Cliffs are formed as erosion landforms by the processes of weathering and erosion. These volcanic areas are characterised by basalt bedrock and dark soils derived from its weathering. Cliffs are usually formed by rock that is resistant to weathering and erosion. Joints have a profound control on weathering and erosion of bedrock. Most obvious perhaps are the water driven processes of weathering and erosion. Zeolites transform to other minerals under weathering, hydrothermal alteration or metamorphic conditions. The Qattara Depression was created by the interplay of salt weathering and wind erosion. The rock consists of phyllites and schists, and is highly susceptible to weathering and erosion. Climate directly affects the rate of weathering and leaching. These processes include partial melting, crystallization, fractionation, metamorphism, weathering, and diagenesis. Erosion also takes place in connection with weathering and cavitation. Vermiculite forms by the weathering or hydrothermal alteration of biotite or phlogopite. New soils increase in depth by a combination of weathering, and further deposition. Carbonation is therefore a large feature of glacial weathering. Lichens on rocks are thought to increase chemical weathering rates.