  We develop a sine-Gordon model of layered systems of two-dimensional
modulated surfaces and one dimensional stripes, and demonstrate that these
systems can undergo a Kosterlitz-Thouless transition in which the modulations
unlock as a result of thermal or quantum fluctuations, respectively. The
unlocked phase is interpreted as an anisotropic crystal in which
soliton-antisoliton pairs proliferate. The properties of such a state for
modulated stripes in quantum Hall systems and its possible relevance to recent
anomalies in transport data are discussed.
