Which of the following types of mass movements are categorized as rapid movements? 1. Creep 2. Mudflow 3. Solifluction 4. Slump Select the answer using the code given below.
- (a)1 and 2
- (b)1 and 3
- (c)2 and 4
- (d)3 and 4
Correct — C, 2 and 4. Mass movements are graded by how fast the material travels. Creep is the slowest of all — soil and rock inching downslope so gradually that it is read from tilted fence posts and bent tree trunks rather than watched. Solifluction is also slow: waterlogged soil sliding over frozen ground in periglacial areas, at centimetres a year. Mudflow is at the other end, a rapid flow of saturated debris that can run down a valley in minutes after heavy rain or an eruption. Slump is a landslide, in which a mass of rock or soil slips along a curved surface and rotates backwards — sudden and perceptible while it happens. So the two rapid ones are mudflow and slump.
- (a)1 and 2 — Pairs the slowest process with one of the fastest. Creep is measured in millimetres a year and is detected from its effects, not observed in motion.
- (b)1 and 3 — These are the two slow movements, exactly the opposite of what the question asks. Creep and solifluction are the standard examples of slow mass movement.
- (d)3 and 4 — Slump belongs, but solifluction does not. It is the slow downhill flow of water-saturated soil over frozen subsoil in periglacial regions.
Mass movement is the downslope transfer of material under gravity, without a transporting medium such as running water, ice or wind doing the carrying. The standard grouping is slow movements — creep and solifluction; rapid movements — earthflow, mudflow and debris avalanche; and landslides, which are rapid and perceptible, covering slump, debris slide, rock slide and rock fall. Water content is what usually decides where a movement sits on that scale.
Each of the four terms carries its speed in its description if you have seen it once. Creep is the one you infer from leaning poles; solifluction needs frozen ground below and so is a periglacial, seasonal process; mudflow needs saturation and moves in minutes; slump leaves a curved scar and a back-tilted block, which only forms in a sudden failure. The examiner has picked one from each end of the scale and mixed them, so the item is a straight sorting exercise.
- Mass movement transfers material downslope under gravity without a separate transporting medium.
- Slow movements: creep, at millimetres to centimetres a year, and solifluction over frozen subsoil.
- Rapid movements: earthflow, mudflow and debris avalanche.
- Landslides — slump, debris slide, rock slide and rock fall — are rapid and perceptible.
- A slump moves along a curved failure surface and leaves the block tilted backwards.
One from each end of the scale, alternated in the printed list — read the list before reading the options.
- Treating solifluction as rapid because it involves flowing saturated soil.
- Reading creep as a fast process because it shares a name with movement.
- Forgetting that landslides, though listed separately, are rapid movements.
A sorting item where the printed list alternates between the two categories being tested.
While travelling to a hilly region, you notice a massive boulder, which was loosened by heavy rains and moved downhill. This has resulted due to which of the following processes? 1. Mass wasting 2. Erosion 3. Weathering Select the correct answer using the code given below.
- (a) 1 only
- (b) 1 and 2 only
- (c) 2 and 3 only
- (d) 1, 2 and 3
Answer(d) 1, 2 and 3
The same family of processes with an official key behind it. It is worth noticing there that a single boulder moving downhill counts as mass wasting, erosion and weathering together — the categories overlap, which is why speed rather than mechanism is the sorting rule here.
- practice — not a real PYQ
Tilted fence posts, bent tree trunks and displaced retaining walls on a hillside are evidence of
- (a)soil creep
- (b)mudflow
- (c)rock fall
- (d)slump
Answer(a) soil creep — the movement is too slow to see, so it is read from its effects.
- practice — not a real PYQ
Solifluction is characteristically associated with which environment?
- (a)Arid deserts
- (b)Periglacial regions
- (c)Equatorial rainforests
- (d)Coral atolls
Answer(b) Periglacial regions — saturated soil flows slowly over frozen subsoil.