underground coal fires and even just throwing a lighted cigarette can ignite wildfires. In areas where there are many dried up leaves and trees, throwing a lighted cigarettes might just cause these to burn out of control. Many are started by arson, such as slash-and-burn, which is considered the least expensive way to clear land for future use such as farming crops. Flammable grasses caused by overlogging also contribute to the ease of igniting wildfires. Lightning, volcanic eruptions and such, which produces heat and even light, can cause the forests to catch fire and spread all over.