This textbook describes the physics of the plastic deformation of solids at high temperatures. It is directed at geologists or geophysicists interested in the high-temperature behaviour of crystals who wish to become acquainted with the methods of materials science in so far as they are useful to earth scientists. It explains the most important models and recent experimental results without losing the reader in the primary literature of materials science. In turn the book deals with the essential solid-state physics; thermodynamics and hydrostatics of creep; creep models and their applications in the geological sciences; diffusion creep; superplastic deformation and deformation enhanced by phase transformations. Five concluding chapters give experimental results for metals, ceramics and minerals. There are extensive bibliographies to aid further study.