In Disney’s 1998 animated film Mulan, Mulan fires a cannon to trigger the avalanche.
During the battle in the mountain pass, Mulan realizes that the surrounding snow can become a weapon. She takes aim at the mountain rather than directly at the Hun army and fires a cannon into the slope. The resulting avalanche overwhelms the invading force and gives the imperial troops a chance to survive.
The scene is sometimes described loosely as Mulan using an explosion or a cannonball, but the specific weapon is a cannon from the army’s artillery. The avalanche is not caused by a catapult, crossbow, or firework.
Mulan’s decision demonstrates the strategic thinking that distinguishes her from the other recruits. She wins time by observing the landscape and using it creatively. The plan is dangerous, however, and Mulan is nearly swept away before Shang rescues her.