Weathering- the physical and chemical breakdown of rocks. Involving an interaction between the 4 spheres of the earth. Weathering involves specific processes acting on rock materials at or near the surface of the earth. Mechanical weathering (1) rocks break into pieces (2) changing size and shape (3) but not their composition. Frost action -the freezing and thawing causes alternate expansion and contraction of rocks eventually breaking them apart. ~ removal of important chemical compounds from the rock. ~ high in iron, prone to oxidizing (rusting) ~ oxides are very common in sedimentary rocks. First to crystallize are least stable to weathering. ~ hotter and wetter climates have faster chemical weathering. ~ regolith encompasses all unconsolidated material at the surface, fertile or not. ~involves chemical, physical, biological processes to breakdown rocks. ~ climate, topography, source material composition, and time are factors. Soil losses in u. s. amount to billions of tons per year about 0. 04 cm per year.