Clay between silts and clays based on the plasticity properties of the soil, as measured by the soils' Atterberg limits. ISO 14688 grades clay particles as being smaller than 2 μm and silt particles as being larger. Mixtures of sand, silt and less than 40% clay are called loam. Loam makes good soil and is used as a building material. Clay minerals typically form over long periods of time as a result of the gradual chemical weathering of rocks, usually silicate-bearing, by low concentrations of carbonic acid and other diluted solvents. These solvents, usually acidic, migrate through the weathering rock after
Godalming of the town centre steep hills reach 95 m (311.67 ft) AOD from 40-45m (131.23-147.63 ft) AOD in the town centre itself. In terms of rock and mineral structure, the soil is Gault Clay superimposed by Upper Greensand, Claygate Beds and Bagshot Sands; throughout the narrow east-west middle valley of Godalming and its wide northeast suburbs (Farncombe and Catteshall) the rocky head geological deposit is also found; angular pieces of rock and soil derived locally from the extensive frost-shattering of rocks and the subsequent movement of this material down valley slopes. Soil is mostly, i.e. on the upper slopes of