Geomorphology

Waqar S/O Mohammad Pannah Ghanghro. Student of BS-Part I Geology. Batch no: 2k13/GLG/162. Teacher name: Qamar-u-din Khokhar District: Larkana. Contact no# 0303-2828135.

Introduction of geomorphology. Definition of geomorphology. Agents of geomorphology. Land-form/Land-scape. Forces of land-forms. Sources of force for land-forms. Processes of land-form. Types of land-form. Basic concepts of geomorphology.

Geomorphology

Introduction to geomorphology:

The word geomorphology has been taken from Greek Language (Geo means Earth) + (morph means shape) + (logy means Study) so the literal meaning of Geomorphology is the study about the shapes on the earth.

Geo=Earth, Morph=Shape=Land-forms=Process.

“Geomorphology is the study of Land-forms and the Land-scape, including the description classification, origin, development and history of (Planetary) surfaces; during the early part of this century, the study of regional-scale geomorphology was termed as “Physiography”. Unfortunately, physiography also became synonymous with (physical geography).

There are many scientists who have contributed on the geomorphology; among them two are the most famous

1. James Hutton: He gave the Principle of uniformatarism; he said that Present is the key of Past.

2. William Morris Davis: He gave the sequence of land-forms.

Young stage + mature stage + Old stage

Definition: It is the branch of Geology which gives the study about Land-forms, Land-scape and various processes that produced these Landforms.

Land-form: Land-form is a individual feature on the surface of the earth.

Land-scape: Land-scape is the combined effect of numerous/various land-forms.

Geomorphology is the systematic study of land-forms.

Geomorphic Agents:

River, Wind, Glacier and Sea-water.

These geomorphic agents basically serves four functions;

1) Weathering.

2) Erosion.

3) Transportation.

4) Deposition.

Weathering: The breaking-down of the rocks under the influence of atmosphere, climate and the elements of weather is known as weathering.

Agents of weathering:

Mechanical /Physical weathering. Chemical weathering.

Mechanical/Physical weathering: The process of weathering by which physical forces break down or reduce a rock to smaller and smaller fragments, involving no chemical change is known as physical weathering.

Types f mechanical/physical weathering.

Frost wedgingCrystal growthThermal expansion/ContractionMechanical exfoliationAbrasionPlantation and Human activities

Chemical weathering: A weathering process whereby rocks and minerals are transformed into new, fairly stable chemical combinations by such chemical reactions as hydrolysis, oxidation, ion exchange, and solution is known as chemical weathering.

Types of chemical weathering.

Dissolution HydrolysisOxidation

Erosion: The removal of braked rock- fragments and particles by wind, water, glacier andGravitational forces are known as erosion.

Agents of erosion:

WindWaterGlacierGravitational forces

Transportation: The braked rock-fragments and particles from place to palace (shifted by the agents) are known as transportation. Agents of transportation

WindWaterGlacier/IceGravitational forces

Deposition: The settling of the braked rock-fragment/particles shifted and deposited is known as deposition. Agents of deposition:

WeatheringErosion

“Each geomorphic agent functions in a way peculiar to it and as a result produces erosional and depositional land-forms which are characteristic of that agent.”

Land-form: Land-form is an individual feature on the surface of the earth; Landforms are created by different forces of nature.

For example, Mountains, Oceans, Valleys and deserts can be called landforms.

Land-form (a) Land-form (b)

Land-scape: The group of land-forms is called land-scape.

OR

The combined effect of numerous/various land-forms is known as land-scape.

Land-scape

Study of land-forms includes.

Origin(shows the key to the past)Evolution(Modification)Shape(The shape of land-form)Process(Rain, Wind, Tectonic process,

Denudation process, Gravity process)

Land-forms are created by natural forces these forces are:

Endogen tic force(is that force which cause movements beneath of the Earth's surface)

For example: Earthquakes, Plate tectonics

Exogenesis force (The process which are originates outside of the earth’s crust are called exogenesis force.)

For example: Weathering, Erosion, Mass wasting.

Sources of force/energy for land-forms:

Interior of earth

Sun

Interior of earth: “The forces which are operating on the land-forms are comes up from the interior of the earth, earth is divided into three layers.”1. Crust2. Mantle3. Core Core is the hottest layer of the earth, the temperature at core is about to 7000 centigrade whatever the material is present at core its density becomes low due to high temperature it starts to escape and when the material trying to come up on the surface of the earth atmospheric temperature/pressure cools it and it comes down and make a convection current due to convection

current the plate-tectonics moves in that result land-forms/land-scape takes place on the earth surface.There are three types of plate-tectonics1. Convergent (due to convergent mountains are formed)2. Divergent (due to divergent mid-oceans, rifts are formed)3. Transformation (due to transformation earthquakes takes place.)

Sun: Sun is a star which emits the light and light comes on the surface of the earth, it warms the earth features and in that result the hotter place trying to up, when it comes up the atmospheric temperature/pressure cools it and it comes down and make a convection current and some material removes from that site and make land-forms/land-scapes.

Process of land-forms:

Eolian process Fluvial process Glacier process Ground water process Coastal process

Eolian process: Eolin process is created by the geological action of wind and it is divided into three stages:1. Erosion2. Transportation3. Deposition

Erosion shows clearly itself in three ways.

1. Abrasion2. Deflation 3. Attrition

1. Abrasion: Abrasion is the sand blast action of wind with sand against the rocks. The loose particles that are blown (blow) away by the wind serve as tool of destruction and when they move on some rock-surface they bring about a scraping (damage) of the surface.

2. Deflation: The lifting and removal of loose material from the earth’s surface.

3. Attrition: Attrition is the grinding action while on transit wind born particles often collide with one another. Such mutual collision brings about a further grinding of the particles.

Important Erosional features and associated land-forms:

a. Hamada: Due to deflation, when the loose particles are swept away, only the hard mantle is left behind which is known as Hamada.

b. Yardang: A grooved topographic form produced by wind abrasion, which is in elongated in the direction of prevailing winds and is usually strongly under cut, is known as Yardang.

c.Pedestal rock: A wide rock-cap standing on a slender rock column, produced because of the wind-abrasion, is known as a Pedestal rock.

Transportation: Wind-transportation is totally dependent on wind-velocity.

Methods of wind-transportation:

a. Traction: Where particles are removed through rolling and creeping.

b. Suspension: Very light particles like dust and cloud, smoke etc move with wind quickly but settle very slowly, remain in suspension in the air.

c. Saltation: The particles which are too heavy to remain in suspension and lighter to be transported in traction are transported through a series of bounces.

Fluvial process:

Fluvial process is the physical interaction of flowing water and the natural channels of rivers and streams. Rivers and streams eroded, transported and deposited the material.

Glacial process: Glacial is a climatic accident and climate gets very cold and the rivers freezes and water becomes ice is known as glacial.

Types of glacier

There are three major types of glacier.

1. The valley glaciers (Mountain or Alpine glaciers)

2. Piedmont glaciers: These glaciers are the intermediate in form and origin between valley glaciers and ice-sheets. They are formed at the foot of the mountain.

3. Ice-sheets: These are the huge covers of ice and are also known as “continental glaciers.”

Ground water process:

Ground water is that part of the sub-surface which fully saturates the pore-spaces (little holes in earth) Small holes/poles into the earth by which water absorbed in to the pores and conserved into the subsurface of the earth.

Coastal process:

There are three types of land-form.

1. Structural land-form: Structural land-forms are produced by the movement of plate-tectonics.

2. Weathering land-form: Weathering land-forms are produced by

3. Erosional land-form:

When the

4. Depositional land-form:

Concept 1:

The same physical process and laws which are operating today they were also operated throughout geological time although not necessarily always with same intensity. This concept was given by James Hutton in 1785 and it is also known as principle of uniformatarism (present is the key of past.)

Concept 2: “Geological structures are the dominant control factor in the evolution of land-form and are reflected in them.”

Structures are developing in lithosphere

“This concept tells that the geological structures are the key factors for forming land-forms/land-scapes.”

Geological structures are:

Fold Fault Joint

Bedding planesunconformity

Concept 3: To a large degree the earth surface posse’s relief because the geomorphic process operate at different rate.

“This concept tells that the geomorphic processes are varying at the earth with its different rates that is why earth is in relief.”

Relief=Elevation + Depration

Hard rock’s make Elevation and soft rocks make Depration.

Concept 4: Geomorphic processes leave their distinctive/characteristic imprints upon land-forms and each geomorphic process develops its own characteristic assembling (group) of land-form.

Concept 5: The different erosional agents act upon the earth surface and produced any orderly sequence of landform.

“This concept tells about the sequence of land-forms”

Like a river its sequence shall be as according to geomorphology:

Initial stage + Young stage + mature stage + Old stage.