MPSC 2022 Prelims Paper-I · Question 14 of 100

Correct — option (3). Column I names four types of plateau and Column II four Indian plateaus, and the columns are printed side by side only because the page is set that way; the pairing has to be built. Build it from the one pairing that admits of no argument. The volcanic plateau at (b) can only be the Deccan at (i): the Deccan plateau is built of horizontal sheets of basalt poured out in the great eruptions of the late Cretaceous, the flows known as the Deccan Traps, and no other plateau in this list is of volcanic origin at all. That single pairing decides the question, because option (3) is the only row that makes it, and it is worth noticing that a candidate who is unsure of the other three can still answer the item with complete confidence on this one. The remaining pairings follow. The step-like plateau at (c) goes to the Vindhya at (ii), whose horizontally bedded Vindhyan sandstones weather back into a succession of terraces and scarps between the Ganga plain and the Narmada-Son trough. The dome-shaped plateau at (a) goes to the Chota Nagpur at (iii), whose surface is arched up in the middle, the land falling away in steps on every side from the higher pat surfaces of the interior. The piedmont plateau at (d) goes to the Shillong plateau at (iv); a piedmont plateau is by definition one lying at the foot of a mountain range, and the classification this paper follows places the Shillong plateau, which stands beyond the Brahmaputra valley below the eastern Himalayan front, in that class. The completed pairing is (a)-(iii), (b)-(i), (c)-(ii), (d)-(iv), which is option (3).

• (1)(a) - (i), (b) - (iii), (c) - (iv), (d) - (ii) — This row gives the volcanic plateau to Chota Nagpur, and that is enough to end it. The Chota Nagpur plateau is part of the ancient crystalline shield of the peninsula — granites, gneisses and the folded rocks of the Dharwar and Gondwana systems, which is why it carries the country's greatest concentration of coal, iron ore, mica and bauxite — and it has no relation to the lava flows of the Deccan. The row then gives the dome-shaped description to the Deccan and the step-like one to Shillong. Its usefulness for revision is that it shows how quickly a matching item collapses when the least ambiguous clue is tested first: volcanic can belong to exactly one Indian plateau, so any row that spends that clue elsewhere is finished before the other three pairs are read.
• (2)(a) - (ii), (b) - (iv), (c) - (iii), (d) - (i) — This row gives the volcanic plateau to Shillong and the dome-shaped one to the Vindhya, and neither can stand. The Shillong or Meghalaya plateau is a detached block of the peninsular shield, separated from the main mass by the gap in which the Ganga and Brahmaputra flow, and it is built of the same ancient crystalline rocks; it carries the Garo, Khasi and Jaintia hills, with Mawsynram and Cherrapunji on the steep southern slopes that face the monsoon. Nothing in it is volcanic. The Vindhya, for its part, is a sequence of horizontally bedded sandstones and limestones, and horizontal beds erode into steps and scarps rather than into a dome. The row inverts almost every relation in the question and can be discarded on the Deccan pairing alone.
• (4)(a) - (iv), (b) - (ii), (c) - (i), (d) - (iii) — This row gives the volcanic plateau to the Vindhya, which reverses the two central pairings of the question, and it is the row a candidate is likeliest to reach if he has learnt that the Deccan has a step-like appearance. That is not wrong as a description — the Deccan Traps take their name from a word meaning step, because the successive lava flows weather back into a staircase profile — but a matching item allows each clue to be used once, and volcanic can belong to no Indian plateau except the Deccan while step-like can also describe the terraced Vindhyan sandstones. When two clues could both fit one item, give it the clue that fits it uniquely and let the other clue go to the item that can still take it. This row also gives the piedmont description to Chota Nagpur and the dome to Shillong.

Plateaus are classified in two ways and Indian examples are used for both. The first classification is by origin. A volcanic or lava plateau is built by successive flows of fluid basalt spreading over the surface, of which the Deccan is the Indian instance and the Columbia plateau of the United States the foreign one. An intermontane plateau lies enclosed within mountain ranges, as Tibet does between the Himalaya and the Kunlun. A piedmont plateau lies at the foot of a mountain range, the name meaning exactly that, with the Piedmont plateau of the eastern United States below the Appalachians and the Patagonian plateau below the Andes as the standard examples. A continental or tableland plateau rises directly from the plains or the sea. The second classification is by form, and it is the one from which the dome-shaped and step-like descriptions come: an upwarped block whose surface arches in the middle is called dome-shaped, while horizontally bedded sedimentary rock eroded into terraces and scarps gives a step-like profile. The Indian peninsular plateau, the oldest and most stable landmass in the country, contains examples of several of these at once — the lava-covered Deccan in the west and centre, the sandstone country of the Vindhya and Bundelkhand to the north, the mineral-bearing Chota Nagpur block to the east, and the detached Shillong plateau beyond the Ganga and Brahmaputra gap.

Physiography of India is examined every year in MPSC papers, and plateaus are set either as a match of this kind or as one-line questions about the rocks, minerals or rivers of a named plateau. The value of this particular item is in the method it rewards rather than in the four pairs it contains. Two of the pairings, the dome-shaped and the piedmont, rest on descriptive classifications that different textbooks apply with different degrees of strictness, and a candidate who tries to settle them first will spend minutes and gain nothing. One pairing is beyond dispute — the Deccan is the country's volcanic plateau — and testing it first identifies the answer outright. That is the general shape of a well-set matching question: it contains at least one clue that can belong to only one item, and the whole exercise is to find that clue before working through the rest. The second point worth taking from this item is the tie-break rule it illustrates. When one item could answer to two descriptions, as the Deccan could to both volcanic and step-like, assign the description that fits it uniquely and let the other go to the item that can still take it.

• The Deccan plateau is India's volcanic plateau, built of horizontal basalt flows erupted in the late Cretaceous and known as the Deccan Traps; the word trap comes from a Scandinavian word for step, after the staircase profile the flows weather into.
• The Vindhya plateau is formed of horizontally bedded Vindhyan sandstones and limestones lying between the Ganga plain and the Narmada-Son trough, and their erosion into terraces and scarps gives the step-like form.
• The Chota Nagpur plateau, spread over Jharkhand and parts of Chhattisgarh, West Bengal and Odisha, is an upwarped block of the ancient shield carrying coal, iron ore, mica and bauxite, and its arched surface gives it the dome-shaped description.
• The Shillong or Meghalaya plateau is a detached block of the peninsular shield beyond the Ganga and Brahmaputra gap; it carries the Garo, Khasi and Jaintia hills, with Mawsynram and Cherrapunji on its southern slopes.
• A piedmont plateau is by definition one lying at the foot of a mountain range, the standard examples being the Piedmont plateau below the Appalachians and the Patagonian plateau below the Andes.

• Trying to settle the descriptive pairings first, when one pairing in the question is beyond dispute and identifies the answer by itself
• Giving the step-like description to the Deccan because the Traps do weather into steps, when volcanic is the clue that belongs to the Deccan uniquely
• Supposing that the Shillong plateau is volcanic or that Chota Nagpur is, when both are blocks of the ancient crystalline shield
• Reading two side-by-side columns as though the printing paired them, when in a matching question the adjacency is layout and asserts nothing

Plateaus reach MPSC papers as matching items of this kind, as one-line questions asking which state a named plateau lies in or which rocks or minerals it carries, and as statement questions on the peninsular plateau as a whole. The Commission returns most often to the Deccan, because it links to the Traps, to black soil and to the cotton belt, and to Chota Nagpur, because it links to minerals and industry. The classification by origin is tested with foreign examples as well, so Tibet for the intermontane type and Patagonia for the piedmont type are worth holding alongside the Indian ones. A compact preparation is a list of the Indian plateaus with their states, rocks, minerals and rivers, and a second short list of the four origin types with two examples each.

No directly related past PYQ was found.

• practice — not a real PYQ

  The Deccan plateau is classified as a volcanic plateau because

  • (a)it lies at the foot of the Western Ghats
  • (b)it is built of successive horizontal flows of basalt lava
  • (c)it is enclosed between two mountain ranges
  • (d)its surface is arched upward in the middle

  Answer(b) It is built of successive horizontal flows of basalt lava — the Deccan Traps, erupted in the late Cretaceous, cover a great part of western and central India and weather into the staircase profile that gives them their name. A plateau at the foot of a range is piedmont, one enclosed between ranges is intermontane, and one arched up in the middle is described as dome-shaped, so each of the other options names a different class.

• practice — not a real PYQ

  Which of the following plateaus is separated from the main peninsular block by the gap through which the Ganga and the Brahmaputra flow ?

  • (a)The Malwa plateau
  • (b)The Chota Nagpur plateau
  • (c)The Shillong plateau
  • (d)The Bundelkhand plateau

  Answer(c) The Shillong plateau — geologically it is a detached fragment of the peninsular shield, cut off from the main mass by the gap in which the two great rivers flow, and it carries the Garo, Khasi and Jaintia hills with Mawsynram and Cherrapunji on its steep southern face. Malwa, Bundelkhand and Chota Nagpur all belong to the continuous peninsular block itself.