ATTERNS AND PROCESSES IN THE PHYSICAL ENVIRONMENT 6.1 Weathering and erosion
Weathering is a process that breaks down rocks into smaller pieces.
Weathering and erosion are both exogenic (external) forces responsible for shaping and reshaping the landscape already made by endogenic (internal) forces. This means that weathering and erosion operate on the surface of the earth as opposed to inside it.
Both erosion and weathering are called agents of denudation as they wear away
the rocks of the landscape and gradually change its surface. Weathering is the process that breaks down rocks into smaller pieces. The broken
rocks are then deposited where they fall. Weathering does not transport material; instead it is transported by the agents of erosion or by the action of gravity (mass movement). Weathering agents include frost, extreme changes of temperature and chemical
reactions with oxygen, carbon dioxide and water. Erosion is the process by which the earth’s rocks are broken down, transported and deposited elsewhere. Erosion agents are rivers, ice, sea and wind.
6.2 Weathering Types of weathering
Mechanical weathering: This breaks down rocks into smaller pieces. No new substances are formed. It is a physical disintegration (falling apart) of rock.
Chemical weathering: A chemical reaction occurs in the rock causing it to decompose. New substances are formed.
Biological weathering is the disintegration of rocks due to the physical and/or chemical actions of living things. The types of living things that can cause weathering range from bacteria to plants and animals.
Mechanical (rocks disintegrate)
Freeze-thaw Onion weathering Crystallisation of salts
Chemical (rocks dissolve or rot)
Carbonation Hydration Oxidation Hydrolysis
1. Mechanical weathering There are three processes of mechanical weathering.
Fig. 1 This sandstone rock has been weathered into an unusual shape at the Garden of the Gods, Colorado Springs, USA.