In 2009, American geologist Adrian Helmsley visits astrophysicist Satnam Tsurutani in India and learns that neutrinos from a massive solar flare are causing the temperature of the Earth's core to rapidly increase. Arriving at a party in Washington, D.C, Helmsley presents his information to White House Chief of Staff Carl Anheuser, who takes him to meet the President.
It has been four years since the events of the first movie. Seventeen-year-old Sean Anderson (Josh Hutcherson) is caught by the police after a brief chase on his dirtbike which ended with him driving into a swimming pool while trying to evade them. Minutes later, his stepfather Hank (Dwayne Johnson) arrives where a police officer (Stephen Caudill) who is friends with Hank tells him that Sean had broken into a remote satellite research center. The police officer also tells Hank that he has talked Mr. and Mrs. McGillicutty (the owners of the swimming pool) out of pressing charges. Hank takes Sean home where his mother Elizabeth (Kristin Davis) is not pleased with his actions or the fact that he and Hank don't get along well.
Dr. Harry Dalton (Pierce Brosnan), a volcanologist of the United States Geological Survey, and his partner Marianne (Walker Brandt), are studying volcanic activity in Colombia when the volcano erupts. Marianne is killed by a piece of falling debris, leaving Harry remorseful about her death, believing it could have been prevented by evacuating sooner.
An earthquake strikes the city of Los Angeles. Mike Roark (Tommy Lee Jones), the head of the city's Office of Emergency Management, insists on coming to work to help out with the crisis, even though he has taken a vacation with his daughter Kelly (Gaby Hoffmann). His associate Emmit Reese (Don Cheadle) notes the quake caused no major damage, but seven utility workers are later burned to death in a storm drain, one escaped and survived but was severely burned on one side of his face at MacArthur Park. As a precaution, Roark tries to halt the subway lines which run parallel to where the deaths took place, but Los Angeles MTA Chairman Stan Olber (John Carroll Lynch) declines, feeling there is no threat to the trains. Against regulations, Roark and a colleague Gator Harris (Michael Rispoli) venture down the storm sewer in the park to investigate. They are nearly burned to death when hot gases suddenly spew out of a crack in the concrete lining and flood the tunnel. Geologist Dr. Amy Barnes (Anne Heche) believes a volcano may be rapidly forming beneath the city with magma flowing underground (similar to the formation of the Mexican volcano Parícutin which emerged and grew tremendously in just one week) but cannot come up with enough evidence for Roark to take action.
An American NASA spacecraft is hijacked from orbit by another, unidentified spacecraft. The U.S. suspect it to be the Soviets, but the British suspect Japanese involvement since the spacecraft landed in the Sea of Japan. To investigate, MI6 operative James Bond—agent 007—is sent to Tokyo after faking his own death in Hong Kong and being buried at sea from HMS Tenby (F65).
In the opening scene, Max Anderson (Jean-Michel Paré) is being pursued by a Giganotosaurus. Max then comes across a fissure vent. When he tries to jump across, he falls while calling out the name of his brother. Ten years later, Max's brother volcanologist Trevor Anderson (Brendan Fraser) is visited by Max's son/Trevor's 13-year-old nephew Sean Anderson (Josh Hutcherson). In a box of items that belonged to Max is a book, Journey to the Center of the Earth by Jules Verne. Notes written by Max are found inside the book.
Max (Cayden Boyd) is a lonely child in the suburbs of Austin who creates an imaginary world named Planet Drool, where all of his imagination and dreams come to life. He creates two characters; Sharkboy (Taylor Lautner), a young boy who was raised by sharks after losing his father at sea, and Lavagirl (Taylor Dooley), who can produce fire and lava, but has trouble touching objects without setting them alight. The two left Max to guard Planet Drool. In real life, Max's parents (David Arquette and Kristin Davis) have little time for him and their marriage seems to be on the rocks, and he is bullied by fellow schoolmate Linus (Jacob Davich). However, he does receive friendship from Marissa (Sasha Pieterse), the daughter of his teacher Mr. Electricidad (George Lopez, whose name is Spanish for "electricity"). Linus steals Max's Dream Journal (where all of his ideas are kept) and vandalizes it. The next day, a tornado rages outside the school, and moments later, Sharkboy and Lavagirl appear and ask Max to come with them to Planet Drool. They reach Planet Drool via a shark-like spacecraft, where Max learns that the dreamworld is turning bad, courtesy of Mr. Electric (also portrayed by George Lopez), originally the dreamworld's electrician but now corrupted.
Submersible pilot Toshio Onodera wakes up pinned inside his car in Numazu after an earthquake wreaks havoc in the city and nearby Suruga Bay. As aftershock triggers an explosion, a rescue helicopter led by Reiko Abe saves him and a young girl named Misaki.
Joe Banks (Tom Hanks) is a downtrodden everyman from Staten Island, working a clerical job in a dreary factory for an unpleasant, demanding boss, Frank Waturi (Dan Hedaya). Joyless, listless, and chronically sick, Banks regularly visits doctors who can find nothing wrong with him. Finally, Dr. Ellison (Robert Stack) diagnoses an incurable disease called a "brain cloud" which has no symptoms, but will kill Joe within five or six months. Ellison says that Joe's ailments were psychosomatic, caused by his horrific experiences in his previous job as a firefighter. Ellison advises him, "You have some life left...live it well." Joe tells his boss off, quits his job, and asks former coworker DeDe (Meg Ryan) out on a date, but when he tells her that he is dying, she becomes very upset and leaves.
In Edinburgh, Scotland, in 1880, Professor Sir Oliver Lindenbrook (James Mason), a geologist at the University of Edinburgh, is given a piece of volcanic rock by his admiring student, Alec McEwan (Pat Boone). Deciding that the rock is unusually heavy, Lindenbrook, mostly thanks to the carelessness of his lab assistant, Mr. Paisley (Ben Wright), discovers a plumb bob inside bearing a cryptic inscription. Lindenbrook and Alec discover that it was left by a scientist named Arne Saknussemm, who had, almost 300 years earlier, found a passage to the center of the Earth. After translating the message, Lindenbrook immediately sets off with Alec to follow in the Icelandic pioneer's footsteps.
On the fictional Pacific island of Talua in French Polynesia, some 500 miles from Tahiti, Father Doonan (Spencer Tracy), has been relieved of his duties by Father Perreau (Kerwin Mathews). Father Doonan has fallen out of favor with the island's residents because he stumbled on the island's carefully hidden secret: Hansen's Disease (leprosy) among the children of the islands. He built a hospital for the children by the island's volcano.
Shelby Gilmore (William Holden), who owns a newly constructed hotel on a remote Pacific island, wants desperately to marry his secretary, Kay Kirby (Jacqueline Bisset) and proposes to her under the impression that she'll become his seventh wife. Kay is in love with Hank Anderson (Paul Newman), an oil rigger whose scientists are warning him that a nearby active volcano is about to erupt.
Andre Laurence (Jourdan) takes a trip to a Polynesian island with his college roommate Tenga (Chandler). He assumes the native life and marries his friend's sister, Kalua. An eruption of a volcano and the Kahuna, the island's shaman, decides that the volcano can be appeased with the sacrifice of Kalua.
In the time of Jesus Christ, blacksmith Marcus (Preston Foster) is content with his life, beautiful wife Julia (Gloria Shea) and six-month-old son. However, when Julia and their child are run down by a chariot in the streets of Pompeii, Marcus spends the little money he has to pay for a doctor and medicine. Needing more, in desperation, he becomes a gladiator. He wins his fight, but in vain; his wife and child die.
As a yacht sails into an island chain in the South Pacific, a large number of natives in pontoon boats sail out to greet them. The natives dive for the trinkets the yacht's crew throws them. A shark arrives, scaring most of the natives away. In an attempt to catch a shark by throwing it bait that has been tied to a harpoon-sized hook, Johnny Baker (Joel McCrea) accidentally steps into a loop that tightens around his ankle. The shark takes the bait, and the rope grows tighter, causing the rope to yank the young man overboard. Luana (Dolores del Río), the daughter of the chief, saves his life by leaping into the water and cutting the rope.