SOIL SURVEY

-173-Cryoturbation (Congeliturbation) - Ground surface modified by processes of fros taction .Drainage, soil - See soil drainage classes .Drift, glacial - See glacial drift .Drumlin - An elongated or oval hill of glacial drift, commonly till, deposited byglacier ice with its long axis parallel to the direction of ice movement .Edaphic - (i) of or pertaining to the soil . (ii) resulting from, or influenced by ,factors inherent in the soil or other substrate rather than by climatic factors .Eluvial horizon - A soil horizon that has been formed by the process of eluviation .In Yoho these horizons are generally light colored and found directly underthe forest litter .Eluviation - The transportation of soil material in suspension or in solution withi nthe soil by the downward or lateral movement of water .Erosion - The wearing away of the land surface by running water, wind, ice o rother geological agents including such processes as gravitational creep . I tincludes both normal and accelerated soil erosion . The latter is brought aboutby changes in the natural cover or ground conditions and includes those due t ohuman activity (see Agric . Can . 1976) .Esker - A winding ridge of irregularly stratified sand, gravel and cobbles depositedunder the ice by a rapidly flowing glacial stream .Evapotranspiration - The loss of water from a given area during a specific time b yevaporation from a soil surface and by transpiration from plants . Potentialevapotranspiration is the maximum transpiration that can occur in a give nweather situation with a low-growing crop that is not short of water and doesnot completely shade the ground .Exchange capacity - The total ionic charge of the adsorption complex that is activein the adsorption of ions - see cation exchange capacity .Fan - A fan-shaped form that can be likened to the segment of a cone, and possessin ga perceptible gradient from apex to the toe . Fans commonly occur where ther eis a notable decrease in gradient .Fibric layer - A layer of organic soil material containing large amounts of weakl ydecomposed fibre whose botanical origin is readily identifiable .