Cycle of Erosion, Rejuvenation and Polycyclic Relief: Terminology for UPSC Geography Optional

The cycle-of-erosion family is the vocabulary UPSC uses to ask how a landscape ages and what happens when uplift or a fall of sea level resets the clock. It covers William Morris Davis’s stages and peneplain, Walther Penck’s German terms, rejuvenation and the landforms that record more than one cycle. It is the most frequently examined cluster in Geomorphology, and every term predicts a landscape you can recognise.

Read each entry definition first, then the mechanism, examples and sketch line. UPSC has asked the peneplain (2004, 2023), the epigene cycle (2012), the treppen concept (1993), rejuvenation (1989, 1992), incised meanders (2014), polycyclic landforms (1991, 1997) and the second cycle of erosion (2009); those entries are written to answer length.

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Davis’s Cycle and Its End-Forms

Geographical cycle (cycle of erosion)

The geographical cycle is William Morris Davis’s model (1899) in which a landmass, raised quickly and then left tectonically still, is worn down by weathering and running water through the stages of youth, maturity and old age to a low, rolling plain near base level, the peneplain. It dominated geomorphology until about 1950.

• Assumptions: rapid, brief uplift of a block of uniform rock; negligible erosion until uplift stops; a long stillstand; a fixed base level set by the sea; a humid-temperate climate with running water as the main agent. Davis framed landscape as a function of structure, process and stage.
• Mechanism (the Davis graph): two curves are plotted against time, an upper one for divide summits and a lower one for valley floors. In youth the lower curve drops fast while the upper stays level, so relative relief rises to a maximum; in maturity both fall; in old age both converge slowly on base level. Old age lasts longer than youth and maturity together.
• What it predicts: V-shaped, then broad, then flat valleys; drainage density rising and then falling; slopes changing from convex to concave; a near-level end-form.
• Criticism: uplift is slow and long-continued, erosion runs alongside it and long stillstands are rare. Arthur Newell Strahler, John Tilton Hack and Richard John Chorley replaced the cycle with dynamic equilibrium, in which form reflects present process rather than age.
• Davis versus Penck in one line: for Davis a landform records how long erosion has acted; for Walther Penck it records how fast uplift runs relative to erosion.
• Sketch: the Davis graph (altitude against time), the two curves diverging in youth and converging just above base level in old age.

Stages of youth, maturity and old age

Youth, maturity and old age are the three successive stages of the geographical cycle, each subdivided into early, middle and late. A stage is identified from landform evidence, namely the balance between vertical and lateral erosion, the shape of valleys and interfluves and the relief remaining, not from years: a young landscape can be geologically old.

• Examples: youth in the transverse gorges of the Alaknanda and Bhagirathi, Garhwal Himalaya; old age on the rolling central Ranchi plateau, Jharkhand.
• Don’t confuse with: the stage of a single river reach. The upper course of a river can be youthful while its lower course is old, whereas Davis’s stages describe a whole landscape.
• Sketch: three cross-profiles labelled youth, maturity and old age, divides lowering and valleys widening.

Normal (epigene) cycle

The normal cycle of erosion is the standard fluvial version of the geographical cycle, worked out by William Morris Davis for humid-temperate lands where running water is the principal agent. “Epigene” means acting at the Earth’s surface. Davis called it normal because rivers shape more of the land than any other agent, so it became the yardstick for the arid, glacial, karst and marine cycles.

• Conditions assumed: uniform rock; fast, brief uplift, then a long stillstand; sea level as fixed base; perennial streams; no climatic change.
• Drainage evolution: consequents form on the initial slope, subsequents etch out weak belts and captures integrate the network in youth; maturity has a graded network; in old age rivers are fewer, sluggish and meandering.
• Relief and energy: absolute relief falls throughout, while relative relief rises in youth, peaks in early maturity and declines in old age. Rivers have surplus energy in youth (downcutting), balance energy and load in maturity (the graded river), and become overloaded and aggrade in old age.
• Slopes and end-product: valley sides decline from convex to rectilinear to concave by downwasting, unlike parallel retreat; the end-product is a peneplain with monadnocks, and old age is the longest stage.
• Contrast with other cycles: in the arid cycle base level is local; in the karst cycle underground drainage takes over. Lester Charles King later gave the name “epigene cycle” to his own scarp-retreat cycle.
• Examples and sketch: Davis’s own model country was the Appalachians and southern New England; the peneplained Chotanagpur surfaces are the Indian illustration. Draw three block diagrams (youth, maturity, old age) with the drainage network growing and then simplifying.

Peneplain

A peneplain (Latin paene, “almost”, plus plain) is the gently undulating, low-relief surface near base level that William Morris Davis, who coined the word in 1889, placed at the end of the fluvial cycle of erosion. It is produced by long downwasting and slope decline, cuts across rock structures regardless of their hardness or dip, and is dotted with residual hills called monadnocks.

• Formation: in old age valley deepening ceases; lateral erosion, weathering and soil creep lower divides faster than valley floors; slopes decline and become concave; interfluves shrink to low swells. Davis called it a near end-product because base level can be approached but never reached.
• Key features: regional extent; low relief and altitude; convexo-concave divides; broad valleys with meandering rivers; a thick weathered mantle; truncated folded or dipping beds; monadnocks.
• Peneplain-type surfaces in other cycles (the 2023 demand): Walther Penck’s Endrumpf (a plain of concave waning slopes), Colin Hayter Crickmay’s panplain (coalesced floodplains), Lester Charles King’s pediplain (coalesced pediments with inselbergs), the etchplain of deep tropical weathering, the karst plain studded with residual hums, and the periglacial cryoplain. The associated landforms identify the cycle that produced the surface.
• Examples: the Schooley peneplain of the Appalachians (New Jersey and Pennsylvania), now uplifted as accordant ridge crests; in India, the central Ranchi plateau surface at about 600 m, whose uplifted continuation lies at about 900 m beneath the laterite-capped pats of the west.
• Criticism: no peneplain stands at base level today and the crust rarely stays still long enough; Davis replied that only surfaces uplifted after formation survive to be seen. Equal-height divides can also arise without any former plain (see accordant summit levels).
• Sketch: a rolling surface truncating tilted beds, with a monadnock, a meandering river and base level just below.

Monadnock and unaka

A monadnock is an isolated residual hill rising above a peneplain, left standing because it wasted more slowly than the surrounding land. An unaka is a residual mass or group of monadnocks too broad to be called a single hill. Both names are Appalachian: William Morris Davis named the monadnock after Mount Monadnock, New Hampshire, and the unaka is named after the Unaka Mountains on the Tennessee–North Carolina border.

• Formation: differential erosion in old age. German usage separates the Härtling, surviving because its rock is harder, from the Fernling, surviving because it lies far from the main rivers.
• Key features: a convexo-concave profile, often capped by quartzite or granite.
• Examples: Mount Monadnock (about 965 m) above the New England upland; in India, Parasnath hill (about 1,350 m) above the Hazaribagh plateau, and the granite dungris that stand over the peneplained central plateau of south-east Chotanagpur.
• Don’t confuse with: an inselberg, a steep-sided residual left by scarp retreat on a savanna or arid pediplain, not a gentle residual of downwasting.
• Sketch: a low rolling line with one rounded hill labelled monadnock and a cluster of broader rises labelled unaka.

Panplain and panplanation

Panplanation is Colin Hayter Crickmay’s mechanism (1933) of late-cycle planation by the lateral erosion of meandering rivers, and the panplain is its end-product: a flat plain formed when widening floodplains coalesce after the interfluves between them have been consumed by undercutting.

• Mechanism: divides are cut away from the side by rivers swinging against them, not lowered from the top by slope decline as in the Davisian model; floodplain margins stay as steep bluffs because the river keeps undercutting them.
• Key features: a level rather than undulating surface; a thin alluvial veneer; steep-sided residual hills; surfaces at several levels can coexist, because lateral planation at a lower level need not destroy a higher one.
• Assessment: Crickmay overstated the power of lateral erosion and the model won little support, but it explains why many old-age plains are flatter than a Davisian peneplain should be.
• Don’t confuse with: the peneplain (downwasting, rolling surface) or the pediplain (scarp retreat and pediments).
• Sketch: plan view of three floodplains widening until the interfluves between them vanish into one confluence plain.

Penck’s Vocabulary

Primärrumpf and Endrumpf

Primärrumpf (German, “primary peneplain”) is Walther Penck’s term for the low, gently convex surface that exists while a region begins to rise so slowly that denudation keeps pace, so relief never grows. Endrumpf (“end peneplain”) is the low plain of concave slopes that remains when uplift has stopped and waning development has consumed the relief; it is Penck’s counterpart of the peneplain.

• What each predicts: a Primärrumpf shows broad, subdued convex forms, no deep valleys and truncated but undissected beds; an Endrumpf shows concave footslopes meeting in a plain with scattered residual hills, produced by the extension of gentle lower slope units from below (see slope replacement) rather than by Davisian decline from above.
• Key contrast: Davis’s cycle starts from a high, just-uplifted block, whereas Penck’s starts from a low Primärrumpf that rises gradually, so the beginning of Penck’s sequence is subdued, not rugged.
• Context: Penck (1888–1923) died young; his main work appeared posthumously in 1924, and poor translation long obscured these terms in English.
• Don’t confuse with: Rumpffläche, the general German word for any planation surface.
• Sketch: Penck’s graph with the uplift curve, the divide curve and the valley-floor curve starting low (Primärrumpf) and ending low (Endrumpf).

Aufsteigende, gleichförmige and absteigende Entwicklung

Aufsteigende, gleichförmige and absteigende Entwicklung (waxing, uniform and waning development) are Walther Penck’s replacements for Davis’s youth, maturity and old age. They describe not elapsed time but the ratio between the rate of uplift and the rate of erosion, and each ratio predicts a characteristic valley-side slope: convex, straight or concave.

• Aufsteigende Entwicklung (waxing development): uplift outpaces incision; rivers cut narrow V-shaped valleys; absolute and relative relief rise; valley sides are convex.
• Gleichförmige Entwicklung (uniform development): uplift and incision run at equal rates; relative relief stays constant; valley sides are straight and retreat parallel to themselves.
• Absteigende Entwicklung (waning development): uplift slows and stops; slope retreat outpaces incision; relief declines; valley sides become concave as the gentle lower unit extends upslope (the Haldenhang–Böschung process is covered under slope replacement).
• Exam use: read a valley-side profile and infer tectonic tempo. The convex, steep walls of the transverse Himalayan valleys point to continuing uplift; the concave, pediment-fringed slopes of the Peninsular shield point to long quiescence.
• Criticism: rock type and climate also shape slopes, so slope form alone is a weak guide to uplift rate.
• Sketch: three valley cross-profiles (convex, straight, concave), each labelled with its uplift-to-erosion ratio.

Piedmonttreppen (piedmont treppen, treppen concept)

Piedmonttreppen (German, “piedmont stairway”) is Walther Penck’s term, published in 1924, for a staircase of erosional benches (Piedmontflächen) ringing a dome that rises at an accelerating rate while expanding outward. Each bench is cut at the dome’s margin during slower relative uplift and is then raised and replaced outside by a lower one, so the highest, innermost bench is the oldest.

• Mechanism: doming spreads outward; streams draining the dome grade to local base levels at its margin and cut a bench there; as the uplifting area widens, that bench is lifted and a new, lower bench is cut beyond it. The whole flight therefore forms during one episode of widening uplift, not through a series of separate Davisian cycles.
• Key features: concentric benches descending outward; benches narrowing headward along valleys; steep risers or knick zones between steps; the uppermost level is a Primärrumpf-like summit flat.
• Examples: the Black Forest (Schwarzwald) of south-west Germany, Penck’s type area; the South Swedish Dome, where the sub-Cambrian surface and successively lower surfaces step down outward. The stepped levels of the Chotanagpur plateau (about 900, 600 and 300 m) are the nearest Indian analogue, though they are usually explained by discrete Tertiary uplifts rather than one widening dome.
• Significance: the first model to explain stepped surfaces without several cycles, an early case of equifinality; Lester Charles King later likened his headward-extending pediplains to a treppen.
• Criticism: accelerated doming was assumed rather than shown independently, and applications to the Scandinavian mountains were rejected because that range is not a set of domes.
• Sketch: a half-dome cross-section with three or four benches descending outward; label the crest bench “oldest” and the outer bench “youngest”.

Interruption and Rejuvenation

Interruptions of the cycle (accidents)

An interruption is any event that disturbs a cycle of erosion before it reaches the peneplain stage. A base-level change lengthens or shortens the cycle, since a fall throws it back to youth and a rise hastens old-age aggradation, while an accident, in William Morris Davis’s term, is a climatic change or volcanic outpouring that closes the running cycle and starts a different one.

• Base-level interruptions: tectonic or eustatic; a fall causes rejuvenation, a rise drowns lower valleys and promotes aggradation.
• Climatic accidents: the onset of aridity or glaciation replaces the fluvial cycle with an arid or glacial one; a minor shift to wetter conditions may only rejuvenate the rivers.
• Volcanic accidents: lava floods bury the drainage and relief, and a new consequent network begins on the cooled lava surface.
• Examples: the Deccan Traps, erupted around the Cretaceous–Palaeogene boundary, buried the older Peninsular drainage, and streams cutting through the lava became superimposed on the rocks beneath; Pleistocene ice sheets closed fluvial cycles in northern Europe and North America.
• Sketch: the Davis graph with an abrupt step down in base level and the valley-floor curve restarting steeply.

Rejuvenation

Rejuvenation is the renewal of a river’s erosive power, above all its capacity to cut down, caused by a fall of base level, uplift or tilting of the land, or a gain in discharge relative to load. It interrupts the cycle and throws the affected valley back towards youth, starting a new cycle that works headward from the point of change.

• Dynamic rejuvenation: uplift, tilting or lowering of the outlet steepens gradients, as when Tertiary uplifts linked to Himalayan orogeny raised the western Chotanagpur plateau.
• Eustatic rejuvenation: a global fall of sea level, above all glacio-eustatic. At the Last Glacial Maximum sea level stood about 120 m lower and rivers cut deep valleys across the exposed shelf (see eustasy).
• Static rejuvenation: base level is unchanged but the river gains energy because its load decreases, its discharge rises through a wetter climate or meltwater, or it captures another stream (see river capture).
• Resulting landforms (the 1992 demand): knickpoints and knickpoint falls, two-storeyed valleys, paired terraces, incised meanders, uplifted peneplains, gorges cut into old valley floors and tributaries left hanging above the deepened trunk valley.
• Indian examples: the Narmada plunges about 30 m at Dhuandhar Falls into the marble gorge of Bhedaghat, near Jabalpur; the Subarnarekha drops 98 m at Hundru Falls off the Ranchi plateau; the lower Chambal runs in incised meanders among ravines attributed to uplift of the Himalayan foreland bulge; Western Ghats rivers leap the escarpment at Jog Falls (253 m, Sharavathi) and Shivanasamudra (Kaveri).
• Sketch: a long profile showing the old graded curve, a new steeper lower curve and the knickpoint where they meet, with a cross-section inset showing a valley within a valley.

Knickpoint and head of rejuvenation

A knickpoint (nickpoint) is a sharp break of gradient in a river’s long profile where a newer, steeper lower segment graded to a lowered base level meets the older, gentler upper segment. Because the steepened reach erodes fastest, the knickpoint migrates upstream, and its position at any moment is the head of rejuvenation, beyond which the valley still belongs to the older cycle.

• Formation: base-level fall or uplift produces cyclic knickpoints; a hard rock band or a fault produces non-cyclic ones, which must be ruled out first.
• Key features: waterfalls or rapids (knickpoint falls); a narrow gorge below and a wide, graded floor above; several knickpoints in one river record several episodes of rejuvenation.
• Examples: Niagara Falls has receded about 11 km since the ice withdrew some 12,500 years ago; on the Ranchi plateau margin, Hundru (Subarnarekha), Dassam (Kanchi) and Jonha (Raru) falls mark heads of Tertiary rejuvenation.
• Significance: distance travelled upstream, divided by a retreat rate, helps date an uplift; knickpoints also support the correlation of erosion surfaces.
• Don’t confuse with: the classification of waterfalls by structure (caprock, fault, hanging-valley falls), which belongs to fluvial landforms.
• Sketch: a concave long profile with a step, labelled knickpoint, and an arrow pointing upstream.

Incised meanders (entrenched and ingrown meanders)

Incised meanders are meander loops cut deep into bedrock when a river that had developed a meandering course on a gentle surface is rejuvenated and cuts downward while keeping its loops. John Lyon Rich (1914) separated two kinds: entrenched meanders, with symmetrical steep walls, and ingrown meanders, with an undercut outer bank and a long, gentle slip-off slope on the inner bank.

• Formation: the loop pattern is inherited from the older cycle; rejuvenation then drives incision. The ratio of vertical incision to lateral migration decides the type: rapid incision, from a fast pulse of uplift or very resistant rock, gives entrenched meanders; slower incision with continuing sideways shift gives ingrown meanders, whose loops enlarge as they deepen.
• Key features: entrenched meanders have a gorge-like, symmetrical section and loops effectively frozen in shape; ingrown meanders have cliffs on the concave bank and rock slip-off slopes on the convex bank. Where a neck is breached, the abandoned loop leaves a meander core, a hill ringed by a dry rock valley.
• Examples: the Goosenecks of the San Juan River, Utah, entrenched about 300 m into horizontal strata; the Moselle between Trier and Koblenz, Germany, the classic ingrown case; in India, the lower Chambal above its Yamuna confluence near Etawah, and the Damodar near Rajrappa, Jharkhand.
• Significance: symmetry records tempo, entrenched meaning a rapid pulse and ingrown a slow, prolonged uplift. Incised meanders also prove that the meanders existed before the uplift that deepened them.
• Don’t confuse with: free meanders that migrate across alluvium and cut off to form oxbow lakes; an incised meander is locked in rock.
• Sketch: two cross-sections side by side: symmetrical and steep (entrenched); cliffed outer bank with gentle slip-off slope (ingrown).

River terraces (paired and unpaired)

A river terrace is a flat bench on a valley side, bounded by a steep riser, that represents a former valley floor or floodplain abandoned when the river cut down to a lower level. Paired terraces stand at matching heights on both sides of the valley; unpaired terraces occur at different heights on alternate sides.

• Formation: paired terraces follow a rapid episode of incision through the whole old floor, typically rejuvenation; unpaired terraces form during slow downcutting while the river swings from side to side, trimming each bank at a different time.
• Types: strath (rock-cut) and fill (cut in valley alluvium) terraces, the rock benches being treated under straths and berms; by cause, tectonic, eustatic and climatic.
• Examples: the terrace flight of the Thames (Boyn Hill, Lynch Hill, Taplow), linked to Pleistocene sea-level and climatic changes; in India, the valley-fill terraces of the Alaknanda around Srinagar (Garhwal) and the two or three terrace levels, locally called bagar, of Kumaun’s Lesser Himalayan rivers.
• Current view: luminescence dating of Himalayan terraces ties many aggradation–incision swings to monsoon strength and sediment supply, not uplift alone (Quaternary dating).
• Sketch: a valley cross-section with two paired terraces labelled T1 and T2 on both banks and a separate unpaired set.

Two-storeyed valley and valley-in-valley topography

A two-storeyed (multi-storeyed) valley, or valley-in-valley, is a valley whose cross-profile shows a narrow, steep-sided young valley cut into the floor of an older, broad, flat-floored valley, the shoulders between them being remnants of the old floor. Each storey records a cycle, so three storeys mean two rejuvenations.

• Formation: a mature or old river with a wide floor is rejuvenated and incises a gorge into that floor; a second rejuvenation adds a third storey.
• Key features: paired shoulders at the break of slope; convex lower sides beneath concave upper ones; tributaries entering by falls from the old floor.
• Examples: the Damodar at Rajrappa (Ramgarh district, Jharkhand), where the Bhairavi (Bhera) tributary joins by a fall from the older floor; the Narmada below Dhuandhar Falls at Bhedaghat; Himalayan valleys of Uttarakhand with three storeys matching three phases of Tertiary uplift.
• Don’t confuse with: a glacial trough with a post-glacial river notch in its floor, which is valley-in-valley by a change of agent, not a change of base level.
• Sketch: a cross-profile with a broad upper valley, two shoulders and a narrow inner gorge.

Polycyclic Relief

Uplifted peneplain

An uplifted peneplain is a peneplain raised well above the base level to which it was cut and then dissected by rejuvenated rivers, so that it survives as accordant summits, flat-topped interfluves or high plateau remnants above a younger valley system.

• Recognition: accordant summits; structures truncated at summit level; a weathered or laterite cap; knickpoints where rivers leave the plateau; topographic discordance in the valleys.
• Examples: the Appalachian levels, from the oldest and highest Schooley surface down to the Harrisburg and Somerville surfaces; in India, the Patland of the western Ranchi plateau, where the old gneiss surface, once continuous with the central Ranchi surface at about 600 m, now lies about 300 m higher, near 900 m, beneath roughly 150 m of lateritised basalt.
• Current view: apparent uplifted peneplains may be warped, diachronous or partly structural, so they need independent dating (see dating of erosion surfaces).
• Sketch: a block diagram with flat, level ridge tops cut by deep valleys, and a dashed line joining the tops as the restored surface.

Topographic discordance

Topographic discordance is the juxtaposition, in one valley or slope profile, of older, gentler landforms above and younger, steeper landforms below, so that the landscape does not show a single consistent stage from divide to thalweg. It is the diagnostic signature of rejuvenation.

• Key features: a mature or old upper valley above a youthful gorge; a sharp break of slope (valley shoulder) at their junction; convex lower slopes beneath concave upper slopes; tributaries graded to the upper level rather than the lower.
• Where it appears: in cross-profiles, in long profiles (graded reaches above a knickpoint) and in whole landscapes (rolling uplands above gorges).
• Examples: the Narmada at Bhedaghat near Jabalpur, where a broad valley gives way to the marble gorge; the Damodar at Rajrappa.
• Don’t confuse with: topographic unconformity, the break between two regional erosion surfaces of different ages, or a geological unconformity between rock sequences.
• Sketch: a valley cross-section labelled “older, gentle forms” above and “younger, steep forms” below.

Polycyclic relief

Polycyclic (multicyclic) relief is a landscape that carries the imprint of two or more cycles of erosion, complete or partial, because repeated uplift, base-level change or climatic accidents interrupted each cycle before it finished. Remnants of older surfaces stand above younger valleys, so the landscape is a mosaic of forms of different ages rather than a single stage.

• Mechanism: each interruption starts a new cycle that works headward; old forms survive on divides until consumed, leaving a written-over record (see palimpsest topography).
• Evidence in the field: stepped surfaces and accordant summits; uplifted peneplains; knickpoints and knickpoint falls; two-storeyed valleys and paired terraces; incised meanders; hanging tributaries; topographic discordance; superimposed drainage.
• Regional study, Chotanagpur plateau (the 1997 demand): the Ranchi plateau carries an uplifted pre-Tertiary peneplain beneath the western pats, a true erosion surface on the central plateau and lower levels to the east and south (full sequence under erosion surfaces of peninsular India). Tertiary uplifts rejuvenated its rivers, which now fall off the plateau edge at Hundru, Dassam and Jonha, and the Damodar shows a two-storeyed valley at Rajrappa.
• Other examples: the Appalachians (Schooley, Harrisburg and Somerville levels); the Kumaun Himalaya, whose Lesser Himalayan rivers carry two or three terrace levels.
• Current view: John Tilton Hack argued that uniform rock and stream spacing can produce equal summit heights in dynamic equilibrium, without separate cycles, so a polycyclic reading must rest on deposits and dates, not on heights alone. The landscape-type classification is in fundamental concepts.
• Sketch: a block diagram with two surface levels separated by a scarp, a knickpoint fall and a valley within a valley.

Second cycle of erosion

The second cycle of erosion is the new cycle that begins when a landscape that had reached maturity or old age in a first cycle is uplifted or its base level falls, so that rejuvenated rivers start a fresh sequence of youth, maturity and old age inside the remains of the first. Its topography combines inherited first-cycle forms above with young second-cycle forms below.

• Inherited features: uplifted peneplain remnants and accordant summits; monadnocks of the first cycle standing above them; meander loops of the old floodplains, now incised; superimposed rivers carried down from a vanished cover.
• New features: knickpoints receding headward with falls and rapids at plateau edges; two-storeyed valleys and paired terraces; gorges; hanging tributaries; renewed river capture; and, in folded belts, resequent streams in the synclines after the first cycle has inverted the relief.
• Stage of the second cycle: it is itself usually incomplete, so its surface falls short of the first as a partial peneplain (see partial peneplains); a third cycle may then begin before the second is finished, and each such interruption adds another storey to the valleys.
• Examples: in the Appalachians the Harrisburg surface was cut after the Schooley surface was uplifted; on the Ranchi plateau the Tertiary cycle is entrenched in the pre-Tertiary peneplain; the Narmada below Dhuandhar Falls.
• Sketch: the Davis graph with the valley-floor curve steepening abruptly after a second uplift, beside a cross-section of a gorge cut into a broad old valley.

PYQs Built on These Terms

• Define Peneplains. Describe the landscape features associated with peneplains under different geomorphic cycles. (2023)
• Define the term ‘meander’ and describe the basic characteristics of entrenched meander and ingrown meander. (2014)
• Answer the following: Characteristics of the standard epigene cycle of erosion. (2012)
• Highlight the geomorphic features essentially found in topographies under the Second Cycle of erosion. (2009)
• Critically examine the concept of geomorphic cycle and discuss the views of W.M. Davis and W. Penck. (2008)
• Write short note: Peneplain (2004)
• Discuss the concept of polycyclic landforms and present an analytical study of the polycyclic landforms of a selected region. (1997)
• Write short note: Treppen concept. (1993)
• Explain the factors causing rejuvenation in landscape and describe the resultant landforms. (1992)

Frequently Asked Questions

What is the difference between a peneplain and a pediplain?

A peneplain is lowered from the top by downwasting and slope decline under humid conditions, leaving a rolling surface with gentle monadnocks. A pediplain grows from the side by parallel scarp retreat in semi-arid and savanna lands, leaving coalesced pediments with steep inselbergs. The first is William Morris Davis’s end-form, the second Lester Charles King’s.

What landforms show that a river has been rejuvenated?

Look for a break in the long profile with a waterfall or rapids, a narrow gorge cut into a broad old valley floor, paired terraces on both banks, meander loops sunk into bedrock and tributaries hanging above the main valley. The Narmada at Dhuandhar Falls and the Subarnarekha at Hundru Falls show several of these together.

How do entrenched meanders differ from ingrown meanders?

Entrenched meanders have symmetrical, steep walls because the river cut down so fast that it had no time to shift sideways. Ingrown meanders are asymmetrical, with a cliff on the outer bank and a long rock slope on the inner bank, because slower incision let the loops keep migrating. Both are incised meanders produced by rejuvenation.

How is Penck’s model different from Davis’s cycle of erosion?

Davis made landform a record of elapsed time, with uplift finished before erosion began. Walther Penck made landform a record of the ratio between uplift and erosion running together, replacing youth, maturity and old age with waxing, uniform and waning development, which predict convex, straight and concave slopes respectively.

What is an example of polycyclic relief in India?

The Chotanagpur plateau is the standard Indian example. Its western pats preserve an uplifted old peneplain, the central Ranchi plateau a younger surface, its rivers drop off the plateau edges at Hundru and Dassam falls, and the Damodar at Rajrappa has cut a young valley into an older one.

Why does a knickpoint move upstream?

The reach just below a knickpoint is steeper than the graded reach above, so flow there is faster and erodes harder. The step is worn back towards the headwaters, carrying the new base level up the valley; until it arrives, the valley above belongs to the older cycle.