Can California Become an Island? No.

Geologic Reality Check

California is firmly attached to the North American Plate. The San Andreas Fault is a transform boundary where the Pacific Plate slides northwest past the North American Plate—not a rift that could open an ocean. Even over millions of years, the most that happens is Los Angeles sliding past San Francisco; the crust does not split to create a new seaway. So, California will remain continental forever.