The Gulf of California is a classic place to study the early stages of the opening of an ocean basin. This animation depicts the evolution of the spreading ridge that marks the boundary between the Pacific and North American Tectonic Plates. The spreading ridge and transform faults are defined, then we go back 20 million years, borrowing an animation from Tanya Atwater (emvc.geol.ucsb.edu) to see changes in the Baja peninsula and the breakup of the continental shelf. The on-land part of this submarine spreading ridge extends into Baja California, Mexico and the Imperial Valley of California where it is transitioning from ridge-transform boundary to the continental boundary.
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In a strike-slip fault, the movement of blocks along a fault is horizontal. The fault motion of a strike-slip fault is caused by shearing forces. Other names: transcurrent fault, lateral fault, tear fault or wrench fault. Examples: San Andreas Fault, California; Anatolian Fault, Turkey.
New oceanic crust is created at this boundary when basalt magma, formed in the mantle, rises into fractures in the crust and solidifies. Spreading ridges are high elevation because the young oceanic plate at the ridge crest is hot and less dense than the older, colder and more dense plate on the flanks of the ridge.
A transform fault is a type of strike-slip fault wherein the relative horizontal slip is accommodating the movement between two ocean ridges or other tectonic boundaries. They are connected on both ends to other faults.