ABSTRACT
The full impact of global warming depends on the uncertain reaction of Earth's cryosphere. Cryoturbation refers to soil mixing whereby soil surfaces become unstable, soil materials are mixed internally, and soil horizons are disrupted and displaced. The combination of summer drying and winter cryogenic activities gives the granular structure at the surface. In the autumn subsoils lose water to a freezing front at the surface and a freezing front at the permafrost below; they are under considerable cryostatic pressure between the two freezing fronts. Earth hummocks are formed when cryogenic processes are only periodically active. Glaciation and global icehouse conditions are a recurring Earth surface state and not a climatic abnormality or ‘accident’. The modern glacial revolution recognizes worldwide glaciation not only as an important, if intermittent, feature of Earth's physical environment but as providing an icehouse counterpart to long periods of greenhouse Earth.
