If the movement of the earth's crust or a major climatic change makes an old stream young, it is called

The process where an old stream regains youthful characteristics due to tectonic uplift or climatic changes is known as rejuvenation [c1][t2]. Rejuvenation, literally meaning 'being young again,' occurs when a negative movement (land uplift or sea-level fall) steepens the river's gradient, renewing its capacity for active vertical incision and down-cutting [c1][t3]. This process can be triggered by tectonic forces (dynamic rejuvenation), changes in sea level (eustatic rejuvenation), or climatic shifts that alter the river's discharge or sediment load [t1][t2]. In contrast, a consequent stream follows the initial slope of the land [c4], a subsequent stream develops along belts of less resistant rock [c3], and aggradation refers to the deposition of sediment that builds up the river bed [t1]. Rejuvenation effectively restarts the cycle of erosion, creating landforms like river terraces and knickpoints [c1][t2].

Sources

1. [1] Certificate Physical and Human Geography , GC Leong (Oxford University press 3rd ed.) > Chapter 5: Landforms made by Running Water > River Rejuvenation > p. 55
2. [2] https://en.wikipedia.org/wiki/River_rejuvenation
3. [3] https://www.nature.com/articles/s44304-025-00106-2
4. [4] https://ebooks.inflibnet.ac.in/geop11/chapter/interruptions-of-the-cycle-of-erosion-tectonics-climatic-and-base-level-changes/
5. [5] Certificate Physical and Human Geography , GC Leong (Oxford University press 3rd ed.) > Chapter 5: Landforms made by Running Water > The Development of a River System > p. 47
6. [6] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 16: Fluvial Landforms and Cycle of Erosion > Subsequent Rivers > p. 210