Answer to Question 1
Geologists commonly define soil as a layered mixture of loose mineral and organic constituents that have different physical and/or compositional properties than the original non-weathered material.
Engineers define soil as any surface material that is not solid rock and would include all of the geological soil plus any unconsolidated sediment. Soil scientists define soil as a medium for plant growth and would include all of the geological soil plus synthetic plant growth mediums.
Answer to Question 2
AOEBC are the principle horizons. A (accumulation of leaf matter) is the layer that includes organic matter derived from accumulating leaves and branches. The O (organic) layer is organic material only, and can overlie the A layer where plant growth is dense. The E (eluviation, or washing out) horizon is pale in color, reflecting the absence of organic matter, easily weathered minerals, and clay minerals. It may or may not be present, below the A horizons. The B horizon is recognized by its usual red color, and the accumulation of minerals that are not present in the parent material such as calcite and clay minerals. The C horizon is the lowermost layer, least weathered, and provides parent material for soil formation.
The Geologic Time Scale
Soil Cleans Water
Soil Texture Diagram
Soil pH
The Geologic Repository at Yucca Mountain, Nevada
The Geologic Time Scale