The document describes William Morris Davis' geographical cycle of erosion, which outlines the evolution of landforms over time through three main stages: youth, mature, and old. The cycle begins with the uplift of a landmass, initiating rapid erosion during the youthful stage as rivers deepen valleys. In the mature stage, erosion shifts to lateral widening of valleys as gradients decrease. Finally, in the old stage valleys become flat as erosion slows, resulting in a peneplain landscape. The cycle may be rejuvenated by drops in sea level or renewed uplift restarting the erosion process.

1. GEOGRAPHICAL CYCLE OF EROSION
• WILLIAM MORRIS DAVIS(1850-1934)
• BASIC CONCEPT OF ‘ SEQUENTIAL CHANGE IN LANDFORMS THROUGH
TIME LIKE EVOLUTION OF AN ORGANIC LIFE.’
• THREE STAGES: YOUTH, MATURE AND OLD
• DEFINITION: GEOGRAPHICAL CYCLE IS THE PERIOD OF TIME DURING
WHICH AN UPLIFTED LANDMASS UNDERGOES ITS TRANSFORMATION BY
THE PROCESS OF LAND SCULPTURE ENDING INTO A LOW FEATURELESS
PLAIN-A PENEPLANE.
• ACCORDING TO DAVIS: THREE FACTORS – STRUCTURE, PROCESS AND TIME
play important roles in origin and development of landforms of a particular
place.

2. Trio of Davis
• “ landscape is a function of structure, process and time.”
• Stages of erosion

3. Stages of erosional cycle
• cycle of erosion begins with the upliftment of landmass. There is
a rapid rate of short-period upliftment of landmass of homogeneous
structure. This phase of upliftment is not included in the cyclic
time as this phase is, in fact, the preparatory stage of the cycle
of erosion.
• The above figure represents the model of geographical cycle
wherein UC (upper curve) and LC (lower curve) denote the hill-tops
or crests of water divides (absolute reliefs from mean sea level)
and valley floors (lowest reliefs from mean sea level)
respectively.
• The horizontal line denotes time whereas vertical axis depicts
altitude from sea level. AC represents maximum absolute relief
whereas BC denotes initial average relief. Initial relief is
defined as difference between upper curve (summits of water
divides) and lower curve (valley floors) of a landmass. In other
words, relief is defined as the difference between the highest and
the lowest points of a landmass. ADG line denotes base level which
represents sea level. No river can erode its valley beyond base
level (below sea level).
• Thus, base level represents the limit of maximum vertical erosion
(valley deepening) by the rivers. The upliftment of the landmass

4. Youthful stage
• Now erosion starts and the whole cycle pass through the following
three stages:
• Erosion starts after the completion of the upliftment of the
landmass. The top surfaces or the summits of the water divides are not
affected by erosion because the rivers are small and widely spaced. Small
rivers and short tributaries are engaged in head-ward erosion due to
which they extend their lengths. The process is called stream lengthening
(increase in the lengths of the rivers).
• Because of steep slope and steep channel gradient rivers actively deepen
their valleys through vertical erosion aided by pothole drilling and thus
there is gradual increase in the depth of river valleys. This process is
called valley deepening. The valleys become deep and narrow characterized
by steep valley side slopes of convex plan.
• The youthful stage is characterized by rapid rate of vertical erosion and
valley deepening because:
• The channel gradient is very steep,
• Steep channel gradient increases the velocity and kinetic energy of the river flow,
• Increased channel gradient and flow velocity increases the transporting capacity of
the rivers,
• Increased transporting capacity of the rivers allows them to carry big boulders of
high calibre (more angular boulders) which help in valley incision (valley deepening
through vertical erosion) through pothole drilling.

5. Mature stage
• The early mature stage is heralded by marked lateral
erosion and well integrated drainage network. The graded
conditions spread over larger area and most of the
tributaries are graded to base level of
erosion. Vertical erosion or valley deepening is
remarkably reduced. The summits of water divides are
also eroded and hence there is marked fall in upper
curve (UC) i.e., there is marked lowering of absolute
relief.
• Thus, absolute relief and relative relief, both
decrease. The lateral erosion leads to valley widening
which transforms the V-shaped valleys of youthful stage
into wide valleys with uniform or rectilinear valleys
sides. The marked reduction in valley deepening
(vertical erosion or valley incision) is because of
substantial decrease in channel gradient, flow velocity
and transporting capacity of the rivers.

6. Old stage
• Old stage is characterized by almost total absence of valley
incision but lateral erosion and valley widening is still
active process. Water divides are more rapidly eroded. In
fact, water divides are reduced in dimension by both, down-
wasting and back-wasting. Thus, upper curve falls more
rapidly, meaning thereby there is rapid rate of decrease in
absolute height. Relative or available relief also decreases
sharply because of active lateral erosion but no vertical
erosion. Near absence of valley deepening is due to extremely
low channel gradient and remarkably reduced kinetic energy and
maximum entropy.
• The valleys become almost flat with concave valley side
slopes. The entire landscape is dominated by graded valley-
sides and divide crests, broad, open and gently sloping
valleys having extensive flood plains, well developed
meanders, residual convexo-concave monadnocks and extensive
undulating plain of extremely low relief. Thus, the entire
landscape is transformed into peneplain. As revealed by fig.
the duration of old stage is many times as long as youth and
maturity combined together.

8. NORMAL CYCLE OF EROSION
• The cycle of erosion which is carried by
running water is known as normal cycle of
erosion. This is because running water or
fluvial processes are most widespread all over
the world. It plays an important role in the
regions of glacial and arid.
• The normal cycle of erosion begins when a landmass
gets uplifted in accordance with the sea level. As
the land gets uplifted, the rivers get originated
and erosional processes begin thereafter. After some
duration of time the upliftment of the landmass
stops resulting in erosional processes to be more
active.

9. YOUTHFUL STAGE
• This stage gets originated when the landmass gets
uplifted. The streams are short in length and number.
The master consequent streams get originated in very few
numbers.
• Several gullies and rills dominate the slopes. Through
headward erosion gullies and rills lengthens their
longitudinal profile.
• The development of the tributaries from the master
consequent streams, gives rise to dendritic drainage
pattern.
• The valleys are experienced through rapid rate of
downcutting by the rivers. This is because the
transporting capacity of rivers becomes high due to
steep channel gradient.
• The valleys become narrow and steep having convex side
slopes. This result in the juvenile valleys to be V-
shaped.

10. MATURE STAGE
• This stage is characterized by a decrease in the valley
deepening from the youthful stage, which results in a
decrease in channel gradient and flow velocity.
• Early maturity gets arrived which is indicated by a
decrease in the transporting capacity, decrease in the
channel gradient and a decrease in the river velocity.
• Valley widening becomes dominant at this stage, through
an active rate of lateral erosion.
• Big boulders and sediments are deposited by the rivers
at the foothill zones, due to the decrease in the
transporting capacity of the rivers. The deposition of
these materials results in the formation of alluvial
fans and cones, which further results in the formation
of piedmont plains due to their gradual expansion.
• As there is decrease in the channel gradient, the rivers
carve their courses resulting in the formation of
several meanders and loops.

11. OLD STAGE
• This stage is characterized by more decrease in the
channel gradient and there is the total absence of
valley deepening.
• There is a decrease in the number of tributary streams.
Moreover, the valleys become broad and flat comprising
of concave slopes.
• The transporting capacity of the rivers becomes low at
this stage. Sedimentation and weathering become more
active.
• Rivers carves their courses to an extreme form and forms
extensive deltas at the mouth of the rivers.
• At this stage, the landscape gets transformed into
extensive flat plains which are known as a peneplain.
•

12. REJUVENATION
• ACCELERATION OF EROSIVE POWER OF THE FLUVIAL PROCESS
(RIVERS) CAUSED BY MANY FACTORS.
• LENGTHENS THE PERIOD OF CYCLE OF EROSION
• CAUSED EITHER DUE TO SUBSTANTIAL FALL IN SEA LEVEL OR DUE TO
UPLIFTMENT OF LANDMASS
• DRIVEN BACK TO YOUTHFUL STAGE CHARACTERIZED BY STEEP
CHANNEL GRADIENT AND ACCELERATED VALLEY INCISION.