ABSTRACT
The chapter firstly deals with tectonic processes. The Earth’s crust is formed of moving plates at the edges of which earthquakes and volcanic activity are common. In the centre of oceans new crust is formed; at the edge of oceans the crust sinks back into the mantle. As continents collide, mountains form. The chapter then focuses on weathering and erosion processes. Weathering by physical and chemical processes wears down rock, with climate and rock type being important controls of weathering process rates. Erosion transports weathered material by water, wind and by mass movements. Soils slowly accumulate, being products of weathering and biological inputs, and are made up of minerals from weathered rock, organic matter, water and air. Soil formation is affected by climate, the parent material, topography and organisms. The texture, structure and chemistry of a soil are crucial in determining its water and nutrient exchange capacity and hence its ability to support plant growth. However, human action can cause rapid and widespread degradation of soils. Therefore, careful soil management is required to ensure sustainable food supplies, good water quality and reduced loss of soil carbon to the atmosphere.
