- Peneplanation is the process of peneplaining a land surface, i.e. eroding it to become a large area of low relief through processes of erosion, e.g. the area surrounding Ayers Rock, Australia.
- peneplanation in the dictionary is the act or an instance of producing a relatively flat land surface by a long period of erosion.
- peneplanation in the dictionary is the act or an instance of producing a relatively flat land surface by a long period of erosion.
PENEPLAIN
Peneplain is the term coined by W.M. Davis to
mean a surface of low relief worn down to near
sea level and formed through erosion over protracted
spans of time. His own words are:
Given sufficient time for the action of denuding
forces on a mass of land standing fixed with
reference to a constant base-level, and it must
be worn down so low and so smooth, that it
would fully deserve the name of a plain. But it
is very unusual for a mass of land to maintain
a fixed position as long as is here assumed. . . .
I have therefore elsewhere suggested that an old
region, nearly base-levelled, should be called an
almost-plain; that is a peneplain.
(Davis in Chorley et al. 1973: 190)
The peneplain is thus not the end-product of a
cycle of erosion and, if keeping with Davis’s way
of thinking, it should not be confused with an
endless and featureless plain as is often implied.
Peneplain is the term coined by W.M. Davis to
mean a surface of low relief worn down to near
sea level and formed through erosion over protracted
spans of time. His own words are:
Given sufficient time for the action of denuding
forces on a mass of land standing fixed with
reference to a constant base-level, and it must
be worn down so low and so smooth, that it
would fully deserve the name of a plain. But it
is very unusual for a mass of land to maintain
a fixed position as long as is here assumed. . . .
I have therefore elsewhere suggested that an old
region, nearly base-levelled, should be called an
almost-plain; that is a peneplain.
(Davis in Chorley et al. 1973: 190)
The peneplain is thus not the end-product of a
cycle of erosion and, if keeping with Davis’s way
of thinking, it should not be confused with an
endless and featureless plain as is often implied.
Rather, a peneplain is a regional landscape at the
penultimate stage of development which is yet to
be eroded down to a true plain. In another place
Davis himself says:
At a less advanced stage of degradation, the
land will still possess low, unconsumed hills
along the divides and subdivides between the
broad-floored rivers. It will then be almost-aplain,
or a peneplain. A peneplain will be
hardly above sealevel at its base, but if the area
is large it may attain altitudes of 2,000, 3,000,
or 4,000 feet far inland near the river heads,
and its residual mounts and hills may rise still
higher, although with gentle slopes.
(Davis in King and Schumm 1980: 8)
The processes leading to a peneplain would be
mainly subaerial, chiefly fluvial and gravitydriven
hillslope processes. They ought to be in
action long enough to obliterate the effect of
unequal rock resistance, so only the hardest rocks
would form bedrock-built hills rising above the
peneplain, the monadnocks. Otherwise, gentle
slopes would be underlain by deeply weathered
rock, with the thickness of weathering mantle
being in excess of 10 m. As far as the relative
relief of a peneplain is concerned, Davis seemed
to be rather vague in defining any critical hill
heights or slope angles. Therefore, there are two
crucial characteristics of a peneplain. One is its
temporal context within the cycle of subaerial
erosion. To be a peneplain, the surface of low
relief must have formed in the course of protracted
denudation. The second prerequisite is
grading down to sea level.
Much of the substantial confusion around the
term results from the fact that subsequent workers
did not always keep with Davis’s original
definition and used the term in various contexts.
For example, peneplains were often equated with
PLANATION SURFACEs, or a particular mode of slope
evolution was implied for a peneplain. Many geomorphology
textbooks contrast peneplains
formed mainly through slope downwearing and
consequent relief reduction, with pediplains
formed by slope backwearing and relative relief
maintained high until a rather late stage of development.
In other cases the condition of being
located close to, or graded to, sea level was
ignored. In consequence, flattened summit surfaces
within mountain ranges were frequently
called peneplains despite the fact that neither their
origin nor the age were known sufficiently to warrant t
penultimate stage of development which is yet to
be eroded down to a true plain. In another place
Davis himself says:
At a less advanced stage of degradation, the
land will still possess low, unconsumed hills
along the divides and subdivides between the
broad-floored rivers. It will then be almost-aplain,
or a peneplain. A peneplain will be
hardly above sealevel at its base, but if the area
is large it may attain altitudes of 2,000, 3,000,
or 4,000 feet far inland near the river heads,
and its residual mounts and hills may rise still
higher, although with gentle slopes.
(Davis in King and Schumm 1980: 8)
The processes leading to a peneplain would be
mainly subaerial, chiefly fluvial and gravitydriven
hillslope processes. They ought to be in
action long enough to obliterate the effect of
unequal rock resistance, so only the hardest rocks
would form bedrock-built hills rising above the
peneplain, the monadnocks. Otherwise, gentle
slopes would be underlain by deeply weathered
rock, with the thickness of weathering mantle
being in excess of 10 m. As far as the relative
relief of a peneplain is concerned, Davis seemed
to be rather vague in defining any critical hill
heights or slope angles. Therefore, there are two
crucial characteristics of a peneplain. One is its
temporal context within the cycle of subaerial
erosion. To be a peneplain, the surface of low
relief must have formed in the course of protracted
denudation. The second prerequisite is
grading down to sea level.
Much of the substantial confusion around the
term results from the fact that subsequent workers
did not always keep with Davis’s original
definition and used the term in various contexts.
For example, peneplains were often equated with
PLANATION SURFACEs, or a particular mode of slope
evolution was implied for a peneplain. Many geomorphology
textbooks contrast peneplains
formed mainly through slope downwearing and
consequent relief reduction, with pediplains
formed by slope backwearing and relative relief
maintained high until a rather late stage of development.
In other cases the condition of being
located close to, or graded to, sea level was
ignored. In consequence, flattened summit surfaces
within mountain ranges were frequently
called peneplains despite the fact that neither their
origin nor the age were known sufficiently to warrant t
he use of the term in its strict, Davisian
sense. Davis himself suggested the term ‘pastplain’
to describe a peneplain which has been uplifted
and now shows the initial stage of dissection.
Free usage of the term and its obvious connection
with the Davisian model of cyclic landform
development and the DENUDATION CHRONOLOGY
approach, themselves strongly criticized since the
1960s, had eventually led to its declining popularity
and gradual abandonment. Preference was
given to more neutral ‘planation surfaces’ in
describing landscapes, whereas in the field of theory
a search for non-cyclic models of geomorphic
development was pursued strongly.
sense. Davis himself suggested the term ‘pastplain’
to describe a peneplain which has been uplifted
and now shows the initial stage of dissection.
Free usage of the term and its obvious connection
with the Davisian model of cyclic landform
development and the DENUDATION CHRONOLOGY
approach, themselves strongly criticized since the
1960s, had eventually led to its declining popularity
and gradual abandonment. Preference was
given to more neutral ‘planation surfaces’ in
describing landscapes, whereas in the field of theory
a search for non-cyclic models of geomorphic
development was pursued strongly.
_______________________________________________________________________
Sources:
Encyclopedia of Volume - Andrew S. Goudie
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