The novel incorporates an extensive essay on the history and culture of California from the vantage point of a future date when the state has disappeared.
The novel describes, in retrospect, the history and culture of California from its earliest days, and its influence on the rest of the United States and the world when - after an unspecified date in 1969 - the state suffers a Richter magnitude 9 earthquake and the populous coastal regions west of the San Andreas Fault sink into the Pacific Ocean.
After the event, the narrative switches to "present tense" news radio and television coverage of the event using a literary convention of "changing the dial / channel" from one news report to another, to cover the disaster: The Central Valley is inundated by the sea; the Embarcadero Freeway and Coit Tower have collapsed, along with the Oakland Bay Bridge.
As this narrative closes, two more disasters occur nearly simultaneously: The Oroville Dam bursts, and in the twilight of the day, a passenger jet over San Bernardino is pulled out of the sky by turbulence, as the pilot tries to describe the sight of the San Andreas Fault splitting open in the dusk (and, as is made clear in the final chapter, the pilot was witnessing Southern California slide into the sea).
As a result of its publication, some religious believers in the Los Angeles region decided to move away, in fear of its fictional events actually occurring.