Match the following :
Types of Plateau
(a) Intermont Plateau
(b) Piedmont Plateau
(c) Lava Plateau
(d) Glacier Erosion Plateau
Example of Plateau
(i) Colorado Plateau
(ii) Colombia Plateau
(iii) Green

Question

Match the following :
Types of Plateau
(a) Intermont Plateau
(b) Piedmont Plateau
(c) Lava Plateau
(d) Glacier Erosion Plateau
Example of Plateau
(i) Colorado Plateau
(ii) Colombia Plateau
(iii) Greenland Plateau
(iv) Baluchisthan Plateau

UnlockIAS · Accepted Answer

Correct — option (3), which reads (a) - (iv), (b) - (i), (c) - (ii), (d) - (iii). Plateaus in this classification are named for how they were made, not for where they are, so each item in the first column is a mode of origin and the second column has to be read for the origin each example records. Three of the four pairs can be settled independently, and once they are settled the fourth is forced. Start with the Lava Plateau at (c). The Columbia Plateau — printed here as 'Colombia Plateau' — lies between the Cascade Range and the Rocky Mountains in Washington, Oregon and Idaho and is a flood-basalt plateau: successive fissure eruptions of the Columbia River Basalt Group in the late Miocene and early Pliocene piled lava to more than 1.8 km in places over some 63,000 square miles, drowning the older relief and leaving a broad, slightly sagging basalt surface. Nothing else in the second column was built by lava, so (c) takes (ii). Next the Glacier Erosion Plateau at (d). Greenland is the only entry that carries an ice sheet, and an ice-scoured plateau is by definition the work of moving ice, so (d) takes (iii). Then the Intermont Plateau at (a) — a plateau enclosed within or shut in by mountain ranges. Balochistan, printed 'Baluchisthan', is described as an extensive plateau of rough terrain divided into basins by ranges of significant height and ruggedness, sitting on the south-eastern edge of the Iranian plateau; that is exactly the intermontane setting, so (a) takes (iv). Three slots in the second column are now spent, and only the Colorado Plateau at (i) is left, so the Piedmont Plateau at (b) must take it — a piedmont plateau being one that lies at the foot of a mountain range, and the Colorado Plateau does lie against the flank of the Rocky Mountains on its eastern and northern sides. That completes (a) - (iv), (b) - (i), (c) - (ii), (d) - (iii), which is option (3).

Why the other options are wrong — (a) This row pairs the Lava Plateau with Greenland and the Glacier Erosion Plateau with Balochistan, and both are impossible. Greenland's plateau surface is the product of ice, not of fissure eruptions; there is no flood-basalt province beneath the ice sheet that gives the island its plateau form, and the item is in the list precisely because it is the ice example. Balochistan, at the other end, is a dry sub-tropical plateau on the edge of the Iranian plateau with no ice sheet and no record of Pleistocene ice-sheet scouring of the kind that shapes a glacier-erosion plateau. The row also gives the Intermont Plateau to Colorado, which is the one pair a candidate might argue for, and that is what makes the row attractive; but the two impossible pairs at (c) and (d) kill it before that argument is worth having.  (b) Here the Intermont Plateau is given to Greenland and the Glacier Erosion Plateau to Balochistan, so the row inverts the single most obvious pair in the question. Greenland is not shut in by mountain ranges — its plateau is an ice sheet resting in a bedrock basin rimmed by coastal highlands, and it is in this list as the ice example. Balochistan carries no ice. The row further hands the Lava Plateau to Colorado, whose surface is a thick, largely undeformed pile of sedimentary rock — sandstone, shale and limestone into which the Colorado river has cut the Grand Canyon — not a basalt sheet. The habit that disposes of this row in seconds is to find the one example that can belong to only one category, which here is Greenland, and to strike out every row that spends it elsewhere.  (d) This is the near-miss, and it is the row worth studying. It gets the two anchors right — Intermont with Balochistan and Glacier Erosion with Greenland — and then swaps the remaining two, giving the Piedmont Plateau to Columbia and the Lava Plateau to Colorado. That swap is the error. The Columbia Plateau is the textbook flood-basalt plateau of North America, built by the Columbia River Basalt Group, while the Colorado Plateau is a thick, stable block of layered sedimentary rock that was uplifted rather than erupted. A candidate who verifies only the pairs that are easy will accept this row, which is precisely how it is built: a setter who leaves the easy pairs intact has done so deliberately. In a paper that deducts a quarter of a question's marks for a wrong answer, checking the last two pairs is worth the few seconds it costs.

Concept: Plateaus are elevated tablelands with a comparatively level top and at least one steep side, and geography classifies them by how they came to be. An intermontane plateau is enclosed by, or lies between, mountain ranges — Tibet between the Himalaya and the Kunlun is the largest, and the Bolivian altiplano and Balochistan belong to the same family; these are usually the highest and most extensive plateaus because they were lifted with the ranges that hem them in. A piedmont plateau lies at the foot of a mountain range, with a plain or a sea on its other flank, the name coming from the Latin for foot and mountain. A continental or tableland plateau rises abruptly from a lowland or a coast, as the Deccan and the Chota Nagpur plateaus do. A lava or volcanic plateau is built up rather than uplifted: fissure eruptions of low-viscosity basalt spread in sheet after sheet until the older relief is buried, which is how the Columbia Plateau in the United States and the Deccan Traps in India were made. A glacier-erosion plateau is a surface planed and scoured by an ice sheet, of which Greenland and Antarctica are the standard examples. Two further terms are worth carrying: a dissected plateau is one that streams have cut into a maze of valleys and residual flat tops, and a continental shield is an ancient plateau of crystalline rock worn low over geological time.

State PCS 2021 Q21 — Geography PYQ with Answer

State PCS 2021 Q21 — Geography PYQ with Answer