"HM?"
The black dragon noticed the changes on the ground. A few moments later, the dragon felt very heavy, and the earth suddenly collapsed.
The Meteor that the fox cast had intended to deplete the dragon's critical mana, forcing it to cancel its flying spells and descend, allowing it to set itself on her trap.
The dragon is a bit sluggish due to the toll of its World Magic spell, so it didn't have enough time to use its wings and helplessly fell into the deep chasm in the end.
The gorge that the dragon fell off was quite large enough to fit the dragon whole. It was round and measured to be around two hundred meters wide and at least three hundred meters deep.
What the silver fox did was excavate the underground using the Earth Magic Level 10 Sinkhole. Actually, using the Sinkhole over that volume of earth takes time to sink the ground, but she has a way to hasten the process so that it occurs almost instantly.