Plot
In downtown Los Angeles, an earthquake strikes. Michael "Mike" Roark, the new director of the city's Office of Emergency Management, insists on coming to work to help with the crisis even though he has been on vacation with his daughter, Kelly. His associate, Emmit Reese, notes that the quake caused no major damage, but 7 utility workers are later burned to death in a storm drain at MacArthur Park. As a precaution, Roark tries to halt the subway lines near the location of the earthquake, though MTA Chairman Stan Olber believes that there is no threat to the trains. Roark then takes it upon himself to investigate the storm drain, accompanied by his co-worker Gator Harris. As they explore, the storm drain begins to shake violently and hot gases begin to fill the tunnel. Roark and Harris barely escape and order a complete evacuation from the park. Roark then calls in Seismologist Amy Barnes, who believes that a volcano may be forming beneath the city as the earthquake opens a fissure in the fault line, to which magma can potentially rise through it, but she has insufficient evidence to make Roark take action.
The next day at 5:14am, Amy and her assistant Rachel venture into the storm drain to investigate. As they collect samples, the San Andreas Fault unleashes a strong earthquake that strikes the city. A power outage occurs across the entire city, and a subway train derails from falling debris. Rachel falls into a crack caused by the quake and is killed by a rush of hot gases. Later, as Roark and Kelly drive down Wilshire Boulevard, hot steam bursts from the manholes and ash starts falling from the sky as the La Brea Tar Pits boils with massive smoke and meteors launch into the city, setting buildings on fire and destroying a fire truck, overturning it with a firefighter trapped inside. Roark helps the injured civilians and after another strong earthquake, a small cinder cone volcano is formed and erupts from the Tar Pits. Lava then begins to flow freely down Wilshire, incinerating everything in its path and killing two firefighters in the overturned fire truck. Roark and Kelly become separated, as she is injured when a lava bomb burns her leg and is taken to Cedars-Sinai Medical Center along with other patients, while Roark stays behind to help the people evacuate Wilshire.
Meanwhile, Stan leads his team through the Red Line subway tunnel to the derailed train to search for survivors. As they help the unconscious passengers onboard, they discover that lava is flowing through the tunnel and evacuate the passengers off the train. Stan realizes the driver is still on the train and goes back in to save him just as the lava reaches the train and begins melting it. Stan carries the unconscious driver through the train back to his team, but realizes the lava has flowed too far for him to jump to safety. With no other option, Stan sacrifices his life by jumping into the lava flow before he tosses the driver to safety.
Roark, Amy and LAPD lieutenant Ed Fox devise a plan to use concrete barriers to create a blockade at the end of Wilshire, which obstructs the lava, preventing it from flowing down Fairfax Avenue and doing further damage to the city. A team of firefighters use all the water from their hoses and a fleet of helicopters dump gallons of water collected from the Pacific Ocean to subdue the lava and volcano, forming a crust and making the plan a success. However, Amy thinks that magma is still flowing underneath the city because ash is still falling. When Roark helps Amy confirm her suspicions, they discover that lava is flowing fast through the Red Line subway system. Amy then predicts that another eruption will occur at the end of the tunnel at Cedars-Sinai and, after calculating the speed of the flowing lava, determines that it will reach the end of the tunnel in 30 minutes.
Roark devises another plan to demolish a 22-story condominium building using explosive charges to create a "dam" in order to block the lava from flowing toward the hospital and the rest of the West Side, thus diverting it into the Ballona Creek storm drain which leads directly into the Pacific Ocean. As a demolitions team plant the charges, the lava reaches the end of the tunnel and a massive eruption occurs, endangering the patients on the street. With only seconds left, they detonate the charges in the ground to create a trench for the lava flow, while Gator Harris and an LAPD Bomb Squad officer (trapped under debris) sacrifice their lives to detonate the final charges in the building. Roark then spots Kelly nearby, trying to retrieve a little boy she was watching who wandered off. The two are directly in the collapsing building's path. Roark barely manages to save them from being crushed. The plan succeeds, and the lava flows down Ballona Creek directly into the ocean, shutting down the volcano and ending the eruption. After the dust settles, the sky opens up and starts raining. Roark, Kelly, and the boy emerge from the rubble unscathed and reunite with Amy before heading home, while Emmit and his associates stay to help the survivors.
Meanwhile, at the Tar Pits, the volcano (now being named "Mount Wilshire") has taken shape above ground and remains active.
