Chapter Ten Terrigenous Sediments

Abstract

Publisher Summary This chapter focuses on terrigenous sediments and describes the physical and chemical weathering of the earth's surface and the removal and transport of terrigenous elements. Physical weathering breaks the surface of the parent rock into small fragments with no changes in chemical composition, and is caused by several processes. Physical weathering processes are especially efficient in regions of extreme climatic conditions, such as arid to semi-arid tropical deserts, and cold high-latitude and mountain areas. Chemical weathering is an alteration of the uppermost parent rock by chemical reactions. The minerals react with rainwater, which has a pH of about 5.7 and pO 2 and pCO 2 in equilibrium with those of the atmosphere. The reaction of rainwater with surface minerals beings gradual, chemical weathering progresses through time as more soluble elements are removed. A driving force of continental weathering, rainwater is also a major agent of erosion and evacuation of terrigenous particles to the ocean. The efficiency of rainwater as an agent of erosion is directly related to the intensity of the precipitation and the velocity of raindrops, which increases with the diameter of the drops and the velocity of the wind.