In Battle of the Morannon, when the ring is destroyed in Mount doom, the Dark Tower collapses. Then, The Eye of Sauron implodes and creates a shock wave which causes an earthquake that shatters the ground and ground starts to collapse.
So in this scene, How come the ground did not collapse under Aragorn's army and the fellowship? Is it because of the presence of Gandalf? or does he use a special spell?
Can it be even related with Eru (Ilúvatar) ?
You can see the scene in this video as well: (at 2m55s)