What Causes Wildfires

A wildfire is an uncontrollable and rapidly spreading fire, occurring on wildland, rangeland or brushland. Also referred to as wildland fires or vegetation fires, these fires travel at an average speed of 15 miles per hour destroying everything on their track. On an average, about 1.2 million acres of woodlands in the United States, burn every year due to wildfires. Following are the major factors that lead to a wildfire.

Most of the wildfires are caused by human interference and roughly amount to more than 90% when they invade the forest area by cutting down acres of land. Debris burning and arson (burning to destroy property) are examples of other human activities that often result in violent infernos.

It is a common practice of farming that refers to cutting and burning of woodlands and vegetation for clearing the land. Quite often, the slash-and-burn practice results in catastrophic wildfires.

Wildfires caused due to lightning occur at a frequency of three to five per year. Since lightning is usually associated with rain, such fires do not spread over large areas.

Extreme hot temperatures lead to drying up of the vegetation of that particular area and can aggravate a wildfire by fueling it all the more. Moreover, an already ignited fire can spread over large distances with wind as its medium.

Sometimes, volcanoes create a favorable condition for ignition of wildfires in the surrounding areas. They are also caused due to pyroclastic clouds (those containing rocks or ash from volcanic eruption), generated from active volcanoes.

Underground coal fires are the slow and flameless forms of combustion, below the earth's surface. Such fires continue to burn for many years, resulting in the release of toxic fumes and destruction of vegetation and human property.

They are controlled fires meant to eliminate the elements which can aggravate a wildfire or a forest fire. Often, they are a part of wildland management. Sometimes, these prescribed fires are also not channelized properly and they lead to catastrophic infernos.

When all these factors act at once, they are enough to ignite a spark in the potential fuel materials. The hot and dry weather, often a drought, converts healthy green vegetation into inflammable fuel. When a spark is ignited because of lightning, cigarettes, or arson, the winds help in spreading the fire over acres of land. The warm or hot weather leads to burning of fuels until their exhaustion.

The three essential components for a wildfire to form are oxygen, fuel and a heat source. These three elements, which the firefighters refer to as the "fire triangle", are interdependent and play a significant role in spreading the fire over a large area, whether the cause is man-made or natural.

Heat Source: As the name suggests, it is something that helps ignite a fire with the help of the available fuel. The Sun, campfires, and even something as small as a cigarette can play the role of a heat source.

Wildfires are more prevalent in summer and autumn because of the weather patterns prevailing during these seasons. They are also common during droughts, when the fallen branches and leaves become dry and flammable.

However, the overall spread of these fires depends on weather, type of vegetation and the geography and topography of the area. Under the influence of strong winds, wildfires can spread to more than 40 miles a day, which is about 1000 acres per hour.

In order to extinguish wildfires, firefighters use Pulaski (combination of an ax and hoe) to dig a fire line. While constructing a fire line, the mineral soil is exposed (by removing the surface litter and organic matter), so as to stop the spread of wildfires. In case of huge wildfires, helicopters and airplanes are used for spraying water and fire-retardant chemicals to extinguish the fire.