Axel faces the challenge to overcome his fear and survive. Keeping the events that recently occurred, explore and comment on the theme of perseverance and survival.

While much of Verne's depicted journey is awe-inspiring yet fairly safe, at other times it is incredibly dangerous and requires more of the travelers than note-taking and walking. In fact, Nature is at her most primitive beneath the Earth, and these human beings must necessarily adapt themselves to her. Water is not a given, tempestuous storms rage and destroy, fearsome beasts emerge, the wind takes the expedition off course, and the dark is heavy and lonely. There are several points along the journey at which Axel and his companions actually come close to perishing; Axel's finding himself lost and alone is one of the more terrifying episodes. Overall, this journey requires of its participants that they be willing to sacrifice almost everything—perhaps even their lives—to complete it.