Davis and Penk proposed different models of the cycle of erosion. Davis' model involved three stages - youth, maturity, and old age - where a landscape evolves from high relief to a flat plain over time. Penk emphasized the relationship between uplift and erosion, with landforms resulting from their competition. Later theorists like King and Gilbert built on these ideas but acknowledged no single model explains all landscapes given different environments. While influential, both Davis and Penk's concepts have limitations and underwent criticism regarding assumptions about rates of uplift and erosion.

1. CYCLE OF EROSION
:
PROPOUNDED BY DAVIS AND PENK
Presented by,
RAJITH K
1st Msc Geology
University of kerala

2. INTRODUCTION
Geomorphology: The study of landforms which is a composite result of
different exogenetic activities operated on land surface
Cycle of erosion: The balance between endogenetic and exogenetic
activities in a cyclic process
Exogenetic forces: (Denudational forces) Forces operating on lithospheric
surface and trying to eliminate the differences made by exogenetic forces

3. The above half of the circle shows exogenetic process, bringing the
elevated land to the sea level.

4. Categories of denudational forces
1. Weathering: Process which makes bedrock either weak,
fragmented or decomposed just near the earth surface( In-
Situ) or to a depth of few metres. Types are Physical and
Chemical weathering.
2. Erosion: Process which various erosive agents like running water,
wind, glacier, sea waves and underground water obtain and remove
rock debris from the earth crust and transport them for a long
distance.

5. CYCLES OF EROSION
At first William Moris Davis advanced the idea of “ Geomorphic cycle
of erosion”
He described and explained the distinctive characteristics possessed
by the landforms.
All the landscapes have definite life history after emergence.
In this way through different stages the elevated land become
featureless and flat plain known as Peneplain.

7. According to Davis,
“The geographic cycle is the period of time during which
an uplifted landmass undergoes its transformation by the process of
land sculpture ending in low featureless plain.”
Philip G. Worcester, accepted the geographic cycle but called it as the
“Cycle of erosion”. According to him,
“The cycle of erosion is the time required for streams to
reduce newly formed landmass to base level”

8. Dvais describe the landscape as the function of structure, process
and stage
• Structure: Means the nature of rock weather it is hard, soft,
previous
• Process: Determines the type of erosion
• Stage: Denotes weather the landmass undergoing its
transformation in young stage or in old stage

9. Davis assumptions,
• Each landscape has definite life history
• As soon as landmass emerged, erosional agents start their work on
it.
• Finally formation of ultimate featureless surface
For purpose of demonstrating his cycle, Davis imagined as an initial form a
mass of land uplifted from beneath the sea by earth movements

10. The Stage of Youth
The upliftment take place very rapidly
The process of denudation starts on a stable mass
If there is sufficient rain, a system of streams would quickly develop on the
newly emerged surface
The streams rapidly cut downwards and form deep valleys(“ V” shaped
valley)
Throughout the stage parts of the initial land surface would be preserved

11. Youth landscape Utah
river

12. The Stage of Maturity
Deepening of “V” shaped valley would have been slow down.
Channels become nearer and nearer to “The base level of erosion”.
Stream velocity would have been reduced.
Condition of Grade of equilibrium (entire energy is used for the movement
of water and its load).
Vertical erosion slows down and horizontal erosion become dominant
Gentle meanders, Flood plains

13. Mature
landscape,
Pennsylvania

14. The Stage of Old Age
Landscape evolution become extremely slow in operation.
Gradual reduction of river gradient, decline of stream energy and continued
lowering of angle of valley.
Continued to broaden their valley by meandering.
By the end of old stage relief would assume to form very gentle, termed by Davis
“Peneplain”
The remaining isolated hills above the peneplain referred as “Monadnocks”

15. Meandering: Amazon
river

16. Monadnock

19. REJUVENATION
May be caused by epirogenic upliftment of a landmass accompanying
tilting and warping.
World wide lowering of sea-level also causes rejuvenation
Knick point: The point of intersection of old and new base levels
Greater the stream speed also cases rejuvanation

23. GRAPH OF DAVICIAN CYCLE

24. Positive aspects of Davis model
Highly simple and applicable
Very simple expressive language
Based on detailed and careful field observations
Came long time after Hutton’s concept.
Capable of both predictions and historical interpretations

25. Negative aspects of Davis model
Rapid rate of upliftment.
Relationship between upliftment and erosion.
Long period of crustal stability not possible.
Dynamic equilibrium concept.
Based only on observation; no instrumentation and measurement.
Concept of grade not properly explained.

26. CONCEPT OF PENK
ON CYCLE OF
EROSION

27. Walter Penk
German Geomorphologist
Accepted the cycle of erosion
Main critic of Davisian cycle
Concept of phase, rate of uplift and degradation.
According to Penck, the characteristics of landforms of a given region
are related to the tectonic activity of that region.

28. The main postulates of Penks model,
• morphological characteristics of any region of the earth’s surface is
the result of competition between crustal movement and
denudation processes.
• Development of landscape is not time- dependent.
• Upliftment and erosion are always coexistent.

29. GRAPH OF PENKIAN CYCLE
Case Uplitment Absolute
height
Relative
relief
First Active Increases Increases
Second Active Increases Constant
Third Active Constant Constant
Fourth Finished Decreases Constant
Fifth Finished Decreases
rapidly
Decreases

30. There was certain misunderstanding in the interpretation of Penck’s
work as it was published in obscure German language.
Penck’s morphological system was severely criticised in the United
States in the same way the ‘geographical cycle’ was criticised in
Germany.
Penck’s concepts of parallel retreat of slope and continued crustal
movements were subjected to severe criticism by many
geomorphologists and geologists.
•

31. Davis cycle Penk's cycle
1. upliftment finished before Degradation starts. 1. upliftment and degradation strats together as soon as the
landmass comes above the sea level.
2. The period of upliftment is small. 2. The period of upliftment May long or small or
intermediately
3. The rate of uplift is very rapid. 3. different rate some times it is pride averge or slow also.
4. Landform is the result of structure , process and stage. 4. Landform is the result of the rate of uplift , rate of
degradation and there lation ship in between these tow.
5. the start and end of the cycle is associated with three
stages youth , mature and old.
5. He has not taken the stage into account but says three
conditions of upliftment
Aufsteigendo ( inereasing ) and geichformic (constant)
Andabsteigende ( decreasing).
6. daives has not given more importance to dlope. 6. penk has more important
Because it accelerates the rate of erosion and differentiate
the landform.
7. There five cases , In first case relief inereases , and in
second , third , and fourth it is constant and in the last fifth
one it decreases .
7. In his case in the first two stage relief increases out of his
three stage it decreases but never becomes constant .
8. Erosion does not exist in the first stage. 8. Erosion takes place in every stage and every cases .
9. He has assumed the last stage of cycle as the " peneplain " 9.He assumes the last stage as
" Endrumpf "
10. His cycle over humid areas 10. His cycle over arid areas

32. THEORY OF
L C KING

33. Based on his studies of landforms in arid, semi-arid and savanna
regions of South Africa.
He formulated a set of cyclic models (such as landscape cycle,
epigene cycle, pediplanation cycle, hillslope cycle, etc.) and asserted
that these are practicable in other parts of globe as well.
Major landscapes in all the continents have been evolved by rhythmic
global tectonic events.
King’s concept of upliftment and crustal stability is similar to the
concept of Davis.

34. Critique of Kings Model
King’s model was limited to the African experience.
 It is doubtful to assert that there is uniform development of
landscapes in different environmental conditions.

35. Gilbert’s Theory
Grove Karl Gilbert
“the landscape is the result of two competing tendencies i.e.
tendency towards variability (when driving force exceeds resisting
force) and tendency towards uniformity (when driving force equals
resisting force)”.
The three major components: concept of quantification, the concept
of time and the concept of equilibrium.

36. CONCLUSIONS
There is great difference between these two concepts developed by
Davis and penk.
Each concept is influenced by the landscapes of different regions.
No individual concept is sufficient to explain all kind of landforms.

37. References
Dr. Raad-Rahim hamood, cycle of erosion propounded by Davis and
Penk computerative study, AL-Faith Journal.
Chorley R. G. Beekinsal R P and dunnage(1973), the history of the
study of landforms, Methuen and company limited, London.
Thornbury W. D. (1969) Principle of Geomorphology , john wiley and
sons , Ine . Newyork , PP. 99-208.
Sparks B. W. (1972) Geomorphology , Longman Group Limited
London The Division Geography cycle , PP , 7-21
Woreester P . G (1958) text Book of Geomorphology , D. van
Nostrand company , Ine Newjercey , pp – 172 – 214