1. From Snow to Moving Glacier Ice and Terrain-Scale Glacier Types

Snow does not turn into a glacier overnight. Fresh, fluffy snowfall is mostly air (density ~50–100 kg/m³). Where snow survives summer warmth, burial beneath subsequent snowfalls snaps delicate crystal tips, packs grains into rounded pellets, and expels air through partial melting and refreezing—producing an intermediate granular material called firn (or névé, density ~400–830 kg/m³). Continued overburden compression eventually seals off interconnecting air passages into isolated gas bubbles, creating true crystalline glacier ice (~830–917 kg/m³). Depending on snowfall rate and temperature, that transformation takes just a few years in wet maritime mountains (like coastal Alaska or Patagonia) to centuries on the frigid, dry East Antarctic Plateau.

Keep the definition exact for Prelims: a snowfield is a perennial patch of snow/firn too thin to deform and flow, while sea ice (frozen ocean water) and frozen lake ice float on water rather than accumulating on land. A glacier is strictly a perennial body of land-formed ice thick enough to deform and move under its own weight due to gravity.

1.1 Glacier Forms Classified by Terrain Control and Scale

Glaciers assume different geometries according to underlying topography and scale—categories of physical setting, never compulsory life stages through which one glacier evolves:

• Cirque (Corrie) & Valley Glaciers (Constrained by Topography): A small cirque glacier occupies a high armchair-shaped mountain hollow; when ice spills down-valley between rock walls like a frozen river, it forms a valley (alpine) glacier (e.g., Gangotri in Garhwal, Bara Shigri in Himachal, Zemu in Sikkim).
• Piedmont Glaciers & Ice Fields: Where one or more steep valley glaciers exit narrow mountain gorges onto a flat coastal or foreland plain, ice spreads laterally into a broad bulb-shaped lobe—a piedmont glacier (famously Alaska's Malaspina Glacier). Higher in mountain ranges, interconnected basins of ice burying valleys while high peaks still poke through and steer flow form an ice field (such as the Patagonian or Karakoram Biafo–Hispar ice networks).
• Ice Caps & Continental Ice Sheets (Unconstrained by Underlying Relief): An ice cap (<50,000 km², such as Iceland's Vatnajökull) forms a dome burying a highland plateau and flowing radially outward from its thick centre. At continental scale (>50,000 km²), an ice sheet buries entire mountain ranges under 2–4 kilometres of ice—today preserved only in Antarctica and Greenland. Any glacier whose front terminates in the ocean is termed a tidewater glacier, highlighting rapid ice loss by iceberg calving.

2. Mass Balance, Equilibrium Line, Ice Motion, and Terminus Retreat

Every glacier runs an annual mass budget comparing inputs and outputs:

• Accumulation (Mass Gains): Direct snowfall, wind-drifted snow, snow/ice avalanches off steep valley walls (crucial in deep Himalayan gorges!), and refreezing meltwater/rime.
• Ablation (Mass Losses): Surface and basal melting followed by runoff, direct ice-to-vapour sublimation in dry windy air, wind deflation, and iceberg calving into lakes or seas.

Comparing total gains against total losses over a hydrological year defines glacier mass balance (positive when net mass grows, negative when net mass shrinks). On most glaciers, an upper accumulation zone (net annual gain) meets a lower ablation zone (net annual loss) along the equilibrium line, whose elevation is the Equilibrium-Line Altitude (ELA). Do not automatically equate the ELA with the visible snowline on any random day: late-summer snowlines often approximate the annual ELA on clean glaciers, but fresh summer storms, shaded snow patches, superimposed refrozen ice, or thick rock debris frequently separate the observed snowline from the true mass-balance ELA. Moreover, mass balance alters ice thickness and flux first, whereas glacier length responds only after a dynamic response-time lag (years on short steep tongues to decades/centuries on long thick trunks)—so a single hot summer or brief 1-year advance never proves a regional climate trend by itself!

2.1 How Solid Ice Moves—and Why Retreat Is Never Uphill Flow

Glaciers move down the slope of their upper ice surface (which allows thick ice to push locally uphill over minor bedrock bumps on the buried valley floor so long as the top ice surface slopes downward!). Three physical mechanisms drive ice motion in varying proportions:

1. Internal Plastic Deformation (Creep): Below a brittle upper crust (~30–50 m deep, where stretching opens tension cracks called crevasses over bed steps, bends, or spreading lobes), high overburden pressure makes solid ice crystals slip along internal atomic planes and recrystallise without melting.
2. Basal Sliding (Warm-Based / Temperate Glaciers): Where basal ice is at its pressure-melting point, a thin film and cavities of pressurised liquid meltwater reduce bed friction so the ice slides across bedrock—though channelised subglacial tunnels can drain water pressure and slow sliding seasonally! (Conversely, cold-based polar glaciers remain frozen solid to their beds at sub-zero temperatures, moving almost solely by slow internal creep.)
3. Subglacial Bed Deformation: Where wet, unconsolidated till or mud underlies the ice, high pore-water pressure lets the soft sediment layer itself shear like a deformable carpet beneath the glacier.

Crucial Prelims Safeguard — Ice Motion vs Terminus Position: A glacier's lower snout (terminus) advances when ice delivery exceeds frontal ablation, stands stationary when delivery equals ablation, and retreats when frontal ablation outpaces ice delivery. Even during rapid glacier retreat, every ice crystal inside the glacier continues flowing downhill toward the snout! A simple conveyor-belt calculation shows why: suppose a valley glacier's internal creep and basal sliding carry ice downhill at +20 metres per year toward the snout. If summer ablation melts 20 metres per year at the front, the terminus stands stationary (+20 − 20 = 0 m/yr, dumping a tall terminal moraine ridge in one spot). If a warming climate raises frontal melting to 35 metres per year while the ice continues moving downhill at +20 metres per year, the snout position retreats up-valley by −15 metres per year (+20 − 35 = −15 m/yr)—even though every boulder frozen inside the ice moved 20 metres downhill that year!

3. Glacial Erosion and Alpine Landforms: Cirques, Arêtes, Horns & Roches Moutonnées

Moving glaciers erode bedrock through two primary processes whose effectiveness depends on basal sliding speed, basal debris supply, subglacial water-pressure swings, and rock jointing—meaning a thinner, fast-sliding temperate glacier erodes far faster than a thick polar glacier frozen cold to its bed:

• Glacial Abrasion (Sandpapering): Rock clasts frozen into basal ice grind against bedrock under immense weight, polishing rock smooth, pulverising silt-sized glacial rock flour (which turns meltwater streams milky turquoise), and scratching linear grooves and striations aligned with local basal flow.
• Plucking / Quarrying (Block Removal): Meltwater penetrates joints and fractures on the downstream low-pressure side of bedrock bumps, refreezes or fluctuates in pressure, and lets moving ice rip out entire angular rock blocks—quantitatively removing even more bedrock volume than abrasion in well-jointed granite or gneiss!

3.1 Highland Erosional Sculptures

In glaciated mountains, ice excavation works alongside frost shattering and rockfall on exposed cliffs above the ice—forming classic alpine features without forcing every peak through one mandatory sequence:

• Cirque (Corrie / Cwm), Bergschrund & Tarn: Near the top of a cirque glacier, moving ice pulls away from stagnant upper ice or the rock headwall to open a deep transverse head-crevasse called a bergschrund (or rock-wall randkluft), allowing summer meltwater and temperature swings to reach deep rock joints. Combined with rotational basal sliding, headwall plucking, and floor abrasion, this hollows out a deep armchair-shaped amphitheatre bounded downstream by a raised rock threshold lip. After deglaciation, water ponded behind that rock lip forms a circular mountain lake called a tarn (or corrie lake, e.g., Chandra Tal or Suraj Tal environments and high Garhwal/Sikkim cirque lakes).
• Arête & Pyramidal Peak (Horn): Where two adjacent cirques or glacial troughs erode headward from opposite sides of a divide, they narrow the intervening ridge into a serrated, knife-edged crest called an arête. Where three or more cirques bite inward around a central summit, steep headwalls intersect to leave a sharp pyramidal peak / horn (classic globally at the Matterhorn, and in the Himalaya–Karakoram at peaks like Shivling, Nilkanth, and Ama Dablam).
• Nunatak: An isolated rocky mountain peak protruding like an island above a surrounding ice sheet or ice field, often jagged from frost wedging while spared glacial scouring below.
• Roche Moutonnée ("Sheepback" Bedrock Knob): An asymmetric glacially moulded bedrock whaleback whose upstream (stoss) side is ground smooth and gently sloping by abrasion, whereas its downstream (lee) side is steep, rough, and jagged from joint-block plucking!

4. Glacial Valleys: U-Shaped Troughs, Truncated Spurs, Hanging Valleys & Fjords

Glaciers rarely carve brand-new valleys from scratch; instead, thick valley glaciers occupy pre-existing V-shaped river valleys from wall to wall. Because ice fills the entire cross-section rather than hugging a narrow thalweg, lateral and basal erosion shears off interlocking river valley bends—leaving triangular cliff facets called truncated spurs—and widens and deepens the valley into a steep-walled, broad-floored U-shaped glacial trough (modified later by post-glacial talus cones and braided river alluvium).

Down-valley, differential plucking across jointed vs massive rock steps carves giant rock staircases containing overdeepened basins that hold strings of paternoster ("rosary-bead") lakes. Meanwhile, because a thick trunk glacier erodes its floor far deeper than smaller, thinner tributary glaciers joining from side valleys, deglaciation leaves tributary valley floors perched high up on the main trough wall as hanging valleys—from which post-glacial streams plunge as spectacular waterfalls! Finally, where a coastal glacier scours a deep U-shaped trough far below present sea level (aided by ice thickness allowing erosion below ocean level before buoyancy lifts the snout) and post-glacial sea-level rise floods the trough, a deep, steep-walled marine inlet with a shallow mouth sill forms—a fjord (classic in Norway, Chile, Alaska, and New Zealand's Milford Sound; strictly distinct from rias, which are drowned V-shaped river valleys without glacial excavation!).

5. Unsorted Till vs Sorted Meltwater Deposits and the Moraine Family

Glaciers carry rock debris in three positions: supraglacial (fallen onto the ice surface from valley cliffs), englacial (buried inside the ice body), and subglacial (dragged along the bed). How that debris is eventually laid down creates a fundamental textural split across all glaciated landscapes:

• Glacial Till (Direct Ice Deposition — Unsorted & Unstratified): Solid ice has zero ability to winnow particles by weight—it drops microscopic clay flour, sand, angular pebbles, and 50-tonne boulders all jumbled together as unsorted, unstratified till (part of the broader glacial sediment umbrella called glacial drift).
• Glaciofluvial & Glaciolacustrine Deposits (Meltwater Deposition — Sorted & Stratified!): Once liquid meltwater picks up debris, it behaves like any river or lake—sorting cobbles, gravel, and cross-bedded sand across braided glaciofluvial outwash streams, and settling seasonal summer-silt / winter-clay couplets called varves on quiet glaciolacustrine lake floors. Never assume every deposit near a glacier is unsorted till!

5.1 Moraines: Landform Ridges Marking Transport Paths and Ice Margins

Keep sediment and landform distinct: till names the unsorted sediment, whereas a moraine names a geomorphic ridge, band, or sheet built along an ice margin or beneath wasting ice (often containing till alongside water-reworked lenses):

• Lateral Moraines: Steep-sided ridges of frost-shattered cliff debris carried along the left and right margins of a valley glacier and left banking the valley walls after ice melts.
• Medial Moraine: A dark central debris stripe running down the middle of a compound glacier formed where two tributary glaciers converge and unite their inner lateral moraines (often poorly preserved as a ridge once ice melts completely).
• End Moraines — Terminal vs Recessional: Ridges dumped along a stationary snout where forward ice conveyor-delivery balances frontal melting. The outermost ridge marking the farthest limit of a glacial advance is the terminal moraine; ridges built during temporary pauses or minor readvances inside that outer limit during overall retreat are recessional moraines.
• Ground Moraine: Gently rolling, hummocky blankets of subglacial lodgement and melt-out till spread across broad plains beneath an ice sheet or valley floor.

6. Drumlins, Eskers, Kames, Kettles, Glacial Lakes & Isostatic Rebound

Beyond moraine ridges, retreating ice sheets and valley glaciers leave diagnostic clues to ice flow direction, meltwater tunnels, lake dams, and crustal loading:

• Glacial Erratics: Boulders (from cobbles to house-sized blocks) transported by ice and dropped onto completely foreign bedrock tens or hundreds of kilometres from their source outcrop—allowing geologists to trace ancient ice-flow trajectories.
• Drumlins ("Basket-of-Eggs" Subglacial Hills): Smooth, elongated, inverted-spoon-shaped hills (~15–50 m high, 0.5–2 km long) moulded beneath flowing ice primarily out of glacial till and sediment, typically occurring in swarms aligned parallel to ice movement. Crucial UPSC Prelims Contrast with Roche Moutonnée: A depositional/subglacial drumlin has its steeper, blunter nose facing UPSTREAM (stoss) and tapers gently DOWNSTREAM (lee)—the exact opposite asymmetry of an erosional bedrock roche moutonnée (gentle smooth stoss upstream, steep plucked lee downstream)!
• Eskers (Subglacial Meltwater Tunnel Ridges): Long, sinuous, embankment-like ridges of water-sorted sand and gravel (metres to tens of metres high, winding for kilometres—even uphill across minor valley undulations!) deposited inside pressurised meltwater tunnels choked with sediment at the base of stagnant ice; when the surrounding ice walls melt away, the tunnel bed remains standing as a raised ridge.
• Kames, Kettle Holes & Outwash Plains (Sandur): Kames are irregular mounds or flat-topped terraces of stratified sand/gravel washed into crevasses, moulins, or hollows against stagnant ice margins. Where huge detached blocks of "dead ice" get buried inside outwash sand and later melt out, the overlying sediment collapses into closed depressions called kettle holes (filling with water as kettle lakes across a pitted outwash plain / sandur).

6.1 Diverse Glacial Lake Origins & Post-Glacial Isostatic Adjustment

Glacial lakes form through at least four distinct mechanisms: (1) bedrock-scoured basins (cirque tarns, valley paternoster lakes, Great Lakes), (2) dead-ice thaw hollows (kettle lakes), (3) side-valley lakes blocked by live glacier ice, and (4) moraine-dammed proglacial lakes ponded between a retreating glacier snout and its loose, steep end-moraine ridge. Because unconsolidated end moraines often contain buried ice cores and weak sand/boulder matrices, rock/ice avalanches, extreme rain, or piping can breach the dam and unleash a Glacial Lake Outburst Flood (GLOF)—though lake presence alone never proves imminent outburst without assessing dam geometry, freeboard, and slope stability!

At continental scale, 2–3-km-thick Pleistocene ice sheets depressed Earth's elastic-viscous lithosphere hundreds of metres downward into the asthenosphere while pushing viscous mantle rock outward into a peripheral forebulge. Since ice sheets melted (~20–8 ka), mantle rock has been slowly flowing back underneath Scandinavia and Hudson Bay—lifting formerly glaciated coasts upward at ~8–11 mm/year (creating raised beaches) while peripheral forebulges slowly subside, a continuing crust-mantle process called glacial isostatic adjustment (postglacial rebound).

7. Periglacial Environments: Permafrost, Active Layer, Taliks & Ground Freezing

First, clear up the word itself: although Polish geographer Walery Łoziński coined periglacial (1909) around Pleistocene ice-sheet margins, in modern geomorphology periglacial does NOT mean "next to a glacier"! Instead, it defines cold, non-glacial environments dominated by intense freeze–thaw cycles, seasonal ground freezing, and perennial ground ice—covering vast glacier-free expanses of interior Siberia, northern Canada/Alaska, and arid high-altitude plateaus of Ladakh and Tibet thousands of kilometres from any ice sheet.

7.1 Permafrost, the Active Layer, and Taliks

• Permafrost (Strict Thermal Definition): Any soil, sediment, peat, or solid bedrock whose temperature remains at or below 0 °C continuously for at least two consecutive years. Notice that permafrost is defined solely by temperature and duration, not moisture: dry, unweathered cold granite ("dry permafrost") qualifies just as much as ice-cemented silt, and permafrost is completely distinct from moving snow-derived glacier ice! Regional coverage grades from continuous permafrost (>90% area underlain), through discontinuous (50–90%), to sporadic (<50%) and high-mountain alpine permafrost.
• Active Layer vs Seasonally Frozen Ground: Directly atop permafrost sits the active layer (~0.3 to 3 m thick)—the surface zone that thaws every summer and refreezes every winter, hosting all root growth, soil hydrology, and freeze–thaw churning. (Where deep permafrost is absent altogether and ground merely freezes in winter and thaws completely in spring, call it seasonally frozen ground, not an active layer.)
• Talik: A localized pocket or layer of year-round unfrozen ground inside a permafrost region—commonly maintained beneath deep lakes and large rivers whose bottom water never freezes solid (open/through taliks), or trapped temporally between deepening winter frost and deeper permafrost.

7.2 Ice Segregation, Frost Heave, Patterned Ground & Solifluction

When winter cold penetrates downward into moist silty soil, water does far more than expand by 9% in place! Capillary suction draws unfrozen film water upward toward the freezing plane to feed growing horizontal layers of pure ice—ice segregation—pushing overlying soil and stones upward as frost heave. How does frost heave ratchet a heavy stone upward to the surface against gravity? Through a two-step winter-and-spring ratchet: (1) Winter Frost-Push & Frost-Pull: Solid rock conducts winter cold roughly two to three times faster than damp silty soil, so the 0 °C freezing front reaches the bottom of a buried cobble before the surrounding silt freezes; capillary water migrates to that cold base to form an ice lens underneath the stone while freezing silt grips the stone's upper sides, heaving the cobble upward by 1–2 centimetres. (2) Spring Thaw Infilling: When spring warmth thaws the soil from the top down, soft wet silt slumps into the tiny cavity underneath the lifted cobble before the deeper ice lens fully melts—blocking the stone from settling back to its original depth! Repeated over hundreds of winters, this one-way ratchet jacks stones to the surface while freeze–thaw churning (cryoturbation) sorts them into geometric circles, nets, polygons, and downslope stone stripes collectively called patterned ground.

When summer thaws the upper active layer, meltwater cannot drain downward through the impermeable frozen permafrost floor below! Saturated, porridge-like active-layer mud therefore creeps slowly (centimetres per year) down remarkably gentle slopes (even 2°–5°!), building overlapping tongue-shaped terraces called solifluction lobes (specifically termed gelifluction where permafrost forms the frozen sliding floor).

8. Nivation, Blockfields, Rock Glaciers, Ice Wedges, Pingos & Thermokarst

Six distinctive cold-region landforms complete the periglacial landscape—each with a specific physical origin that Prelims examiners test closely:

• Nivation Hollows: Shallow hillside benches beneath late-lying seasonal snowbanks where repeated freeze–thaw shattering round the snow margin, slopewash, and solifluction jointly excavate a miniature amphitheatre (without true glacier flow, though continued snow accumulation can turn a nivation hollow into a full cirque).
• Blockfields (Felsenmeer — "Sea of Rocks"): Broad, angular boulder mantles blanketing flat high plateaus and mountain summits, produced by prolonged frost wedging along bedrock joints combined with inherited pre-glacial deep weathering.
• Rock Glaciers: Lobate or tongue-shaped masses of coarse angular talus boulders (hundreds of metres to kilometres long, corrugated with wrinkly surface ridges like lava flows) cemented internally by interstitial pore ice or a buried glacier-ice core, creeping slowly downslope at centimetres to decimetres per year. Do not confuse an active rock glacier with an ordinary valley glacier merely dusted with thin surface stones!
• Thermal-Contraction Ice Wedges: In bitter Arctic winters (below −15 to −20 °C), frozen ground contracts and cracks into a honeycomb polygon network (just like drying mud). Spring snowmelt trickles into the open vertical crack and freezes immediately into a thin vein of ice; repeated winter cracking and spring refilling over centuries widens the vein into a V-shaped ice wedge (1–3 m wide at top, 5–10 m deep), outlining classic ice-wedge polygons.
• Pingos (Ice-Cored Permafrost Hills): Conical, soil-covered mounds (5–50+ m high, up to 500 m wide, often split at the summit by radial dilation cracks) pushed upward by a growing lens-like core of massive ground ice! Two classic pathways build pingos: (1) Hydrostatic (Closed-System) Pingos on flat Arctic coastal plains (like Canada's Mackenzie Delta), when a shallow thaw lake drains so permafrost encroaches inward from all sides around the unfrozen lake-bed talik, squeezing pore water upward to freeze into an ice core; and (2) Hydraulic (Open-System) Pingos on valley footslopes (common in East Greenland, interior Alaska, and high Central Asia/Ladakh), where sub-permafrost artesian groundwater flows downslope under hydraulic head and freezes near the surface.
• Thermokarst (Thaw Subsidence Terrain): When climate warming, wildfire, or tundra disturbance melts ice-rich permafrost (especially massive ice wedges), the ground loses solid ice volume and collapses unevenly into waterlogged pits, retrogressive thaw slumps, beaded streams, and shallow thaw depressions/lakes (alas basins in Siberia)—physically distinct from chemical limestone karst!

9. Climate Thresholds and the Himalayan–Karakoram Cryosphere

Often called Earth's "Third Pole", the Hindu Kush–Karakoram–Himalayan (HKKH) mountain arc stores the largest volume of snow, glacier ice, and alpine permafrost outside Antarctica and the Arctic—obeying the exact physical balances and thresholds developed above:

• Major Indian Cryospheric & Quaternary Landmarks: The Karakoram hosts giant valley glaciers tens of kilometres long—led by the Siachen Glacier (~76 km) in the Nubra valley (Ladakh), alongside Biafo, Baltoro, and Rimo—while the Great Himalaya hosts Gangotri (~30 km) and Satopanth in Uttarakhand, Bara Shigri (~28 km) and Chhota Shigri in Lahaul–Spiti (Himachal Pradesh), Milam and Pindari in Kumaon, and Zemu (~26 km) on Kanchenjunga's flank in Sikkim. (In the intermontane Kashmir Valley, Pleistocene glaciolacustrine clays, silts, sands, and morainic gravels laid down in ancient ice-age Lake Karewa remain preserved as flat-topped terrace mounds—the famous Karewas supporting Pampore's GI-tagged Zafran saffron orchards!)
• Winter-Westerlies vs Summer-Monsoon Regimes: Karakoram and western Himalayan/Lahaul glaciers receive most snowfall in winter from Western Disturbances, whereas central and eastern Himalayan glaciers (Nepal, Sikkim, Arunachal) are summer-accumulation glaciers fed simultaneously while melting during the warm Indian Summer Monsoon—making eastern/central ELA heights exquisitely sensitive to slight summer warming (which flips high-altitude monsoon snow into rain!). (Parts of the central Karakoram displayed near-balanced or slightly positive mass budgets around the turn of the 21st century—the Karakoram Anomaly—linked to high elevations, winter westerly snow, and summer cloud cooling, though recent satellite gravimetry shows growing mass losses spreading across most of High Mountain Asia.)
• The Supraglacial Debris-Cover Threshold: Steep Himalayan rockwalls shower lower glacier tongues with heavy landslide and rockfall rubble. A very thin dark dust/soot coating (<1–2 cm) lowers ice albedo, absorbs solar radiation, and accelerates melting; once supraglacial rock debris thickens beyond ~3–5 cm, however, the rocky blanket thermally insulates underlying ice—slowing surface melt even while steep exposed ice cliffs and supraglacial ponds become local melt hotspots!
• Moraine-Dammed Lakes & Trans-Himalayan Permafrost: As debris-covered Himalayan tongues thin and retreat behind tall Little Ice Age terminal moraines, meltwater ponds expand rapidly into hundreds of moraine-dammed proglacial lakes (monitored by ISRO's Space Applications Centre and NDMA—illustrated vividly by the October 2023 South Lhonak Lake outburst flood down Sikkim's Teesta valley after a lateral-moraine slope failure, and lakes such as Gepang Gath in Himachal). Meanwhile, across rain-shadow Ladakh, Changthang, Zanskar, and Spiti above ~4,500 m, vast periglacial belts host alpine permafrost, active rock glaciers, frost-sorted patterned ground, solifluction slopes, and seasonal frost-heave hazards along high mountain highways. Always remember: published counts of Himalayan glaciers (~9,575 in GSI's Indian Himalayan inventory), retreat rates, and lake totals depend strictly on minimum-area cutoffs, debris-boundary rules, satellite resolution, and observation dates—so always cite them as dated measurements rather than timeless constants!

10. Synthesis: Reading Moving Ice and Frozen Ground Together

Cold landscapes become effortless to interpret once you separate moving glacier ice from frozen ground and connect every landform back to its physical budget:

• Glaciers require perennial snow accumulation, compaction through firn into airtight crystalline ice, and sufficient thickness to creep and slide downhill under gravity. Mass balance sets long-term ice volume across the Equilibrium-Line Altitude, geometry introduces response lags, and terminus retreat always reflects frontal ablation exceeding downhill ice delivery—never backward flow.
• Glacial landforms split cleanly into bedrock erosion (cirques, arêtes, horns, U-shaped troughs, hanging valleys, fjords, smooth-stoss/plucked-lee roches moutonnées), direct unsorted ice till (lateral, medial, terminal, recessional, and ground moraines; blunt-stoss/tapered-lee drumlins), and sorted meltwater outwash (winding eskers, ice-contact kames, dead-ice kettle lakes, varved lake beds).
• Periglacial terrains operate wherever deep frost and permafrost (≤0 °C for ≥2 years) govern the ground—even far from any glacier—heaving and sorting stones via ice segregation, creeping summer-thawed active layers over impermeable frost as solifluction lobes, cracking winter ground into ice-wedge polygons, jacking up ice-cored pingos, and subsiding into thermokarst hollows when ground ice thaws.

11. Practice Questions & Frequently Asked Questions

Test your conceptual clarity across glaciology, glacial vs glaciofluvial landforms, permafrost mechanics, and the Himalayan cryosphere with eight UPSC Prelims-style questions and five FAQs.

Frequently Asked Questions