Rg. Gordon, THE PLATE TECTONIC APPROXIMATION - PLATE NONRIGIDITY, DIFFUSE PLATE BOUNDARIES, AND GLOBAL PLATE RECONSTRUCTIONS, Annual review of earth and planetary sciences, 26, 1998, pp. 615-642
The central assumption of plate tectonics, that plate interiors are ri
gid, remains a useful but uncertain approximation. Strain rates of sta
ble plate interiors are bounded between 10(-12)-10(-11) year(-1) and s
imilar to 4 x 10(-10) year(-1). The narrowness of all plate boundaries
, the other main assumption of plate tectonics as originally conceived
, is contradicted by many observations, both in the continents and in
the oceans. Some diffuse plate boundaries in both continents and ocean
s exceed dimensions of 1000 km on a side. Diffuse plate boundaries cov
er similar to 15% of Earth's surface. The maximum speed of relative pl
ate motion across any one diffuse plate boundary ranges from similar t
o 2 to similar to 15 mm/year, which is faster than some upper bounds o
n intraplate motion across stable plate interiors (less than or equal
to 2 mm year(-1)). Strain rates in diffuse plate boundaries can be as
high as similar to 10(-8) year(-1), similar to 25 times higher than th
e upper bound on strain rates of stable plate interiors, but similar t
o 600 times lower than the lowest strain rates across typical narrow p
late boundaries. The poles of rotation of the plates flanking a diffus
e oceanic plate boundary tend to be located in the diffuse boundary, w
hich is a consequence of the strong coupling across the boundary.