THEORY of GEOMORPHOLOGY
2014 --- 2015
• Dr. Azhar Kh. S. Bety
Lecture duration: (2 hours)
Lecturer members:
-Theory : Dr. Azhar Kh. S. Bety
-Practice: Dr. Azhar Kh. S. Bety & Ms. Lanja
References:
1-Thornbury, W. D., 1969. Principles of geomorphology (2nd ed.).
John Wiley & Sons, Inc., New York, 594p.
2-Bloom, A. L., 2002. Geomorphology- A systematic analysis of Late
Cenozoic landforms (3rd ed.). Prentice-Hall of India Private Limited,
New Delhi, 482p.
3-Ritter, D. F., 1986. Process geomorphology (2nd ed.). Wm. C.
Brown Publishers, lowa, USA, 579p.
4-Spark, B. W., 1972. Geomorphology (2nd ed.). Longman Group Ltd,
London, 530p.
5-Blyth, F. G. H. & de Freitas, M. H., 1974. A geology for engineers
(6th ed.) Edward Arnold, London, 557p.
6-Gribble, C. D., 1985. Geology for civil engineers (2nd ed.). George
Allen & Unwin, London, 314p.
7-Strahler, A & Strahler, A., 2002. Physical geography (2nd ed.). John
Wiley & Sons, Inc, USA, 748p.\
8- FUNDAMENTALS OF GEOMORPHOLOGY. Second Edition.Richard
John Huggett. Taylor & Francis e-Library, 2007..483P.
Objectives of Geomorphology:
●Identification of different types of landforms, like valley, ridges,
flood plains, alluvial fans, deltas, karst topography, scarps, sand
dunes, moraines,…….,etc.
●Identification of the different geomorphic processes and agents
which are responsible in the formation of its own landforms.
●Understanding the relationship between landforms and different
geologic factors (such as structure, lithology, climate, ……., etc.
GEOMORPHOLOGY
Lect. No. 1
13 / 10 / 2014
Definition of geomorphology and some fundamental
concepts in geomorphology.
◙ Lecture No.(1):
Definition of geomorphology and some fundamental
concepts in geomorphology
◙ Lecture duration: (2 hours)
◙ Objectives of the lecture:
●Identification of the geomorphology science.
●Understanding some fundamental concepts in
geomorphology which they will aid in the evaluation of
much that follows in the subject “geomorphology”.
◙ Lecture contents:
●Definition of geomorphology → As a word and As
a science.
●Some fundamental concepts in geomorphology:
●Definition:
•As a word, geomorphology is composed of three
Greek roots which are “Geo, Morph & Logy” that mean
the “Earth, Form & Science” respectively.
●As
a science, geomorphology is one of the
branches of geology, dealing with the study of
landforms of the earth, including submarine forms
also, their formation, developments and relation to the
other geological factors.
Geomorphology is the scientific study of landforms and
the processes that shape them.
Geomorphology, studies in particular the lithosphere,
and interactions with the atmosphere and hydrosphere,
to understand the interconnection of various system
processes.
Geomorphologists are particularly interested in the
potential for feedbacks between climate and
tectonics mediated by geomorphic processes.
Geochronology, uses dating methods to measure the
rate of changes. Terrain measurement techniques,
include differential GPS, remotely sensed digital terrain
models and laser scanning, to quantify, study, and to
generate illustrations and maps.
Initially, the subject was concerned with unravelling the
history of landform development, but now it is also
concerned with understanding the processes which
create landforms and how these processes operate.
Geomorphology is the study of landforms and
landscapes, including the description, classification,
origin, development, and history of planetary surfaces.
●Some fundamental concepts in geomorphology:
They are a number of concepts will aid in the
evaluation of much that follows in the subject
“geomorphology", but also not only ones used in the
interpretation of the landforms (landscapes).
Some fundamental concepts are enumerated by W.D.
Thornbury which comes into use in the interpretation of
landscapes. The concepts are:
Concept (1):
The same physical processes and laws that operate
today, operated throughout geologic time, although not
necessarily always with the same intensity as now.
Explanation:
1-It is the principle of ‘uniformitarianism’, which states
that ‘the present is the key to the past‘.
2-Tectonic activities, climate, glaciers for example
prove that the processes are not the same intensity.
3-Stream action in valley has the same intensity in the
past and now.
Example of mass wasting
Wave action and water chemistry
Grand Canyon,
Concept (2):
Geologic structure is a dominant control factor in the
evolution of landforms and is reflected in them.
It is including such phenomena as:
a- rock attitude (dip and strike).
b- presence or absence of joints, faults, folds and
bedding planes.
c-physical hardness of
the constituent of mineral.
d-permeability or
impermeability of rocks.
Concept (3):
To a large degree the earth surface possess relief
because the geomorphic processes operate at
differential rates.
Explanation:
a-lithology and structure are
major factors causing
differential wasting of the
earth surface.
b-temperature,
moisture,
altitude,
exposure,
topography configuration, the amount and type of
vegetation cover are factors causing changes in
geomorphic processes within narrow limits.
c- variation in the climate condition between a
(valley floor and hill top), (bare ground and hay
vegetable cover) may be reflected the:
•Amount of precipitation
•Rate and type of evaporation
•Amount of soil moisture
•Temperature fluctuation above and
below the freezing line.
These factors cause and make the geomorphic
processes to operate at different rates and types at least
within limited area.
•Except for region of very recent diastrophism one can
say or assume safely that:
A/ high topographic area are underlain by hard rocks.
B/ low topographic area are underlain by weak rocks.
Concept (4):
Geomorphic processes leave their distinctive imprint
upon landforms and each geomorphic process develops
its own characteristic assemblage of landforms.
Explanation:
•landforms have their individual distinguishing features
depending upon the geomorphic processes responsible
for their development, for example:
A/ flood plains. Alluvial fans and deltas are products
of stream action.
B/ Sinkholes and cavern are produced by ground
water.
C/ Moraines are produced by glaciers.
Concept (5):
As the different erosional agents act upon the earth
surface, there is produced an orderly sequence of
landforms..
Explanation:
•Davis stressed his concept of geomorphic cycle and its
stages of (young, mature and old) depending upon that
landforms posses distinctive characteristics.
•Most geomorphologist belive that “landforms” have an
orderly and sequential development but not all belive
that the stages (young, mature and old) have reality.
•A corollary to the concept of completed geomorphic
cycle; is that of a partial cycle is accepted as a concept.
•In fact the partial cycle are far more likely to occur than
completed cycle because most of the earth crusts are
subjected to intermittent and differential uplift.
Concept (6):
Complexity of geomorphic
common than simplicity.
evolution
is
more
Explanation:
*Little of the earth topography can be explained as the
result of the operation of the single geomorphic process
or cycle of development.
*It is rare to find landscape
assemblage which can be
attributed solely to one
geomorphic process.
Concept (7):
Little of the earth topography is older than Tertiary
and most of it no older than Pleistocene.
Explanation:
The geologic structures are in general much older than
topographic features developed upon them except in
area of late Pleistocene and recent diastrophism.
Concept (8):
Proper interpretation of present day landscapes is
impossible without a full appreciation of the manifold
influences of the geologic and climatic changes during
the Pleistocene.
A- glaciation directly affected many million square miles.
B- the glaciation effect extended far beyond the areas
actually glaciated.
Concept (9):
An appreciation of world climates is necessary to a
proper understanding of the varying importance of the
different geomorphic processes.
Explanation:
The
climatic
factors
especially precipitation and
temperatures influence the
operation of the geomorphic
processes.
Concept (10):
Geomorphology although concerned primarily with
present-day landscapes attains its maximum usefulness
by historical extension.
Explanation:
A-Geomorphology deals with the present-day
landscapes that date back to previous epochs and
periods.
B- Geomorphologist should adobt historical approach
especially by application of the principle of
Uniformitarianism.
Alternatives
Description
Concept
Uniformitarianis
m
Similar geomorphic processes that operate today Unusual
processes
without
modern analogs occurred in the
operated throughout geologic time.
geologic past.
Gradualism
Relatively frequent, modest-sized processes Cataclysmic
processes
and
dominate in the progressive changing of the changes are most important in
landscapes over long time periods.
landscape evolution.
Orderliness
Erosional agents on a planetary surface produce an Some landscapes arise
orderly sequence of landforms as a function of disorderly processes.
time.
from
Morphoclimatic
Zonation
Landscapes reflect the influence of certain climatic Geologic structure predominates
processes by developing a characteristic over climate in influencing
assemblage of landforms.
landform assemblages.
Youthfulness of
Topography
Most of the Earth´s topography is no older than In stable tectonic areas, extensive
landscapes of Tertiary, or even
Pleistocene.
Mesozoic, age are preserved
Legacy of the
Pleistocene
The geologic and climatic changes of the
Pleistocene were critical in the shaping of most
landscapes.
Relict landscape elements persist
despite Pleistocene changes and
comprise palimpsests
Modernism
Geomorphology is primarily concerned with
present- day processes that shape present-day
landscapes.
Geomorphology attains its
maximum usefulness by historical
extension, analyzing ancient
conditions.
It is necessary to search for simplicity in
Complexity of geomorphic
Simplicity
‫ئه مه جى يه كه م موحازه ره يه ئه ويه؟؟؟‬
‫به خوا قورسه ؟؟؟؟؟‬