Chemical Weathering - the transformation of rocks and minerals exposed to water and air into new chemical products. Role of Oxygen - rusting of an iron nail exposed to dampness and air is a simple example of chemical weathering. If water is present iron oxide combines with water to form limonite. Role of Acid - Natural acids disrupts the atomic structure of many minerals. The source of natural acid for rock weathering is dissolved carbon dioxide in water.
Acid causes feldspars to alter to clay.
Solution weathering - some minerals such as calcite will dissolve in water. Soil - the layer of weathered, unconsolidated material on top of bed rock. Soil Horizons -layers of soil are distinguishable by characteristic physical or chemical properties. A horizon - the zone of leaching characterized by the downward movement of water. B horizon - the zone of accumulation of material leached downward from the A horizon.