Why is part of California separating from the rest of North America?

Answer 1

California is not separating from North America so much as rubbing up against it. The state of California straddles two tectonic plates: the North American Plate and the Pacific Plate. The place where these two plates come into contact, the San Andreas Fault, is called a transform fault: the North American Plate and the Pacific plate grind back and forth against each other, sometimes creating earthquakes. Since part of California, including San Francisco and Los Angeles, are actually located on the Pacific Plate side, this part of the state is technically separate from the rest of North America already. It doesn't appear that way, since the two plates are pressed against each other, but the North American Plate and the Pacific Plate do move independently of each other, so that section of California is slowly changing its alignment relative to the rest of North America.