2.1 - Processes of Weathering - Introduction
Have you ever considered how rock becomes soil? What would happen to human civilization, food and fiber production if the processes we call weathering ceased to occur? The processes of weathering are critical to soil formation.
- Describe how climatic factors influence the weathering of rocks and minerals.
- Define and distinguish physical, chemical, and biological weathering processes.
How do rocks become soil? How does the climate in places such as Peru, Alaska, and Algeria influence the weathering of rock? These questions are critical in understanding the roles weathering processes and climate play in the disintegration of rocks and minerals to begin the process of soil formation.
Weathering is the process of disintegration of rock from physical, chemical, and biological stresses. Weathering is influenced by temperature and moisture (climate). As rock disintegrates, it becomes more susceptible to further physical, chemical, and biological weathering due to the increase in exposed surface area. During weathering, minerals that were once bound in the rock structure are released.
The degree of weathering that occurs depends upon the resistance to weathering of the minerals in the rock, as well as the degree of the physical, chemical, and biological stresses. A rule of thumb is that minerals in rocks that are formed under high temperature and pressure tend to be less resistant to weathering, while minerals formed at low temperature and pressure are more resistant to weathering. Weathering is usually confined to the top few meters of geologic material, because physical, chemical, and biological stresses generally decrease with depth. Weathering of rocks occurs in place, but the disintegrated weathering products can be carried by water, wind, or gravity to another location (i.e., erosion or mass wasting).
This lesson was developed by Martha Mamo, Timothy Kettler, and Dennis McCallister at the University of Nebraska-Lincoln; Jim Ippolito Research Soil Scientist USDA-ARS-NWISRL, Kimberly, Idaho, formerly at Colorado State University; Ron Reuter at Oregon State University; Christoph Geiss at Trinity College-Connecticut; and William Zanner at the University of Minnesota. Development of this lesson was supported by the National Science Foundation Course, Curriculum, and Laboratory Improvement Program (NSF-CCLI), Award Number DUE-0042603. Any opinions, findings, conclusions or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of NSF.