Transform Plate Boundaries are locations where two plates slide
past one another. The fracture zone that forms a transform plate boundary
is known as a transform fault. Most transform faults are found in the
ocean basin and connect offsets in the mid-ocean ridges. A smaller number
connect mid-ocean ridges and subduction zones.
Transform faults can be distinguished from the typical strike-slip
faults because the sense of movement is in the opposite
direction (see illustration above). A strike-slip fault
is a simple offset, however, a transform fault is formed
between two different plates, each moving away from the
spreading center of a divergent plate boundary. When you
look at the transform fault diagram above, imagine the double
line as a divergent plate boundary and visualize which way
the diverging plates would be moving.
A smaller number of transform faults cut continental lithosphere.
The most famous example of this is the San Andreas Fault
Zone of western North America. The San Andreas connects
a divergent boundary in the Gulf of California with the
Cascadia subduction zone. Another example of a transform
boundary on land is the Alpine Fault of New Zealand. Both
the San Andreas Fault and the Alpine Fault are shown on
our Interactive Plate
Transform faults are locations of recurring earthquake activity and faulting.
The earthquakes are usually shallow because they occur within and between
plates that are not involved in subduction. Volcanic activity is normally
not present because the typical magma sources of an upwelling convection
current or a melting subducting plate are not present.