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:

●Understanding the relationship between landforms and different geologic factors (such as structure, lithology, climate, ……., etc.

●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.

GEOMORPHOLOGYLect. No. 1

Definition of geomorphology and some fundamental concepts in geomorphology.

13 / 10 / 2014

◙ Lecture contents: ●Definition of geomorphology → As a word and As a science. ●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”.

●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. 

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 in geomorphology:

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.

Some fundamental concepts are enumerated by W.D. Thornbury which comes into use in the interpretation of landscapes. The concepts are:

3-Stream action in valley has the same intensity in the past and 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.

Example of mass wasting

Grand Canyon

,

Wave action and water chemistry

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:

d-permeability or impermeability of rocks.

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.

Concept (3):

To a large degree the earth surface possess relief because the geomorphic processes operate at differential rates.

a-lithology and structure are major factors causing differential wasting of the earth surface.

Explanation:

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.

C/ Moraines are produced by glaciers.

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.

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 evolution is more common than simplicity.

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.

The geologic structures are in general much older than topographic features developed upon them except in area of late Pleistocene and recent diastrophism.

Explanation:

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.

The climatic factors especially precipitation and temperatures influence the operation of the geomorphic processes.

Explanation:

Concept (10): Geomorphology although concerned primarily with present-day landscapes attains its maximum usefulness by historical extension.

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.

Explanation:

Concept Description AlternativesUnusual processes without modern analogs occurred in the geologic past.

Similar geomorphic processes that operate today operated throughout geologic time.

Uniformitarianism

Cataclysmic processes and changes are most important in landscape evolution.

Relatively frequent, modest-sized processes dominate in the progressive changing of the landscapes over long time periods.

Gradualism

Some landscapes arise from disorderly processes.

Erosional agents on a planetary surface produce an orderly sequence of landforms as a function of time.

Orderliness

Geologic structure predominates over climate in influencing landform assemblages.

Landscapes reflect the influence of certain climatic processes by developing a characteristic assemblage of landforms.

MorphoclimaticZonation

In stable tectonic areas, extensive landscapes of Tertiary, or even Mesozoic, age are preserved

Most of the Earth´s topography is no older than Pleistocene.

Youthfulness ofTopography

Relict landscape elements persist despite Pleistocene changes and comprise palimpsests

The geologic and climatic changes of the Pleistocene were critical in the shaping of most landscapes.

Legacy of the Pleistocene

Geomorphology attains its maximum usefulness by historical extension, analyzing ancient conditions.

Geomorphology is primarily concerned with present- day processes that shape present-day landscapes.

Modernism

Complexity of geomorphic systems is more common than Simplicity.

It is necessary to search for simplicity in geomorphological systems.

Simplicity

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؟؟؟؟؟ قورسه خوا وا به!!!!!نـييـه

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