UPHESC Assistant Professor Geology PYQs

Concept: Compression shortens and thickens the crust through folding and thrust (reverse) faulting, as in fold-and-thrust belts like the Himalaya.

1. Normal faulting – crustal extension (lengthening).
2. Strike-slip faulting – horizontal displacement with no net shortening.
3. Metamorphism is a change in mineralogy/texture, not a shortening mechanism.

Short trick: Squeeze → folds + thrusts; Stretch → normal faults.

Concept: Poisson's ratio ν = lateral strain / longitudinal strain (dimensionless; about 0.25 for most rocks, 0.5 for incompressible fluids).

1. Young's modulus E = longitudinal stress / longitudinal strain.
2. Bulk modulus K = pressure / volumetric strain.
3. Rigidity (shear) modulus G = shear stress / shear strain.

Short trick: Poisson = sideways ÷ lengthwise strain.

Concept: Each stage of the fluvial cycle has typical landforms.

1. Initial stage – vigorous down-cutting into bedrock by eddies with pebbles: pot holes → (3).
2. Youth – deep V-shaped valleys, gorges → (2).
3. Mature – where the river leaves the mountains onto the plains, its load spreads as alluvial fans → (1).
4. Old stage – broad flood plains, meanders, ox-bow lakes → (4). Code 3-2-1-4.

Short trick: Pothole → V-valley → fan → flood plain (mountain to plain).

Concept: After the elastic straight line (1) and the yield point, the curve can follow three paths: horizontal (3) = ideal plastic flow, rising (4) = strain hardening (more stress needed for more strain), falling (2) = strain softening (stress needed drops as strain increases).

1. Sector 2 slopes downward beyond yield – the rock weakens with continued strain → strain softening.
2. Sector 1 – elastic; sector 3 – perfectly plastic; sector 4 – strain hardening.

Short trick: After yield: up = hardening, flat = plastic, down = softening.

Concept: Driven by the trade winds and westerlies and deflected to the right by the Coriolis force, the major subtropical ocean gyres circulate clockwise in the Northern Hemisphere and anticlockwise in the Southern Hemisphere.

1. N. Atlantic gyre: Gulf Stream → N. Atlantic Drift → Canary → N. Equatorial current (clockwise).
2. N. Pacific: Kuroshio → N. Pacific → California → N. Equatorial (clockwise).

Short trick: North – Coriolis to the right – clockwise gyres.

Concept: Barrier reefs, separated from the coast by a wide, deep lagoon, are the largest, highest and most extensive of all reef types; the Great Barrier Reef of Australia extends ~2300 km.

1. Fringing reefs – narrow reefs attached to the shore; most common but small.
2. Atolls – ring-shaped reefs around a lagoon, no central island (e.g. Lakshadweep).

Short trick: Great Barrier Reef = the biggest reef = barrier type.

Concept: Thermohaline ('thermo' = heat, 'haline' = salt) circulation is the global deep-ocean 'conveyor belt' driven by density differences caused by temperature and salinity.

1. Cold, salty water sinks in the North Atlantic and around Antarctica, flows along the deep ocean and upwells elsewhere.
2. Surface currents are mainly wind-driven, not thermohaline.

Short trick: Thermo + haline = temperature + salt → density-driven deep currents.

Concept: Fine terrigenous (wind- and current-borne) clay settles on the abyssal floor extremely slowly – of the order of 1–2 mm per 1000 years (pelagic red/brown clay).

1. Biogenic oozes accumulate faster, ~1–3 cm/1000 yr.
2. mm/year rates are typical of continental shelves, deltas and lakes – far too fast for the deep ocean.

Short trick: Deep-sea clay: about a millimetre per millennium.

Concept: A broad belt of siliceous diatom ooze encircles Antarctica (Southern Ocean) and also occurs in the high-latitude North Pacific, where cold, nutrient-rich upwelling waters support diatom blooms.

1. Radiolarian ooze – mainly the equatorial Pacific.
2. Carbonate (Globigerina) ooze – warm, shallower (above CCD) floors of the Atlantic; carbonate dissolves in cold Antarctic waters.

Short trick: Diatoms – cold poles; Radiolaria – equator; Globigerina – warm, above CCD.

Concept: In a confined aquifer, water in a well rises to the piezometric (potentiometric) surface; where this surface lies above ground level, water flows out at the surface without pumping – a flowing artesian well.

1. If the piezometric surface is above the aquifer top but below ground → non-flowing artesian well.
2. Classic example: Great Artesian Basin, Australia.

Short trick: Piezometric surface above ground = free-flowing artesian well.