4. How does jointing (or joint density) influence weathering? 5. Which of the following does NOT physically loosen rocks on the surface? (Hint: which is not a physical weathering process) 6. Mechanical weathering is breaking big pieces into smaller fragments, producing sediments prone to erosion. A boiling pot of soup illustrates the chemical breakdown of materials. In nature the process is slower, but similar. Erosion, the transport of sediment, continues the processes of both chemical and mechanical weathering. Weathering – Physical breakdown and chemical alteration of rock at Earth’s surface 2 kinds of Weathering – mechanical and chemical Mechanical Weathering • Mechanical weathering – breaking of rocks into smaller pieces 1) Frost Wedging 2) Abrasion 3) Plant/Animal Activity 4) Gravity/Pressure 5) Wetting/Drying 6) Exfoliation / Joint Sheeting Some effects of weathering on joints in granitic rocks Judy Ehlen* US Army Engineer Research and Development Center, Topographic Engineering Center, Alexandria, VA 22315-3864, USA Abstract Standard engineering weathering classifications, most of which are based on weathered granite, feldspar reacted with water to make clay What happened to the quartz?