can also create these clouds. [↩]

Tags: Chaitén, cloud, pyrocumulonimbus, pyrocumulus, storm

This entry was posted on Friday, May 9th, 2008 at 12:51 pm and is filed under weather. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.