Physical and Chemical Weathering

Abstract

As one geologist exclaimed: “Savor the irony should the metamorphic muscles that push mountains to the sky be driven by the pitter patter of tiny raindrops.” In the following chapters we look at this pitter patter, a synonym for exogenic processes that shape our landforms, starting with the most important process: weathering. Weathering takes place through a combination of both mechanical and chemical means. We have all experienced the results of weathering in day-to-day life whether you stumble over a tree root that broke the asphalt on your morning run or you hear the sharp sound of a rock splitting apart in the silence of a freezing mountain night. But the fate of Cleopatra’s needle, a collective, popular name of three New Kingdom Egyptian obelisks that were transferred from Egypt to the damp cities of New York, London and Paris during the colonial era of the nineteenth century illustrate that weathering is obviously a strong function of climate, the properties of the parent rock, the presence or absence of soil, and time. This chapter is mostly illustrated with photography because the small-scale details of the weathering process are difficult to capture with images from space. Nevertheless, some large-scale weathering forms may well be detected from space as pictures of exfoliation patterns or corestone weathering show.