Like all fires, a wildfire (also known as a forest fire, brushfire or bushfire) requires three ingredients: oxygen, heat and fuel. A wildfire is large, uncontrolled and potentially destructive and spreads quickly and may change direction or jump across gaps. Wildfires can affect rural and urban areas, and can start in just seconds, sparked by a range of natural causes (for example, lightning) or human carelessness (such as a discarded cigarette). The spread of wildfires depends on the topography, the fuel available and the weather. Dry vegetation and abundant or dead wood that has not been cleared are all sources of fuel. A small fire can become a rapidly spreading inferno in a matter of minutes – particularly if it is windy.