This page provides a brief outline of, lists the main points of, gives links to figures for, and lists the assigned reading for a lecture in Dr. Bruce Railsback's GEOL 1121 class at the University of Georgia. This page is not intended as a set of lecture notes, and it cannot subsititute for a set of lecture notes. Familiarity with this page alone will not assure satisfactory grades on exams in the course.

Lecture 20 (Friday, March 8, 2002): Mechanical Weathering

Brief outline of this lecture:
Mechanical weathering
     Root wedging

Main points of this lecture:
Weathering occurs because rocsk are exposed to conditions unlike those in which they formed.
Mechanical weathering breaks rocks into smaller pieces.
Mechanical weathering can be divided into three processes.
Mechanical weathering generates more surface area on which chemical weathering can work and conduits through which water can move.

Figures used in this lecture:
Basics of Weathering
Basics of mechanical weathering
Mechanical Weathering Step I
Mechanical Weathering Step II - Exfoliation
Mechanical Weathering Step III - Freeze-thaw and root wedging
Mechanical Weathering IIIa - Freeze-thaw in detail
Mechanical Weathering Step IV - more mechanical weathering
Mechanical Weathering Step V - more mechanical weathering
Mechanical Weathering Step VI - more mechanical weathering
Particle size and surface area

Reading assignment: Page 251.

Next Lecture
Email to Railsback (
Railsback's main 1121 web page
Railsback's main web page
UGA Geology Department web page