Up until this point, you have been studying how forces from within the Earth (endogenic forces) have altered the Earth’s surface through creating tectonic landscapes. In this chapter, you will begin studying how forces on the surface – namely weathering and erosion – gradually break down these landscapes. These are known as exogenetic forces. Although we think of rocks as permanent features, they are gradually changed and destroyed by the Earth’s environment over a long time. This wearing down of rocks by the Earth’s environment is called weathering.
KEY WORDS
l Weathering l Erosion l Physical l Chemical l Disintegration l Decomposition l Freeze-thaw action
l Exfoliation l Carbonation l Hydrolysis l Hydration l Oxidation l Expansion l Contraction
LEARNING OUTCOMES
What you MUST know l The difference between weathering and erosion
l Two processes of physical weathering l Two processes of chemical weathering
What you SHOULD know l Examples of where each process occurs l The difference between disintegration and decomposition
What is USEFUL to know l How to identify the type of weathering from a photograph
Introduction
In this chapter, we will look at the various processes that weather rock. The processes are slow. Rocks are gradually broken down by the Earth’s environment through the processes of weathering and erosion.
Weathering is the breaking up and decay of rocks on the Earth’s surface through natural mechanical and chemical processes.
PATTERNS AND PROCESSES IN THE PHYSICAL ENVIRONMENT 129 GEO DICTIONARY
Erosion: the breaking down and transportation of rock by water, wind and ice
l Diurnal range l Carbonic acid l Calcium carbonate l Calcium bicarbonate l Karst l Kaolin l Feldspar
