Question

Why don't trees spontaneously catch on fire and burn all the time? Why don't fires stop immediately as soon as they start? Develop a model for what has to happen for a large fire to occur.

Answer 1

Both of these phenomena is due to the ignition temperature.

Step-by-step explanation:

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.