A slip-strike fault may have been the beginning of the rifting, but without the rifting, the Baja would have just slid north, like the land west of the San Andreas.
Perhaps you should have taken a Historical Geology class.
How Did the Gulf of California Form So Quickly Seafloor Spreading Ocean Rifting How Oceans Form Baja California Formation
Finally, strike-slip faulting (as happens perhaps most famously along the San Andreas Fault) is common in the region and likely to have played a major role in rupturing the Gulf of California.
"Strike-slip faults by nature are steep" — commonly near-vertical — "so they have a tendency to cut efficiently through the crust and into the mantle," which focuses the breaking along very narrow zones, Umhoefer explained.
Altogether, his study concluded, these assets combined to rift and rupture the Gulf of California at a rapid pace.
Rifting worldwide
Globally, these factors also account for stark differences between rifts at active continental margins and those in the middle of a continent, Umhoefer said.
Areas that are tectonically active before
rifting begins — which usually lie at continental margins — rupture rapidly and form smaller seas, such as the Gulf of California, because they rift off small pieces of continent. Rifts that begin in the middle of a continent slowly rupture and form larger basins, as in the case of the formation of the Atlantic Ocean, because they tend to break off large chunks of continental crust.
"How do continents that have active tectonics, like western North America, respond to rifting versus a place that's been relatively quiet? That's a question the research community is trying to answer," Umhoefer said.
