Puuvaaran

Puuvaaran is a term used in Finnish to describe a type of forest fire that originates from the decomposition of organic matter within peat or humus layers in the soil, rather than directly from burning trees or surface vegetation. These fires are often referred to as "ground fires" or "smoldering fires" in English.

Puuvaaran fires are characterized by their slow spread and tendency to burn underground for extended periods, sometimes weeks or even months, especially during dry conditions. The fuel for these fires is the deep layer of organic material accumulated over time in bogs, mires, and older forests. Because the flames are often hidden beneath the surface, these fires can be difficult to detect and extinguish, posing a significant challenge for firefighters.

The conditions that favor puuvaaran include prolonged periods of drought, low humidity, and the presence of dry, combustible organic matter in the soil. Once ignited, the smoldering process can generate substantial amounts of smoke, which can travel long distances and impact air quality over wide areas. Extinguishing puuvaaran fires typically requires extensive excavation to expose the burning material and saturate it with water, or sometimes controlled backburning to remove fuel ahead of the fire. These fires can cause significant damage to forest ecosystems and soil structure.