Which of the following statements about rockslide is correct?

Correct — D. NCERT's Class XI Fundamentals of Physical Geography defines rockslide as the sliding of individual rock masses down bedding, joint or fault surfaces.

It then separates it from rock fall. Rock falls occur from the superficial layers of the rock face, which distinguishes them from rockslide, which affects materials up to a substantial depth. That is option (d).

Why the others are wrong

• (a)
  It affects only the outermost layer of the rock face — That is rock fall, not rockslide. NCERT says rock falls occur from the superficial layers of the rock face, and uses exactly that to set them apart from rockslide.
• (b)
  It is slower than rock fall — NCERT sets no such speed ranking. It calls rock sliding over steep slopes very fast and destructive, and the difference it draws from rock fall is depth, not speed.
• (c)
  It involves backward rotation of debris — Backward rotation defines a slump, the slipping of rock debris with a backward rotation relative to the slope. A debris slide, NCERT adds, moves without that rotation.

NCERT describes landslides as relatively rapid and perceptible movements of relatively dry material, and names their kinds by how the mass moves.

Slump: slipping of rock debris with a backward rotation.
Debris slide: rapid rolling or sliding of earth debris without that rotation.
Rockslide: rock masses sliding down bedding, joint or fault surfaces.
Rock fall: rock blocks falling free, clear of the slope.

Key facts

• Rockslide is the sliding of individual rock masses down bedding, joint or fault surfaces (NCERT Class XI, Geomorphic Processes).
• Rock falls occur from the superficial layers of the rock face, while rockslide affects materials up to a substantial depth.
• Slump is the slipping of rock debris with a backward rotation with respect to the slope.
• Mass movements are aided by gravity, with no geomorphic agent such as running water, glaciers or wind taking part.

Common traps

• Swapping rockslide and rock fall: the fall comes off the surface layers, the slide cuts deep.
• Pinning backward rotation on any slide, when NCERT reserves it for slump.

No directly related past PYQ was found.