How Forest Fires Begin and Spread

• The temperature at which a substance ignites and begins to burn is called the flash point. The flash point of wood is 572 degrees. Once wood reaches its flash point, it creates a substance which reacts with oxygen to create a flame. The flame heats the wood, which then spreads the flame. This process explains how fires can spread even in very cold weather.
  
  

Lightning Strikes

• Lightning strikes are a very common cause of forest fires. The lightning strikes a tree, bringing the wood to its flash point. The tree begins to burn, with flames spreading to surrounding trees as well as to underbrush. Especially during drought conditions, forest fires can spread very rapidly after lightning strikes. Nearly 5.5 million acres of forest were burned by fires caused by lightning strikes in 2006.
  
  

Earthquakes

• Earthquakes can also cause fires in forests and in populated areas as well. The 1906 San Francisco earthquake touched off a number of fires over the entire area. Another earthquake that occurred in Tokyo in 1923 caused a fire which spread very rapidly because of overturned charcoal braziers. Earthquakes can cause fires by rupturing natural gas lines or, in areas of volcanic action, spreading volcanic material over the landscape.
  
  

Human Carelessness

• According to the Arbor Day Foundation, more than 83 percent of forest fires in 2006 were due to human activity, most of which was traced to carelessness. Campfires which have been improperly put out, carelessly tossed cigarette butts and other accidental human actions are a major cause of forest fires, many of which cause extensive damage and some of which have cost human lives.
  
  

Arson

• Arson is a very destructive source of forest fires. The reasons behind arson include attempted insurance fraud, pyromania (a mental disorder in which someone compulsively sets fires), revenge or even political motivations. According to a report issued by the International Institute for Counter-Terrorism, al-Qaeda has plans to use deliberately set forest fires in the United States, Europe and Australia as part of its terrorist arsenal.