How do wildfires start

Human-caused wildfires There are numerous ways human activity can start wildfires, either accidentally or intentionally. Wildfire investigations Wildfire investigations often take time to complete and can be very complex. Copy Cancel. Did you find what you were looking for? Thank you for your response. Help us improve gov.

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These three factors include fuel , weather and topography. Depending on these factors, a fire can quickly fizzle or turn into a raging blaze that scorches thousands of acres. Fuel can include everything from trees, underbrush and dry grassy fields to homes. The amount of flammable material that surrounds a fire is referred to as the fuel load.

Fuel load is measured by the amount of available fuel per unit area, usually tons per acre. A small fuel load will cause a fire to burn and spread slowly, with a low intensity. If there is a lot of fuel, the fire will burn more intensely, causing it to spread faster. The faster it heats up the material around it, the faster those materials can ignite. The dryness of the fuel can also affect the behavior of the fire. When the fuel is very dry, it is consumed much faster and creates a fire that is much more difficult to contain.

Small fuel materials, also called flashy fuels , such as dry grass , pine needles, dry leaves, twigs and other dead brush, burn faster than large logs or stumps this is why you start a fire with kindling rather than logs. On a chemical level, different fuel materials take longer to ignite than others. But in a wildfire, where most of the fuel is made of the same sort of material, the main variable in ignition time is the ratio of the fuel's total surface area to its volume.

Since a twig's surface area is not much larger than its volume, it ignites quickly. By comparison, a tree's surface area is much smaller than its volume, so it needs more time to heat up before it ignites.

As the fire progresses, it dries out the material just beyond it -- heat and smoke approaching potential fuel causes the fuel's moisture to evaporate. This makes the fuel easier to ignite when the fire finally reaches it.

Fuels that are somewhat spaced out will also dry out faster than fuels that are packed tightly together, because more oxygen is available to the thinned-out fuel. More tightly-packed fuels also retain more moisture, which absorbs the fire's heat. Drought leads to extremely favorable conditions for wildfires, and winds aid a wildfire's progress -- weather can spur the fire to move faster and engulf more land.

It can also make the job of fighting the fire even more difficult. There are three weather ingredients that can affect wildfires:. As mentioned before, temperature affects the sparking of wildfires, because heat is one of the three pillars of the fire triangle. The sticks, trees and underbrush on the ground receive radiant heat from the sun, which heats and dries potential fuels. Warmer temperatures allow for fuels to ignite and burn faster, adding to the rate at which a wildfire spreads.

For this reason, wildfires tend to rage in the afternoon, when temperatures are at their hottest. Wind probably has the biggest impact on a wildfire's behavior. It also the most unpredictable factor. Winds supply the fire with additional oxygen, further dry potential fuel and push the fire across the land at a faster rate. Terry Clark, senior scientist at the National Center for Atmospheric Research, has developed a computer model that shows how winds move on a small scale.

Since , he's been converting that model to include wildfire characteristics, such as fuel and heat exchange between fires and the atmosphere.

Smoke from a fire can cause poor visibility for the helicopters and airplanes that are used to fight fires. Thankfully, GOES satellites are always up there keeping an eye on things to try and help us stay safe! Weather Forecasting. The Short Answer:.