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Describe the characteristics of chalk and the land forms typical of chalk areas

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Introduction

Describe the characteristics of chalk and the landforms typical of chalk areas Chalk is a soft white or whitish form of limestone, composed of the remains of small marine organisms. It formed after the shells and skeletons of these organisms were deposited in a thick layer on the sea bottom. Chemically, chalk is almost pure calcium carbonate with traces of other minerals. It ranges in hardness and texture from very soft porous varieties to harder close-grained types. ...read more.

Middle

This is the reason why distinctive rolling hills and vales are common in chalk scenery areas. Chalk scenery is also closely associated with the development of escarpments or cuestas which have steep scarp slopes and gentle dip slopes. However these features are more a product of erosion than of weathering. As with all limestone scenery, there is little surface drainage on chalk. Dry valleys are common features, and the size of these suggests different climatic conditions in earlier times. ...read more.

Conclusion

* The freezing of water in rock pores during glacial periods caused the chalk to become impermeable and allowed surface drainage to develop. Later, as temperatures rose and ice melted, the chalk once again became permeable causing the surface streams to disappear, leaving dry valleys behind. * The streams and their valleys developed on an overlying layer of impermeable rock. This layer was removed by a combination of weathering and erosion, resulting in the valleys being gradually superimposed on the underlying permeable chalk. * Surface drainage developed during periods of significantly higher rainfall than at present. When the rainfall decreased the water-table dropped, leaving behind dry valleys. ...read more.

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