Q. Consider the following statements:
1. Large and deep holes at the base of waterfalls are formed due to sheer impact of water and rotations of boulders are called as plunge pools.
2. Over the rocky beds of hill-streams more or less circular depressions form because of stream erosion aided by the abrasion of rock fragments are called as potholes.
Which of the statements given above is/are correct?

[A] 1 only

[B] 2 only

[C] Both 1 and 2

[D] Neither 1 nor 2

Answer: C
Notes:

Over the rocky beds of hill-streams more or less circular depressions called potholes form because of stream erosion aided by the abrasion of rock fragments.  

  • Once a small and shallow depression forms, pebbles and boulders get collected in those depressions and get rotated by flowing water and consequently the depressions grow in dimensions.  
  • A series of such depressions eventually join and the stream valley gets deepened.  
  • At the foot of waterfalls also, large potholes, quite deep and wide, form because of the sheer impact of water and rotation of boulders.  
  • Such large and deep holes at the base of waterfalls are called plunge pools. 

Source: NCERT – XI Fundamentals of Physical Geography