Q. Consider the following statements:
1. The phenomenon of wearing down of relief variations of the surface of the earth through erosion is known as gradation.
2. The earth’s surface is being continuously subjected to by external forces originating within the earth’s atmosphere and by internal forces from within the earth.
Which of the statements given above is/are NOT correct?

[A] 1 only

[B] 2 only

[C] Both 1 and 2

[D] Neither 1 nor 2

Answer: D
Notes:

The earth’s crust is dynamic. You are well aware that it has moved and moves vertically and horizontally. Of course, it moved a bit faster in the past than the rate at which it is moving now.  

  • The differences in the internal forces operating from within the earth which built up the crust have been responsible for the variations in the outer surface of the crust.  
  • The earth’s surface is being continuously subjected to external forces induced basically by energy (sunlight).  
  • Of course, the internal forces are still active though with different intensities. That means, the earth’s surface is being continuously subjected to by external forces originating within the earth’s atmosphere and by internal forces from within the earth.  
  • The external forces are known as exogenic forces and the internal forces are known as endogenic forces.  
  • The actions of exogenic forces result in wearing down (degradation) of relief/elevations and filling up (aggradation) of basins/ depressions, on the earth’s surface.  
  • The phenomenon of wearing down of relief variations of the surface of the earth through erosion is known as gradation. 

Source: NCERT – XI Fundamentals of Physical Geography