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Soils have a natural characteristic called the cation exchange capacity (CEC) that allows them to hold (and exchange) cations (e.g., Ca+2 or Na+). These cations are held tight enough on the CEC that ...

Perspective -- Geologic time : The quaternary period ; Archeology ; Estimating geologic time ; Early estimates of geologic time -- Weathering and erosion : Structure of the rocks ; Structure in ...