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A region of lithosphere approximated as rigid on the spatial and temporal scale of a plate-kinematic model. Its instantaneous motion on a sphere is a rotation; deformation within boundary zones limits the rigid-plate approximation.

Increase in crust or lithosphere thickness through tectonic deformation, including crustal shortening and stacking by thrust faults.

Suppose a compensated vertical column contains thickness $L$ of material warmed by $\Delta T$. For a small anomaly, the volumetric thermal expansion coefficient gives $\delta \rho \simeq -{\rho }_s\alpha \Delta T$. Its column mass change is $\delta M\simeq -{\rho }_s\alpha \Delta TL$. Define ${\rho }_{\mathrm{ref}}\Delta H$ to be the additional column mass associated with the permitted uplift and interface motion in the chosen isostasy model. The mass balance ${\rho }_{\mathrm{ref}}\Delta H+\delta M=0$ proves the displayed scaling.

The model must specify ${\rho }_{\mathrm{ref}}$: translating an upper column of fixed internal thickness above mantle compensation gives a mantle-density scale, while fixing an internal interface and changing only surface-layer thickness gives that surface layer's density scale. If their ratio is near one, $L=7$ km, $\Delta T=350$ K and $\alpha =10^{-5}{\mathrm{K}}^{-1}$ imply only about 25 m of relief. Extending this to a whole lithosphere requires its depth-dependent temperature anomaly, not only the mean temperature anomaly of the crust. Dynamic topography and flexural stresses lie outside a simple local-column calculation.

A plate boundary at which relative motion is tangential to the boundary. It neither creates nor consumes lithosphere in the ideal kinematic model. The admissible junction velocities form a line parallel to the fault through either adjacent plate velocity in velocity space.