CHAPTER 8: FLUVIAL PROCESSES, PATTERNS AND LANDFORMS
The valley sideswill also be exposed toweathering andmassmovement.Mechanical and chemical weathering weaken the rock and soil on the valley sides. Rainfall and snowmelt may trigger landslides of material into the river making the valley even deeper. The depth of the V is controlled by a combination of several factors: • The speed of vertical erosion: in general fast rates of erosion lead to deeper valleys.
• The type of bedrock: hard rocks such as granite resist erosion, making more shallow valleys.
• Weathering and mass movement on the sides of the valley: These processes weaken and loosen the stones and soil on the sides of the valley. Scree and soil move downhill under the force of gravity and add to the river’s load, increasing its ability to erode and deepen its channel by abrasion.
Vertical erosion Weathering weakens sides of valley
Mass movement occurs on valley sides creating distinctive
V-shaped valley
Mass movement of material downhill into the river
Fig. 19 Exam Diagram: Formation of a V-shaped valley