Anatomy of a wildfire: How fuel sources, weather and topography influence wildfire behavior

On the surface, wildfires seem simple. There’s a spark, a few small twigs flare up, and it spreads throughout a forest landscape until it runs its course or is doused by firefighters. But how exactly do wildfires happen, and what factors determine whether a fire will stay calm or burst into an unpredictable and uncontrollable force of nature?