One of the three brothers, Hades, was always angry and jealous because of his brothers and how he was the only one who didn't live in the real world. He was tired of how he was the one who had to live in the underworld.
One day Hades got so angry he shot fire and magma out of his head. It went through a mountain and started the first volcano eruption.
Zeus and Poseidon were startled and went to the underworld to ask Hades if he knew anything. When the two brothers got there they had to face the vicious, three-headed dog Cerberus.
Zeus walked to Hades and asked why he was so upset. Hades said that he wanted a break from the dead souls and just wanted a tour of Mt. Olympus. So Zeus said that some day he would give him what he desired.
Poseidon made a magic chariot out of water so they could get out of the underworld. The three brothers went out of the underworld together going back to Mt. Olympus.
When they arrived at Mt. Olympus Zeus gave Hades a tour of his palace. Zeus told Hades that he could come whenever he wanted but, before he left he had to clean up the ashes from the volcano.