Transform fault

Article By:

Lonsdale, Peter Scripps Institution of Oceanography, La Jolla, California.

Last reviewed:December 2019

DOI:https://doi.org/10.1036/1097-8542.704900

One of the three fundamental types of boundaries between the mobile lithospheric plates that cover the surface of the Earth. Whereas spreading centers mark sites where crust is created between diverging plates and subduction zones are where crust is destroyed between convergent plates, transform faults separate plates that are sliding past each other with neither creation nor destruction of crust. The primary tectonic feature of all transform faults is a strike-slip fault zone, a generally vertical fracture parallel to the relative motion between the two plates that it separates. Strike-slip fault zones are described as right-lateral if the far side is moving right relative to the near side (for example, the Queen Charlotte zone; Fig. 1), left-lateral if it is moving to the left (for example, the North Caribbean zone; Fig. 1). Not all such fault zones are plate-bounding transform faults. Small-scale strike-slip faulting is a common secondary feature of many subduction zones, especially where plate convergence is oblique and of some spreading centers, especially those with propagating rifts; it also occurs locally deep in plate interiors. The distinguishing characteristic of a transform fault is that both ends extend to a junction with another type of plate boundary. At these junctions the divergent or convergent motion along the other boundaries is transformed into purely lateral slip. See also: Earth crust; Plate tectonics; Subduction zones

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