The correct option is 2 and 3 only
Explanation
The lifecycle of a river is typically divided into three stages:
Youth, Mature, and Old. These stages are defined by the dominance of specific geomorphic processes (erosion vs. deposition) and the resulting landforms.
- Youth Stage: Dominance of vertical erosion (down-cutting).
- Mature Stage: Dominance of lateral erosion (widening) and the beginning of deposition.
- Old Stage: Dominance of deposition.
Statement-wise Analysis
- Statement 1 is Incorrect. Deep, narrow V-shaped valleys are the primary characteristic of the Youth Stage. In this stage, the river flows swiftly with high energy, leading to intense vertical down-cutting. In the Mature Stage, lateral erosion becomes significant, causing the valleys to widen significantly, transforming deep V-shapes into broader valleys.
- Statement 2 is Correct. During the Mature Stage, the integration of tributaries increases the volume of water. The river engages in lateral erosion, which widens the valley floor. This creates wider floodplains within which the trunk streams may flow in meanders.
- Statement 3 is Correct. Waterfalls and rapids are features of the Youth Stage, caused by irregular bed profiles and steep gradients. As the river enters the Mature Stage, it attains a graded profile (equilibrium), and irregularities like waterfalls and rapids disappear.
Key Takeaway
The
Mature Stage of a river is characterized by a shift from vertical erosion to
lateral erosion, leading to the disappearance of waterfalls, the widening of valleys, and the formation of floodplains with meanders.