What causes a Bushfire?

A Bushfire can be caused by:

Lightning strikes

Extreme heat (at least 45 degrees)

Dry winds

People droping their cigarette butts on the  grass

Sparks, from a campfire

Earthquakes

Spreads:
When a Bushfire starts it small but then spreads with the embers and dry wind making it bigger.
 
Embers are hot, broken off, minature pieces of wood or coal that rise to the top of the flame by thrusts of hot air, then float in the air and if it lands on top of a leaf, stick or bushy area it usually starts another fire creating a bigger and stronger fire.

Facts:
Lightning strikes are the most common and natural for a bushfire to start in Australia.

The people that start bushfires on purpose are called arsonists.