What Are Ash Pits? The Wildfire Hazard Most People Don’t Know About

They say you learn something new every day, and I just learned about ash pits and underground fires. How does a fire burn underground? Also, what is an ash pit? I didn't even know what to watch out for until I saw this.

I've been following the U.S. Forest Service - Superior National Forest's post since the BWCA wildfires began. It's believed they were started by dry conditions and lightning strikes. The area has seen less than half the normal amount of rain, which has turned a lot of the forest into a tinderbox.

Underground fires are possible in Northern Minnesota and Canada because of the way the land was shaped by glaciers millions of years ago. The glaciers scraped the land all the way down to bedrock. Over time, plants grew and died on the bedrock, creating the organic material called duff.

This material isn't tightly packed and has air pockets. Roots form, extend, and interconnect underground. When a tree is hit by lightning, the tree can catch fire, and it can spread into the roots. Even if the tree appears to no longer be burning, the fire can be slowly smoldering a few feet underground. This can spread to other trees and vegetation where there is more oxygen, and it can ignite another fire above ground, or continue burning underground.

Some of these fires could be just smoldering for days, weeks, or even months.

Sometimes, these underground fires can burn large areas of roots, which creates an ash pit. Firefighters are aware of the dangers of these ash pits, because people can actually fall in them and be burned. Seriously, how did I just learn about this now?

To put these fires out, firefighters dig down as far as the mineral dirt and douse the fire with lots of water.

Read More: How To Protect Your Lungs From Wildfire Smoke