Which process is responsible for the formation of V-shaped valleys?

V-shaped valleys are formed by fluvial erosion, where fast-flowing rivers or streams in their upper course cut vertically into the landscape. This process, known as downcutting, carves a deep, narrow channel. Simultaneously, weathering and mass wasting processes (like soil creep and landslides) cause the steep valley walls to collapse and move downslope toward the river channel. The combination of vertical erosion by the water and the slumping of the valley sides results in the characteristic V-shaped cross-section. This landform is typically found in mountainous or upland areas where river gradients are steep.

B. Erosion caused by ocean waves: This process erodes coastlines, creating features such as sea cliffs, wave-cut platforms, and sea stacks, not inland V-shaped valleys.

C. Erosion caused by ground water: Groundwater erosion primarily occurs underground through chemical dissolution, forming features like caves, caverns, and sinkholes (karst topography).

D. Erosion caused by wind: Wind (aeolian) erosion is most significant in arid environments, sculpting features like sand dunes, yardangs, and desert pavement, but it does not carve deep valleys.

1. Earle, S. (2019). Physical Geology (2nd ed.). BCcampus. Chapter 13.2, "Stream Erosion and Deposition." Retrieved from https://opentextbc.ca/physicalgeology2ed/chapter/13-2-stream-erosion-and-deposition/. The text states, "Streams carve their own valleys... In the steep, upper course of a stream, the valley is typically a V-shape."

2. Johnson, C., Affolter, M. D., Inkenbrandt, P., & Mosher, C. (2017). An Introduction to Geology. Salt Lake Community College. Chapter 11.2.1, "Erosional and Depositional Landforms." Retrieved from https://opengeology.org/textbook/11-streams-floods/. This source explains, "Stream erosion will cut a V-shaped valley... The V-shape is created by the stream undercutting the valley walls, which causes mass wasting of the slopes."

3. U.S. Geological Survey (USGS). (n.d.). Geologic Formations. "Valleys." The USGS explains that river erosion is the primary force in carving valleys, with the shape (such as a V-shape) being determined by the erosional agent and the rock type. V-shapes are explicitly linked to river erosion in young, steep landscapes.