Why does Antigone die within a few hours of being put in the cave?
In Antigone, Creon decided that Antigone, as punishment for burying her brother, Polynices, would be entombed alive. Creon ordered that Antigone be sealed in a cave with food, as he claimed was the custom. After sentencing Antigone, Creon told the guards:
You know your orders: take her to the vault and leave her alone there. And if she lives or dies, that’s her affair, not ours: our hands are clean.
His intention was to remove Antigone from Theban society and condemn her to certain death by sealing her in a cave with a limited amount of food; however, he believed that by not ordering Antigone’s direct execution, he would avoid a stain on the reputation of Thebes, and, by extension, on himself as king of Thebes.
Antigone, once entombed alive, took action to decide her own fate. The messenger, recounting the events at Antigone’s place of imprisonment, told the Chorus and Euridice, Creon’s wife, that Antigone had hung herself in the cave. Instead of trying to subsist for however long possible on the limited amount of food provided to her, she took her own life shortly after being sealed in the cave.