BPSC 70th CCE Re-exam Prelims General Studies · Question 103 of 142

Correct — B, Tectonic. The Vale of Kashmir is a structural basin, not a valley cut by a river. It was produced by folding and faulting as the Himalayan chain was thrust up between the Indian subcontinent and the rest of Asia: the Pir Panjal rose on the south-west, the Greater Himalayan range on the north-east, and the trough between them subsided. The result is an oval basin about 135 km long and 32 km wide, roughly 4,865 sq km in area, lying at an average elevation of about 1,850 m, running north-west to south-east along the strike of the mountain chain — the giveaway, because an erosional valley follows the gradient of its river, while this one follows the grain of the orogeny. The Jhelum drains it and then has to saw its way out through the Pir Panjal at the Baramulla gap, which is what a river does when it is younger than the structure it sits in. The floor of the basin was for a long period occupied by a lake, and the lake's sediments now form the karewas — flat-topped, plateau-like terraces of lake-laid silt and clay that mantle the valley floor and its flanks, and on which the saffron of Pampore is grown. A lacustrine fill of that kind is only possible in a closed structural depression, which is a second, independent argument for the same answer. So the Kashmir Valley is classified as a tectonic (structural, intermontane) valley: the mountains made the hollow, and water merely filled and later drained it.

• (a)Erosional — An erosional valley is carved out by running water or ice, and takes a V-shape from a river or a U-shape from a glacier. The Kashmir basin has neither profile; it is a broad flat-floored trough far wider than the Jhelum could ever have cut, and its long axis follows the mountain structure rather than the river's course. The Jhelum inherited the basin; it did not make it.
• (c)Blind — A blind valley is a karst landform: a surface stream flows down a limestone valley and then disappears underground into a swallow hole, so the valley simply ends against a rock wall with no outlet. Nothing of the sort applies here — the Kashmir Valley has a perfectly ordinary surface outlet, the Jhelum, through the Baramulla gap.
• (d)Rift — The sharpest distractor, because a rift valley is also tectonic — but of a specific kind, a graben where a block has dropped between two parallel normal faults under extension. The Kashmir basin formed under compression, by folding and faulting during mountain building. India's textbook rift valleys are the Narmada, the Tapi and the Damodar; Kashmir is not among them, and a candidate who treats 'tectonic' and 'rift' as synonyms will pick this option.

Valleys are classified by what made them. Erosional valleys are cut by an agent — rivers give V-shaped valleys and gorges, glaciers give U-shaped troughs and hanging valleys, and both are the work of removal. Structural or tectonic valleys are made by earth movement instead: the ground is folded down into a syncline or dropped along faults, and the depression exists before any river arrives. Within the tectonic family, a rift valley or graben is the extensional case, where a block subsides between two parallel normal faults, as in the East African Rift and the Narmada trough. An intermontane basin is the compressional case, a trough left between rising ranges during mountain building, and that is what the Vale of Kashmir is. A blind valley belongs to a third family altogether, the karst landforms produced by the solution of limestone, alongside sinkholes, poljes, caverns and stalactites. Recognising which family a named landform belongs to is the whole skill being tested.

The reasoning route is to ask what the landform's shape and dimensions imply about its origin. A basin 135 km long and 32 km wide, flat-floored, ringed by mountains and filled with lake sediments cannot have been excavated by the stream that now drains it — the discriminator is size and shape against the competence of the river. Then narrow within the tectonic family: does the setting suggest pulling apart or pushing together? The Himalaya is the world's type example of continental collision, therefore compression, therefore not a rift. The Kashmir case is worth learning as a package because it recurs from several directions: the Karewa deposits (lake sediments, saffron soils), the Jhelum's exit at Baramulla, the enclosing Pir Panjal with the Banihal pass at 2,832 m and the Pir Panjal pass at 3,494 m, and the old tradition that the valley was once the lake Satisar. Each of those can be the hook for a question, and each points back to the same structural origin.

• The Kashmir Valley is about 135 km long and 32 km wide, covers roughly 4,865 sq km, and lies at an average elevation of about 1,850 m, bounded by the Pir Panjal on the south-west and the Greater Himalaya on the north-east
• Geologists describe it as a structural basin: 'the valley of Kashmir was formed by folding and faulting as the Himalayan mountain chain was thrust between the Indian subcontinent and the rest of Asia'
• The Jhelum drains the valley and cuts through the Pir Panjal at the Baramulla gap; the valley is reached from the Punjab plain by the Pir Panjal pass (3,494 m) and the Banihal pass (2,832 m)
• Karewas — flat-topped terraces of lake-laid deposits left by the water body that once filled the basin — cover much of the valley floor and its flanks, and carry the saffron fields of Pampore
• India's classic rift (graben) valleys are those of the Narmada, the Tapi and the Damodar, all formed by faulting and down-warping — a different tectonic mechanism from the Kashmir basin

• Treating 'tectonic' and 'rift' as the same thing — every rift valley is tectonic, but not every tectonic valley is a rift
• Assuming any large valley must have been cut by its river; in an intermontane basin the depression comes first and the river is a later occupant
• Confusing a blind valley (karst, stream sinks underground) with a hanging valley (glacial, tributary trough left above the main trough)

BPSC asks the classification directly — name the type of valley, the type of coast, the type of rock — and expects a one-word taxonomy answer, which is why definitions have to be crisp. UPSC prefers to test the same taxonomy through consequences: why the Narmada flows west, why a particular river has a rift valley, why a coast has offshore island chains. Learn the definition for BPSC and the mechanism for UPSC, and one set of notes serves both.

• practice — not a real PYQ

  Which one of the following Indian rivers flows through a rift valley ?

  • (a)Mahanadi
  • (b)Narmada
  • (c)Kaveri
  • (d)Sone

  Answer(b) Narmada — it occupies a linear rift valley between the Vindhya and Satpura ranges, which is why it flows west while most large peninsular rivers flow east.

• practice — not a real PYQ

  The Karewa formations of the Kashmir Valley are deposits of

  • (a)glacial moraine
  • (b)volcanic ash
  • (c)an ancient lake
  • (d)wind-blown loess

  Answer(c) an ancient lake — the karewas are lacustrine silts and clays laid down when the structural basin held a lake, and they now form the flat terraces on which Kashmir's saffron is grown.