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CORE DEFINITIONS LOOP Weathering = breakdown of rock at or near Earth’s surface Erosion = removal of rock by water, wind, glaciers, gravity Mechanical weathering = physical breakdown of rock Chemical weathering = decomposition by chemical change Frost action = water expands 9 percent when frozen Soil = mix of sand, clay, humus from weathered rock A horizon = leaching, darkest, most humus B horizon = accumulation C horizon = broken bedrock Farther from shore = finer sediment