ASBOG Practice Exam

What occurs when the dip downstream is less than the slope of the valley regarding the direction of the V?

1. It points directly downhill

2. It points upstream within the contours of the topography

3. It becomes nonexistent

4. It points to the sides of the valley

The correct answer is: It points upstream within the contours of the topography

When the dip downstream is less than the slope of the valley, the V-shape formed by the contour lines actually points upstream. This phenomenon occurs due to the interaction between geological structures and topographical relief. The V forms where the river or stream cuts through a valley, and the apex of the V typically aligns with the direction of the dip of the underlying rock layers. In this scenario, where the dip is less steep than the valley slope, the geological layers are tilted at a gentler angle compared to the steepness of the valley walls. As a result, the stream or river has eroded the valley in such a way that it accentuates the underlying dip of the rock layers, leading to the V pointing upstream—essentially indicating that the water flows in the opposite direction to how the geological bedding is inclined. Other options, such as the V pointing directly downhill, suggesting it becomes nonexistent, or pointing to the sides of the valley, do not accurately describe the relationship between the dip and the valley's slope in this context. When analyzing topographic maps and geological formations, recognizing how these relationships affect the geometry of features is crucial for understanding hydrology and rock structure interactions.