Geology Reference
In-Depth Information
Slip-sliding along: Transform plate boundaries
Sometimes, where the edges of two plates meet, they are neither moving toward one an-
other nor away from one another. Instead, they are just sliding in opposite directions.
This type of plate boundary is called a
transform boundary
and is illustrated in Figure
9-7.
Figure 9-7:
Features of a
transform bound-
ary.
At transform boundaries, the interaction between the two plates is much more subtle;
there is no direct pushing, no subduction, no stretching of the plates, and no production
of new rocks from magma.
Earthquakes are common at transform boundaries as the plates grind, slip,
and slide past one another. The earthquakes occur very close to the surface (be-
cause there is no subduction) and can be very powerful.
An example of a transform boundary is the San Andreas Fault in California, pictured in
this topic's color photo section. Along this fault, shallow earthquakes are common as
the North American Plate slides past the Pacific Plate.
Transform boundaries, or
transform faults,
also occur along mid-ocean ridge divergent
boundaries. These transform boundaries associated with mid-ocean ridges are called
fracture zones.
As the two oceanic plates move apart, stretching the newly created
