The Adventures of Captain Hatteras: The Desert of Ice - Jules Verne

Why would the Captain jump into a volcano crater? And will he make it back out alive?"The Desert of Ice" is the second part of Jules Verne's novel "The Adventures of Captain Hatteras" from 1864. Captain Hatteras and his crew who have survived the long winter on island "New America" continue their expedition to the North Pole. They discover an island with an active volcano and it turns out that the exact location of the pole is in the crater. Is this the end to the long, difficult and dangerous expedition? If nobody survives how will the rest of the world learn about it? Is it possible that the Captain survives, and is the information he gained more important and valuable than his own health and well being?