By Staff
You probably heard that the wildfires that have been so stubbornly burning down in Georgia and Florida finally got a substantial dousing of rain. Everyone thought that would be the long awaited end, but not so.
Though the rains allowed most of the obvious flames to be curtailed a lot of the area is now burning underground – the dreaded muck fire. It seems inconceivable that the wet, black, mucky soil found under many marshy areas can burn. Until I became a wildland firefighter and experienced it first hand I'd have never believed it.
Most soil is mineral soil, meaning it is just finely ground rock; your typical sand. This can't burn no matter what. Muck soil, however, is not sand, but decomposed vegetation. Over the millennia everything in a marsh from cattails and lily pads to shrubs and leaves just keeps sinking to the bottom and rotting. After a few thousand years a layer of this decomposed vegetation forms that can be anywhere from a few inches to many feet thick.
The older the marsh the thicker the layer of muck soil. This soil is basically carbon, in the same category as burnable stuff such as wood and coal. Some marshes also have an underground layer of peat moss, which is much less decomposed and burns even better yet.
"Yea," you say, "but it's wet so how can it burn?" Muck fires usually occur in swamps that are fairly dry to begin with, from draining, natural succession or long drought. Your typical, above ground wildfire dries out the moisture at the very surface, allowing this now dry muck to smolder like charcoal.
As it seemingly benignly smolders away it continues to dry the muck underneath out. Like a sneaky creature of the Black Lagoon it inches its way underground. As days and weeks go by it works deeper and spreads out, often completely hidden by a thin layer of more moist, unburned top soil. This is dangerous as fire fighters can break through this cover and find themselves wading in a red hot bed of coals.
Given the right circumstances and enough time these underground fires can grow to immense proportions yet be completely unseen. Then, sometime in the future, it may find a route back to the surface and there goes another wildfire. These underground muck fires can burn for days, weeks, months or even years.
A couple of years ago I worked a muck fire up by Grand Rapids. The landowner said it had started in early spring. It didn't seem to be going anywhere or doing anything so he didn't report it.
However, a smoldering muck fire gives off a unique, nasty odor and as the weeks went by the stench got worse and worse. Finally someone reported it and we (DNR firefighters) were called in. It had been going about two months and finger like tendrils of fire had sprawled underground throughout the entire 10-acre marsh.
That same year we were sent to a similar muck fire in Berrien County. It had been smoldering most of the summer. We started work on it in early October and despite some sporadic snow falls it was still going at the end of December. If finally went out on its own sometime that winter under a heavy layer of snow.
It's the labor involved in putting out a muck fire that gives fire fighters nightmares. You can't get conveniences like fire trucks, bulldozers and such out into the marsh. They would just end up sinking into a gooey grave. You have to dig up every foot of the fire by hand with shovels and axes so you can get at it with water. You have to chop and dig out every bush and stump for the roots provide the fire a path to the surface. You have to drag hundreds of yards of heavy hose around in the marsh. A fire hose has an amazing will of its own bent on tangling around everything that it possibly can. Yea, those firefighters were just getting loosened up working the newsworthy flames. Now the real sweating begins. Carpe diem.