Subglacial till: A physical framework for its properties and processes

The continuum theory of mixtures provides a framework around which present knowledge of subglacial till can be organized. The proposed framework is provisional in two senses: the constitutive description of till will require improvement, and not all potentially significant processes have been included. Till is treated as a three‐component mixture of water, clasts (coarse‐grained solids), and fine‐grained matrix solids. These components obey mass balance equations, and their behavior is subject to constitutive relations that describe such processes as Darcian water transport, fine‐grained sediment transport, consolidation, shear deformation, dilatancy, and comminution. Five state variables uniquely determine the compressibility, permeability, shear strength, and other physical properties. Numerical solutions of the state evolutions equations illustrate that the properties of till are highly responsive to changes in the subglacial environment.