Those of us who live in the Los Angeles region
know that this is an area of active tectonics. We
have earthquakes; we have many large mountains
nearby that are testimony to the great power of
the forces that are moving and deforming the
surface of the earth here; and we have the San
Andreas fault as our local tourist attraction. But
this great fault is not just local. Besides extending
northward it also continues south toward the
Gulf of California, where a series of structures
represents its continuation under water. All of
these structures are part of the major boundary
between the Pacific plate and the North America
plate. So even though we don't think of Los
Angeles and the Gulf of California as being similar
in many ways, they're tectonically connected
because they sit on the same plate boundary and
suffer many of the same kinds of deformation due
to motions between these two plates
