Folding with thermal-mechanical feedback: A reply

A unified theory of deformation at all scales is outlined. Processes operating during deformation and metamorphism can be coupled in the form of reaction-diffusion equations. Solutions to these equations depend on the specific processes that dominate the dissipation of energy. Hobbs et al. (2008) is concerned with a scale where deformation and conduction of heat dominate and this corresponds to the regional scale. Other papers present results for other length and time scales. Boudinage develops through these processes in materials where the strict Biot theory predicts no boudinage. The strict Biot theory is applicable only at the instant of instability and provides no information on the subsequent growth of the folds. Analytical results for growth to large amplitudes show that only one wavelength develops and not a spectrum of wavelengths as proposed by Treagus and Hudleston (in press) and others. The wavelength to thickness ratio that finally develops is strongly dependent on boundary conditions and so such ratios tell us nothing about the conditions of folding unless these boundary conditions are known. The processes involved in folding with thermal-mechanical feedback are identical for single- and multi-layer systems so that it requires little space to expand the discussion to multi-layers.