Introduction

The process of weathering alters rocks at or near the surface of the Earth, transforming hard rocks into soft material that can be removed easily (Fig. 5.1). Rocks, which are formed at various depths inside the Earth’s crust under conditions of high pressure and temperature, undergo a series of physical and chemical changes when they are exposed to the atmosphere at or near the surface of the Earth where much lower temperate and pressure prevail. The term ‘weathering’ encompasses the full range of such changes. A formal definition can be constructed as