Feeds:
Posts
Comments

Landform, whether large or small result from the interaction of certain forces, they accomplish their work by various means of processes, which may be described as geologic, Climatic and biologic and these processes bring about the changes in the Earth’s surface which may be Classified as (I) Long Period Changes (Man Is unable to notice this change) and (II) short period Changes. The forces which affect the crust of the earth are broadly classified in two types

  • ENDOGENETIC FORCE-ORIGINATES FROM WITHIN THE EARTH
  • EXOGENETIC FORCE-ORGINATES FROM WITHOUT,OR BEYOND THE EARTH

ENDOGENETIC FORCES

The forces coming from within the earth are called as Endogenetic forces which causes two types of movement in the earth viz (I) Horizontal movements (II) Vertical movements. These forces derive their energy from changes such as radioactivity, chemical recombination, expansion or contraction or displacement of molten materials which Occurs in the interior of the earth. This group of forces may be called as Tectonic forces which manifests through Processes Called Diastrophism and Volcanism. The origin of Endogenetic forces and related horizontal and vertical movements are caused due to contraction and expansion of rocks because of varying thermal conditions and temperatures inside the earth. Volcanic eruptions and seismic events are also expressions of Endogenetic forces. The displacement and readjustment of geomaterials sometimes take place so rapidly that earth’s movements are caused below the crust. On the basis of intensity the Endogenetic forces and movements are divided in to two major Categories

  1. SUDDEN FORCES
  2. DIASTROPHIC FORCES

SUDDEN FORCES AND MOVEMENT

Sudden and become disastrous When they occur in densely populated localities. These forces work very quickly and their results are seen within minutes. Movements, caused by sudden-Endogenetic forces coming from deep within the earth cause sudden and rapid events that cause massive destructions at and below the earth’s surfaces. Such events like volcanic eruptions and earthquakes, are called ‘EXTREME EVENTS’ and become disastrous hazards when they occur in densely populated localities. These forces work very quickly and their results are seen within minutes. ‘It is important to note that these forces are the result of long period Preparation. Only their cumulative effects on the earth’s surface are quick and sudden.’ Geologically, these sudden forces are termed as ‘constructive forces’ because these create certain relief features on the earth’s surface. For example, volcanic eruptions result in the formation of volcanic cones and mountains while fissure flows of lavas form extensive lava plateau and lava plains Earthquakes create faults, fractures, lakes etc.

Figure 1 Deccan Plateau in India

Figure 2 Columbia Plateau in USA

Diastrophic Forces and Movements

Diastrophic forces include both vertical and horizontal movements which are caused due to forces deep within the earth. These diastrophic forces operate very slowly and their effects become discernible after thousands and millions of years. These forces are also termed as constructive forces, affect large areas of earth and produce meso-level reliefs such as mountains, Plains, Plateaus, lakes, big faults etc. These diastrophic forces and movements further subdivided in to

  1. EPEIROGENETIC MOVEMENTS
  2. OROGENETIC MOVEMENTS

EPEIROGENETIC MOVEMENTS

Epeirogenetic movement causes upliftment and subsidence of continents masses through upward and downward movements respectively. Both, the movements are in fact vertical movements. These are further divided in to

  1. Upward Movement
  2. Downward Movement

Upward Movement

Upward movement causes upliftment of continental masses in two ways

  1. The upliftment of whole continent or part there of
  2. The upliftment of Coastal land of the continents and such type of upliftment is called EMERGENCE

Downward Movement

Downward movement causes subsidence of continent in two ways

  1. The subsidence of the land area
  2. Alternatively, the land area near the sea coast is moved downwards or subsided below sea level and is thus submerged under seawater and such type of downward movement is called SUBMERGENCE

OROGENETIC MOVEMENTS

Orogenetic movements results in the formation of mountains which are caused due to the Endogenetic forces working in a horizontal manner. The horizontal forces and the resultant movements are also called as ‘tangential forces’. These forces work in two ways and they are

Tensional Force

These forces operate in opposite direction and thus create ruptures, cracks, fractures and faults in the crustal parts of the earth. Such type of forces and movements are also Called as DIVERGENT forces and movements.

Compressional Force

These forces operate towards each other or face to face and they cause crustal bending leading to the formation of folds
or crustal warping leading to the local rise or subsidence of crustal Parts. They are also called as CONVERGENT forces.

Crustal Bending

When horizontal forces work face to face the crustal rocks are bent due to the resultant Compressional and tangential force, the crustal rocks undergo the process of ‘crustal bending’ in two ways

  1. Warping
  2. Folding

The process of crustal warping affects larger areas of the crust where in crustal parts are warped upward or downward. The upward rise of the crustal part due to the compressive force resulting in the Convergent horizontal movement is called UPWARPING while bending of the Crustal parts downward in the form of a basin or depression is called DOWNWARPING. When the process of upwarping and downwarping affects larger areas, the resultant mechanism is called BROADWARPING. When the compressive horizontal forces and the resulting convergent movements cause buckling and Squeezing of crustal rocks, the resultant mechanisms is called folding which causes several types of folds.

Folds

Wave like bends are formed in crustal rocks due to the tangential compressive force resulting from horizontal movement caused by the Endogenetic force originating deep within the earth. Such bends are Called ‘folds’ Where in Some parts are bent up and some parts are bent down.

Figure 3 Different Components of fold

The up folded rock strata in arch-like form are called ‘anticlines’ while the down folded feature forming trough-like feature is called ‘synclines’. The two sides of the fold are called limbs of the fold. The limb which is shared between an anticline and its companion syncline is called middle limb. The Planes which bisects the angle between the two limbs of the anticline or middle limb of like syncline is called the axis of fold or axial plane. On the basis of anticline and syncline these axial planes are called as axis of anticline and axis of syncline respectively.

Figure 4 Anticlines and Synclines

Dip

The inclination of the rock beds with respect to the horizontal Plane is termed as ‘dip’. Two information are derived from the dip

  1. The direction of maximum slope down a bedding Plane
  2. The angle between the maximum slope and the horizontal plane

The direction of the dip is measured by its true bearing in relation to east or west of north e.g. 60°NE; while the angle of dip is measured with an instrument called clinometer.

Strike

The Strike of an inclined bed is the direction of any horizontal line along the bedding plane. The direction of the dip is always at right angle to the strike.

Figure 5 Dip and Strike

Anticlines

The unfolded rock beds are called anticlines. In simple fold the rock strata of both the limbs dip in opposite directions. Sometimes, folding becomes so acute that the dip angle of the anticline is accentuated and the fold becomes almost vertical. When the slopes of both the (limbs or the sides) of the anticline are uniform, the anticline is called ‘symmetrical anticline’ but when the slopes are unequal, the anticline is called as ‘asymmetrical anticline’. Anticlines are divided in to two types on the basis of dip angle

  1. Gentle anticline when the dip angle is less than 40° , sometimes 1°or2°
  2. Steep anticline when the dip angle ranges between 40° and 90°
Synclines

The Down folded rock beds due to compressive forces caused by horizontal tangential forces are called synclines. These are trough like form in which beds on either side ‘incline together’ towards the middle part. If folded intensely, the synclines assume the form of a canoe.

Anticlinorium

Anticlinorium refers to those folded structures in the regions of folded mountains where there are series of minor anticlines and synclines with one extensive anticline. They are formed when the horizontal compressive tangential forces do not wok regularly. Such type of fold is also called as fan fold.

Figure 6 Illustration of Anticlinorium and synclinorium

Synclinorium

Synclinorium represents such folded structure which includes an extensive syncline having numerous minor anticlines and synclines which formed due to irregular folding of irregular compressive forces.

Types of folds

The Nature of the folds depends on various factors such as the nature of rocks, the nature and the intensity of compressive forces, duration of the operation of the compressive forces etc. Based on the inclinations of the limbs the folds are classified in to 5 types.

Figure 7 Types of folds

  1. Symmetrical folds
  2. Asymmetrical folds
  3. Monoclinal folds
  4. Isoclinal folds
  5. Recumbent folds
Symmetrical folds

If both the limbs incline uniformly then they are called as symmetrical folds. These folds are an example of open folds and are formed when Compressive forces work regularly but with moderate intensity.

Asymmetrical folds

These are characterized by unequal irregular limbs which incline at different angles. One limb is relatively larger and the inclination is moderate and regular while the other limb is relatively shorter with Steep inclination.

Monoclinal folds

These are the folds in which one limb inclines moderately with regular slope while the other limb inclines steeply at right angle and the slope is almost vertical.

Isoclinals folds

These folds are formed when the compressive forces are so strong that both the limbs of the fold become parallel but not horizontal.

Recumbent folds

These folds are formed when compressive forces are so strong that both the limbs of the folds become parallel as well as horizontal.

Overturned folds

The folds in which one limb of the fold is thrust upon the another fold due to intense compressive forces. Limbs are season horizontal.

Plunge folds

When the axis of the fold instead of being parallel to the horizontal plane becomes tilted and forms plunge angle which is the angle between the axis and the horizontal plane.

Fan folds

They represent an extensive broad fold consisting of several minor anticlines and synclines which resembles a fan. Such feature also called as Anticlinorium and synclinorium.

Open folds

The folds in which the angle between the two limbs of the fold is more than 90° but less than 180° (obtuse angle). These open folds are formed due to wave like folding because of moderate nature compressive forces.

Figure 8 Open Folds

Closed folds

The folds in which the angle between the limbs is acute then they are called as closed folds and are formed due to intense Compressive forces.

Figure 9 Closed Folds

Nappes

Nappes are the result of complex folding mechanism caused by intense horizontal movement and resultant compressive forces. Both the limbs of the recumbent fold are parallel and horizontal. Due to further increase in the continued compressive force one limb of the recumbent folds slides forward and overrides the Other fold This process is called ‘thrust‘ and the Plane along which one Part of the fold is thrust is called ‘thrust plane’. The upthrust part of the fold is called ‘Overthrust fold’. When the compressive forces become so acute that it crosses the limit of elasticity of the rock beds, the limbs of the fold are so acutely folded that these break at the axis of the fold and the lower rock beds come upward. Thus the resultant structure becomes reverse to the normal structure. Due to continued horizontal movement and compressive force the broken limb of the fold is thrown several kilometers away from the original structure and overrides the rock beds of the distant Place. Such type of structure becomes unconformal to the original structure of the place where the broken limb of the fold of other place overrides the rock beds. Such broken limb of the fold is called ‘napple‘.

Figure 10 Formation of Nappes

Several examples of nappes are traceable in the present folded mountains. The nappes of the Alps have been systematically studies and divided in to four major groups from below upward they are

  1. Helvetic nappe
  2. Pennine nappe
  3. Austride nappe
  4. Dinaride nappe

 

In most of the localities the overriding nappes have been eroded away because of dynamic wheels of denudation processes and thus buried basic structure has been exposed. When the Portion of lower nappe is seen because of the denudation of overriding nappe, the resultant open Structure is called ‘structural window’. Several examples of ‘complete window’ have been discovered in eastern Alps. A few examples of nappes have also been traced out in Himalayas. When the broken limb of a fold overrides the other fold near the broken fold, the resultant nappe is called ‘Autochthonous Nappe’. On the other hand, when the limb of a fold, after being broken, overrides the other fold at a distant place, the resultant nappe is called ‘exotic nappe’.

Crustal Fracture

Crustal fracture refers to displacement of rocks along a plane due to tensional and Compressional forces acting either horizontally or vertically or sometimes even in both ways. Crustal fracture depends on the strength of the rocks and intensity of tensional forces. The crustal rocks suffer only cracks when the tensional force is moderate but when the rocks are subjected to intense tensional force, the rock beds are subjected to dislocation and displacement resulting in to the formation of faults. Generally fractures are divided in to 2 types

  1. Joints
  2. Faults

Joints

A joint is defined as a fracture in the crustal rocks wherein no appreciable movement of rocks takes place.

Faults

When the crustal rocks are displaced, due to tensional movement caused by the Endogenetic forces, along a plane, the resultant structure is called fault. The Plane along which the rock blocks are displaced is called fault plane. A fault Plane may be vertical, 0r inclined, or horizontal, or curved or of any type and form. The movement responsible for the formation of a fault may operate in vertical or horizontal or in any direction.

Figure 11 Different Components of a Fault

Fault Plane

The plane along which the rock blocks are displaced by tensional and Compressional forces acting vertically and horizontally to form a fault, fault plane may be vertical, inclined, horizontal, curved or of any other form.

Fault dip

The angle between the fault plane and the horizontal plane

Upthrown side

Represents the uppermost block of a fault

Downthrown Side

Represents the lowermost block of a fault

Hanging Wall

The upper wall of the fault

Foot wall

The lower wall of the fault

Fault scrap

The steep wall like slope caused by faulting of the crustal rocks, Sometimes the fault scarp is so steep that is resembles a cliff. Scarps are not formed by faulting alone and it may form due to erosion also, but whenever these are formed by faulting they are called ‘fault scraps‘.

Types of Faults

The different types of faulting of the crustal rocks are determined by the direction of the motion along the fracture plane. Generally, the relative movement or displacement of the rock blocks occurs approximately in two directions

  1. To the direction of the dip-Dip slip movements
  2. To the direction of the strike-Strike slip movements

Thus on the basis of the direction of slip or displacement faults are divided into

  1. Dip-slip faults
  2. Strike –slip faults

Normal Faults

If the displacement of the rock blocks is down to the direction of the dip then the resultant fault is called Normal fault. Normal faults are formed due to the displacement of both the rock blocks in opposite directions due to tensional force. The fault plane is usually between 45° and vertical. The Steep scrap resulting from the normal fault is called fault-scarp or fault-line scarp the height of which ranges between a few metres to hundreds of metres.

Reverse Faults

Reverse faults are formed due to the movement of both the fractured rock blocks towards each other. The fault Plane, in a reverse fault is usually inclined of an angle between 40° and horizontal 0° .The vertical Stress is minimum while the horizontal stress is maximum. In reverse faults the rock beds on the upper side are displaced up the fault plane relatively to the rock beds below .It is apparent that reverse faults results in the shortening of the faulted area while normal faults cause extension of the faulted area. It is thus, also obvious that some sort of compression is also involved in the formation of reverse faults. Reverse faults are also called of thrust faults. Since reverse faults is formed due to compressive force resulting from horizontal movement and hence this is also called as Compressional fault. When the compressive force exceeds the strength of the rocks , one block of the fault overrides the other block and the resultant fault is called as Overthrust fault where in the fault plane becomes almost horizontal.

Figure 12 (A) Normal fault and (B) Reverse Fault

Lateral or Strike Strip Faults

This type of faults are formed When the rock beds are displaced horizontally along the fault plane due to horizontal movement These are called left-lateral or sinistral faults when the displacement of rocks occurs to the left on the far side of the fault and right lateral or dextral faults when the displacement of rock blocks takes place to the right on the far side of the fault.

Figure 13 Formation of Strike -slip or transcurrent faults

Step Faults

When a series of faults occur in any area in such a way that the slopes of all fault planes are in the same direction the resultant faults are called step faults. It is a prerequisite condition for the formation of step faults that the downward displacement of all the downthrown blocks must occur in the same direction.

Figure 14 Illustration of Step faults

Rift Valley and Graben

Rift valley is a major relief feature resulting from faulting activities. It represents a trough, depression or basin between two crustal Parts. Rift valleys are formed due to displacement of crustal Parts and subsidence of middle portion between two normal faults by horizontal and vertical movements motored by Endogenetic forces Rift valley are generally also called as ‘graben’ which is a German word which means trough-like depression. A rift valley may be formed in two ways viz

  • When the middle portion of the crust between two normal faults is dropped downward while the two blocks on the either side of the down dropped block remain stable
  • When the middle portion between two normal remains stable and the two side blocks on the either side of the middle position are raised upward

Figure 15 Illustration of rift valleys and graben

Rhine rift valley is the best example rift valley. The one side of the rift valley is bounded by Vosges and Hardt mountains (block mountains-horst) while the other side is bordered by Black forest and odenwald mountains. Some of the other rift valleys are Jordan River valley, Death Valley of southern Californian and Dead Sea in Asia. The rift valleys are not only confined to continental crustal surfaces but they are also found on the sea floor. The deepest grabens are found in the form of ‘ocean deeps’ and trenches.

Figure 16 Rhine Rift Valley

Figure 17 Rhine and Death Valley of California

Origin of rift valleys

The hypothesis regarding the origin of rift valleys are generally grouped in to two categories

  1. Tensional hypothesis-based on tensional forces
  2. Compressional hypothesis-based on compressional forces

Both these hypothesis have lot of limitations and was not able to solve many of the intricate problems of the origin of rift valley.

Hypothesis of E.C Bullard

E.C. Bullard, while conducting the gravity survey, postulated his new concept of the origin of the rift valleys and according to him the formation of rift valley is completed through a series of sequential phases of compressional forces coming from both the sides of the land. The horizontal compressive forces work face to face from both the sides of the land. This lateral compression becomes so enormous that it exceeds the strength of the rocks; a crack is developed at a place in the crustal rocks. This crack is gradually enlarged due to continuous increase in the compressive force.

Figure 18 Stage 1

Second stage, due to the formation of crack, one portion overrides the other Portion and this portion is called thrusting. On the other hand, the second part is thrown downward relative to the first part. This process is called down thrusting.

Figure 19 Second Stage

A-C part has gone upward because of over thrusting .Due to the Upthrusting of the side block (A-C) up to a height of few thousand metres the downthrust block(A-D) develops crack at a place (B) due to the resultant compressive force. The place of the crack is located at the highest point of the downthrust block. This newly formed crack continues to increase gradually.

Figure 20 Third Stage

Third stage,the crack developed at downthrust block B place becomes enlarged due to increased compression with the result B-D part of the downthrust block overrides its other part (A-B).Thus, the position of downthrust A-B part between the two upthrust blocks (A-C and B-D) becomes rift valley.

EXOGENETIC FORCES

The exogenetic forces or Processes, also called as denudational processes, or ‘destructional forces or processes’ are originated from the atmosphere. These forces are continuously engaged in the destruction of the relief features created by Endogenetic forces through their weathering, erosional, depositional activities. Denudation includes both weathering and erosion where weathering being a static process includes the disintegration and decomposition of rocks in situ whereas erosion is dynamic process which includes both, removal of materials and their transportation to different destinations.

WEATHERING

Weathering is basically of three types

  1. Physical or Mechanical weathering
  2. Chemical weathering
  3. Biological weathering

These processes are very important for the biosphere ecosystem because weathering of parent rocks results in the formation of soils which are very essential for the sustenance of the biotic lives in the biosphere.

EROSION

The erosional processes include running water or river, ground water, sea –waves, glaciers, periglacial processes and wind. These erosional processes erode the rocks, transport the eroded materials and deposit them in suitable places and thus form several types of erosional and depositional landforms of different magnitudes and dimensions.

 

Advertisements

The Public Interest

Public administration is vitally concerned with efficiency and economy. Alongside this efficiency approach there has been a growing concern about what may broadly be called ‘morality’ or ‘ethics’ in Public administration. Government has to serve the common good without making any sort of distinction between men. Efficiency in government has thus a moral tone. Against this background the broad theory of public interest has emerged to provide general frame work for the functioning of public administration. There are several reasons for the concern for public interest .The members of the bureaucracy constitutes of Power elite. They are likely to take decisions in self-interest or under pressure from the Powerful interest groups. In either case, Public interest suffers. Further, the bureaucracy is a mindless machine that turns out decisions mechanically .The rule- bound administration may look neat and tidy, but it may not be able to serve the wider cause of public interest. According to Herbert Simon, administrative decisions are often based on grounds other than those of efficiency and economy. Social and psychological factors greatly influence the way decisions are taken by the decision-makers .The importance of a Sense of public interest as wider ethical Commitment in public administration assumes significance in this context.

Philosophies of Public administration fall broadly in to four classes:

  1. Intuitionism
  2. Perfectionism
  3. Utilitarianism
  4. Theory of Justice

Intuitionism

The administrator Choose an alternative by intuition-a solution which seems to him the right Course of action under the given Circumstance.

Perfectionism

The administrator views Public interest from the standpoint of promotion of excellence in all spheres of Social activities. Public resource should be spent in such a way that the best members of the Society benefit most from the expenditure. Thus seen Perfectionism is an elitist Philosophy and anti-egalitarian and is not compatible with democratic society.

Utilitarianism

According to Utilitarian Philosophy the Public interest is served When a Public policy makes as many as possible better-off even though it may render a few worse-off. Public interest is judged by the augmentation of the net balance of social satisfaction.

Theory of Justice

This theory has two principles .The first principle is that each person is to have an equal right to the most extensive basic liberty compatible with a similar liberty for others. The other principle postulates that Public Policies are reasonably expected to be to everyone’s advantage and public position and offices are open to all. In case of Conflict between these Principles, the second Principle is expected to prevail and give way to the first. These principles provide an operating logic for the determination of public interest by the decision- makers.

Philosophies of Public administration- A Review

Of all the major ethical frameworks for public administration, the intuitionist Philosophy justifies the Status quo and is of very little help in actual administrative situation .The Perfectionalist philosophy favours excellence at the expense of social equality. It is antidemocratic. Utilitarian Calculus has the merit of emphasizing total social good, but it also accepts the Position that a few may be worse-off. Compared to all these Philosophical positions, the theory of justice seems much more balanced and represents a workable way for determining the public interest by public administrators.

Human factor in Administration    

The human factor is the central Concern of public administration .It is meant for human beings and is manned by people. Firstly, it is involved in the relations between administration and its employers and Secondly, between administration and the administered, the public. In the recent pass, the State has been assuming new and newer responsibilities and has been entering in to hitherto forbidden fields. A large organization functions through standardized systems and methods .In this process, the human aspect is likely to be ignored. The human factor is exposed to risk of being forgotten or neglected .It is essential to maintain effective communications and relationships with employees within the general framework of organization, Command and discipline requirements. The Second aspect relates to the Relationships between the administration and the administered. The meaning of the word ‘administration’ as derived from the Latin root word; suggest that the administrator should regard himself as a servant, not the master. The people, not the administrators, are the centre of things and they should always be approach on terms of friendly equality. According to Jawaharlal Nehru “Administration like most things is, in the final analysis, a human problem to deal with human beings, not with some Statistical data ….. …The administrator may think in abstract of people he deals with, but which miss the human element. After all, whatever department you deal with, it is ultimately a problem of human beings. Administration is meant to achieve something and not to exist in some Kind ivory tower; following certain rules of Procedure and Narcissus-like looking on itself with complete self satisfaction .The test after all is humor beings and their welfare.

Public Administration-a Synoptic view

Public administration, as commonly defined, is the activity of the state in the exercise of its Political powers; in a narrow sense, the activity of the executive departments in the conduct of the government. In a literal sense of the term, Public administration also includes the functions of the courts in the administration of justice and the work of all the agencies, military as well as Civilian, in the executive branch of the government. A broader definition would include consideration of judicial structure and procedure and likewise the special machinery and methods employed by the armed forces in addition to legislative management. But in practice the scope of the activities of public administration is restricted to the organization and operations of the executive branch of the government only. It is felt that if all the Complex activities of all three branches of government, which are undertaken to fulfill public purposes, are studied, the subject will become unwieldy leading to confusion and losing its unity. Thus in the narrow sense, public administration includes primarily the organization, personal practices and Procedures essential to the effective performance of civilian functions entrusted to the executive branch of government. Public administration is primarily concerned with the implementation of public Policy laid down by representative Political bodies. Its main task is essentially the implementation and enforcement of public policy and the law of the state. It is both a process and vocation, with the management of the activities of others in the public agency. The activities of public administration are expressed through organization and human beings. Public administration is a human activity. It is managed by the human beings and it serves human beings .It is the action part of the government, the means by which the purposes and goals of government are realized. The Scope of public administration is to Study the Problems of men, materials and methods in administration. Keeping in view the activities of the present day administration the Study of public administration should include

  1. Administration as a process common to government at all level-central, State and local
  2. The activities of the government and the methods used by operating officers
  3. Personal and financial management
  4. Public relations and public accountability
  5. Social and cultural environment
  6. Human behavior of those in the heart of administrative activities
  7. Human beings who use the tools and techniques of administration

Felix A. Nigro has summarized the various aspects of the definition and scope of public administration as follows:

  1. It is a cooperative group effort in public setting.
  2. Covers all three branches-executive, legislative, and judiciary and this interrelationships
  3. It has an important role in the formulation of public policy and is thus a part of political process
  4. It is more important than, and also different in significant ways from private administration
  5. As a field of Study and practice, it has been much influenced in recent years by human-relation approach
  6. It is closely associated with numerous private groups and individuals in providing services to the community.

Rocks

Introduction

    The Materials of crust or lithosphere is Called rocks. The smallest components of the earth’s crust is Called elements. As regards to earth the eight most abundant elements of earth are (iron, oxygen, silicon, Magnesium, nickel, sulphur, Calcium and ammonium) constitute 99% of the total mass of the earth whereas only four elements (iron, oxygen, Silicon and magnesium) account for 90% of the total mass of the earth. On the other hand, the eight most abundant elements which constitute 99% of total mass of the Crust are oxygen, silicon, aluminum, iron, magnesium, Calcium, Potassium, and Sodium.
 

Table 1 Whole Earth
 

Elements 

Percentage 

Iron 

35 

Oxygen 

30 

Silicon 

15 

Magnesium 

13 

Nickel 

2.4 

Sulphur 

1.9 

Calcium 

1.1 

Aluminium 

1.1 

Others,less than 

1.0 

  

Table 2 Earth’s Crust
 

Elements 

Percentage 

Oxygen 

46 

Silicon 

28 

Aluminium 

8 

Iron 

6 

Magnesium 

4 

Calcium 

2.4 

Potassium 

2.3 

Sodium 

2.1 

Others, lessthan 

1.0 

More than one elements of the earth’s crust are organized to form Compounds which are known as minerals and minerals are organized to form rocks. The important mineral groups are silicates, Carbonates, Sulphides, metal oxide etc.
 

The Silicate Minerals

    These are very important rock making minerals. The most outstanding rock forming silicate mineral groups are quartz, feldspar and ferromagnesium.Quartz is composed of two elements viz. silicon and oxygen and is generally a hard and resistant mineral .The most abundant and the most important rock forming silicate mineral is feldspar which is also very important economically because it is used in ceramics and glass industry. Feldspar is very weak mineral and is easily broken down due to Chemical weathering and is changed into Clays as hydrated alumino silicates. When silicon and oxygen combine with iron and magnesium, ferromagnesium minerals formed. Ferromagnesium minerals are easily weathered and are eroded away .The rocks having abundant ferromagnisium minerals Provide weak structure for the Construction of of building roads, dams, reservoirs etc. 

Carbonate Group of Minerals

    This group of minerals is very much susceptible to chemical weathering and erosion in humid areas. Calcite is the most important mineral of this group. Limestones and marbles having abundant Calcite are corroded by the surface and the groundwater and extensive Caves are formed below the ground surface. Such areas provide very weak structures for construction sites. 

Sulphide Minerals

    Includes Pyrites, iron Sulphides etc. when these minerals come in Contact with water or air, these form ferric hydroxides and sulfuric Acids which causes serious environmental problems. 

Metallic elements

    Iron, Aluminium etc. after reacting with atmospheric oxygen form metal oxides which are commercially Very important. 

Rocks, thus, representing the geomaterials of the earth’s crust, are composed of two or more minerals. 

 

Classification of Rocks

 

Rock Cycle

 

 

‘The landscape is a function of structure, process and time (stages)’-W.M.Davis 

Igneous Rocks

Introduction

    The word igneous has been derived from the word `ignis’, meaning there by fire. The igneous rocks are formed due to the cooling, solidification and crystallization of hot and molten materials known as magmas and the lavas and thus these rocks are called as Primary Rocks, since they originated from liquid magmas which were present when the earth was formed. The igneous rocks also called as Parent rocks, since all the Subsequent rocks were formed their directly or indirectly from them. It is believed that the igneous rocks were formed during each period of geological history of the earth and are still being formed.

Characteristics of Igneous Rocks

  • Generally, igneous rocks are roughly hard and water percolates with great difficulty along the joints. Some times the rocks become so soft, due to their exposure to environmental Conditions for longer duration (e.g. basalt).
  • Igneous rocks are granular or crystalline but these are much variations in the size, form and texture of grains because these Properties largely depend upon the rate and Place of cooling and Solidification of magmas or lavas. When the lavas are quickly Cooled down and solidified, there is no sufficient time for the crystals to develop and this results in small quantities of crystals if not complete absence of it (e.g. basaltic rocks) and in contrary to this if the magmas are cooled and Solidified at a very Slow rate inside the earth then these is sufficient time for the full development of grains and thus the resultants rocks are coarse-grained.
  • Unlike the sedimentary rocks the igneous rocks does not contain Strata but do have the Presence Of Several layers of lava because lava flows in a region occur in several Phases, layers after layers of lava are deposited and solidified and often these is a Confusion about the layers or Strata but in reality there are no Strata.
  • Since igneous rocks are impregnable they are not affected by Chemical weathering but basalts are very easily weathered and eroded away when they come in constant touch with water. Coarse grained igneous rocks are affected by mechanical or Physical weathering and thus the rocks are easily disintegrated and decomposed.
  • Igneous rocks are void of fossils because igneous rocks Solidified from molten magma when there was no life on the newly born earth and since they are formed from very hot molten materials, the remains of Plants and animals may be destroyed of very high temperature prevalent in magmas.
  • Igneous rocks contain numerous joints since they were formed due Cooling and contraction of magmas.
  • Igneous rocks are mostly found in volcanic zones and are associated with volcanic activity; hence they are also called as volcanic or magmatic rocks.

Classification of igneous rocks

    There are vast variations found in the characteristics of igneous rocks and hence they are classified on several grounds as follows

The most traditional method of Classification of igneous rocks is based on the amount of silica (Sio2) in this way they are classified into two broad categories,

  1. Acidic Igneous rocks- having more silica
    e.g. granites
  2. Basic Igneous rocks-having lower amount of silica e.g. gabbro

On the basis of chemistry and mineralogical composition the igneous rocks are classified in to two dominant groups (light and dark minerals)

  1. Felsic Igneous rocks- composed of dominant minerals of light groups such as quartz and feldspar having rich content of silica.
  2. Mafic igneous rocks- Composed of dominant mineral of dark group Such as pyroxenes, amphiboles and Olivines, all of which have rich contents of magnesium and iron.
  3. Ultramafic igneous rocks- are characterized by the abundance of pyroxenes and olivine minerals, examples, periodite, dunite.

The igneous rocks are more commonly classified on the basis of the Mode of occurrence into two major groups.

  • Intrusive Igneous rocks
  1. Plutonic igneous rocks
  2. Hypabassal igneous rocks
  • Extrusive igneous rocks
  1. Explosive type
  2. Quiet type

Intrusive igneous rocks

When the magmas are cooled and solidified inside the earth then the resultant igneous rocks is called as intrusive igneous rocks.

Plutonic igneous rocks

    If the cooling of the magmas occurs very deep inside the earth then they are called Plutonic igneous rocks. Since the rate of cooling is extremely slow there is sufficient time for the development of large crystals. Example, granite

Hypabassal igneous rocks

    If the Cooling and solidification of magmas occur just beneath the earth surface along Pores, holes and hollow spaces, then the resultant rock is called as Hypabassal rocks. The magmas are solidified in to different forms depending on the Places in which they are solidified such as Batholiths, loccoliths, phacoliths, lopolilths, Sills etc.

Batholiths

    Batholiths are long, irregular and undulating forms of solidified magma usually of dome shaped with their side walls being very steep, almost vertical. The upper portion of the batholiths are Seen when the superincumbent cover is removed due to continued denudation but their bases are never seen because they are buried deep inside the earth. Exposed batholiths are subjected to weathering and erosion because of which they appear to be highly irregular or corrugated.



Laccoliths

    Laccoliths are of mushroom shape having convex summital form. The ascending gases during a volcanic eruption force the upper Strata of the flat layered sedimentary rocks to arch up in the form of convex arch or a dome .consequently, the gap between the arched up or domed upper Strata and horizontal lower Strata is injected with magma and other volcanic materials.

Phacoliths

    Phacoliths are formed due to the injection of magma along the anticlines and Synclines in the regions of folded mountains.

Lopolith

    When magma is injected solidified in a concave Shallow basin whose central part is sagged downwards .The resultant form of solidified magma is Called lopolith. These are generally coarse grained because of slow process of cooling of magmas.

Sills

    Sills are formed due to the injection and solidification of magmas between the bedding Planes of sedimentary rocks. Thick beds of magma are called sills whereas thin beds are Called Sheets. Their thickness ranges from few centimeters to metres. When Sills are tilted together with sedimentary beds due to earth movements and are exposed to exogenous denudational process, they form significant landforms like cuesta, hogbacks and ridges.

Dykes

    Dykes represent wall-like formation of Solidified magmas. They are mostly perpendicular to the beds of sedimentary rocks. Their thickness ranges from centimeters to several hundred metres but length extends from a few metres to several kilometers. When these dykes are filled up with water then they are called Dyke Lake.

    
 

    

Extrusive Igneous rocks

    When igneous rocks are cooled and solidified at the earth’s surface then they are Called extrusive igneous rocks. Generally, extrusive igneous rock is formed during fissure eruption of volcanoes resulting into flood basalts. These rocks are also called as volcanic rocks. Generally these rocks are fine grained or glassy basalts because lavas after Coming over earth’s surface are quickly cooled and solidified due to Comparatively low temperature of the atmosphere and thus these is no enough time for the development of grains or crystals. Some examples of extrusive igneous rocks are Basalt, Gabbro, and obsidian. Extrusive igneous rocks are further subdivided into two types, explosive type, and quiet type.

Explosive type

    The igneous rocks formed due to the mixture of volcanic materials ejected during explosive type of violent volcanic eruptions are called explosive type of extrusive igneous rocks. Volcanic materials include ‘bombs’ –big fragments, ‘lapilli’– small fragments, volcanic ashes and dusts. ‘Tuffs’ are fine volcanic materials deposited in aquatic conditions. The mixtures of larger and smaller grains are called ‘breccia’ or ‘agglomerates’ which are badly consolidated and susceptible to erosion.

Quiet type

    The appearance of lavas through minor cracks and openings of the earth surface is called ‘lava flow’ .These lavas after Cooling and solidification form basaltic igneous rocks of quiet type. Flood basalts resulting from several episodes of lava flow during fissure flows of volcanic eruptions form extensive ‘lava plateau’ and ‘lava plains’ Where in Several layers of Basalt are deposited one upon another.

Classification of Igneous rocks on the basis of Chemical Composition

Acid igneous rocks

    These rocks contain silica content between 65-85% and their average density varies from 2.75-2.8. Quartz and white and pink feldspar are the dominant minerals. Granite is the most significant example of this group of rocks. Generally these rocks lack in iron and magnesium, they are hard and relatively resistant to erosion. These rocks which are light in weight are used as building materials because of their less erosive.

Basic igneous rocks

    These rocks contain silica content between 45 to 60 %. Their average density ranges from 2.8 to 3.0. These are dominated by Ferro magnesium minerals. There is very low amount of feldspar. The rock is heavy in weight and dark in colour because of the dominance iron content. They are easily eroded away when they come in regular contact with Water. The fine grained Basalt, gabbro, dolerite are examples of this group.

Intermediate igneous rocks

    These rocks are those in which the silica content is less than the amount present in acid igneous rocks and more than the content of Basic igneous rocks. Their average density is between 2.75 and 2.8. Diorite and andesite are representative examples of this group of rocks.

Ultra basic igneous rocks

    Carries silica content less than 45% but their average density is 2.8 to 3.4 %. Periodotite is a typical example of this group of rocks.

On the Basis of the Texture of Grains

  1. On the basis of the size of the grains igneous rocks are generally divided in to
  2. Coarse grained igneous rocks –Plutonic igneous rocks comes under this Category, ex: Granite
  3. Fine grained igneous rocks-extrusive igneous rocks falls under this category; ex-Basalt.

Medium-grained igneous rocks- Hypabassal rocks are generally medium grained igneous rocks.

The igneous rocks are classified On the basis of texture of grains in to six subtypes

  1. Pegmatitic igneous rocksvery coarse grained igneous rocks including very large crystals of several metres across. Examples: Plutonic Igneous rocks like Pegmatitic granites,pegmatitic diorites,Pegmatitic synite etc
  2. Phaneritic igneous rockscoarse grained igneous rocks,Examples:Plutonic igneous rocks like Granites,diorties etc
  3. Aphanitic igneous rocksvery fine grained igneous rocks and invisible to naked eyes, Examples: Basalt, Felsiteand the rocks of sills and dykes.
  4. Glassy igneous rockswithout grains of any size,Examples:pitch stones,obsidians,pumice,perlite etc
  5. Porphyritic igneous rocksmix grained igneous rocks.
  6. Fragmental igneous rocks-consisting of bombs, lappili, breccia, volcanic dusts, ashes and tuffs etc.

Important igneous rocks

Granites

Granite is the most significant example of Plutonic intrusive igneous rocks which are formed deep within the earth. Since the rate of cooling and solidification of magmas inside the earth is very slow because of the very high temperature prevailing underground there is enough time for Granites to develop large sized grains. Granites are essentially composed of minerals of quartz, feldspar and mica with feldspar being the most abundant mineral, mainly orthoclase. Sometimes, the minerals are uniformly distributed and all of them are almost of same size. Besides, albite, biotite, muscovite and hornblende are also found in granite rocks.

                

Mineral Composition of Granite

  Feldspar Quartz Mica Hornblende Iron Others
Percentage 52.3 31.3 11.5 2.4 2.0 0.55

 

The granite rocks are differentiated on the basis of their texture and mineralogical composition, for example, Hornblende granite –When hornblende mineral is most dominant. From the Standpoint of Chemical composition granites are acidic rocks where in Silica content ranges between 65-85%. Granites are generally light in weight as their density varies from 2.75 to 2.8. There is also wide range of colour variation in different-types of granites, they are generally light in colour but if orthoclase mineral is present in abundance, the granites become pink to yellow or slightly reddish in colour. If dark coloured hornblende or biotite is a dominant mineral, the granites become of dark black or dark grey colour. Granites are generally resistant to erosion but when rocks are well joined, they are easily weathered and a very peculiar landform ‘tor’ is formed.

Basalts

Basalts are very fine-grained, dark-Coloured extrusive igneous rock which is formed due to Cooling and solidification of molten lavas at the surface of the earth. Sometimes the Cooling of lavas takes Place so rapidly that no time is available for the crystallization of basalt and hence no grains are formed, with the result the rock becomes glassy basalt. Basalts having grains though very minute are called aphanitic basalts. Chemically, basalts contain 45 to 65% of Silica content. Through the rock is heavy in weight it is susceptible to weathering and fluvial erosion .The dark-colour of basalt is because of the abundance of iron. Feldspar is the most dominant mineral, besides augite, olivine, mineral iron are present.
Sometimes, Polygonal cracks are developed in basalts due to contraction in Cooling of lavas. Columnar Jointing in basalts give birth to peculiar landforms Characterized by uneven terrain surfaces.

Mineral Composition of Basalt

    
 

            

Delegates from 192 countries including India landed in Copenhagen, Capital of Denmark on December 7, 2009 for two weeks of talks aimed at paving the way for new global treaty on Climate Change. Two Years ago at Bali, after a marathon negotiating session that left some delegates in tears, envoys from 192 nations set themselves a deadline of 2009. The task in question- to come up with the way of extending the essence of Kyoto Protocol (KP) beyond 2012 and mitigate climate change

Kyoto Protocol in brief

The Kyoto protocol (KP) was an agreement made under the United Nations Framework Convention on Climate Change (UNFCC). The treaty was negotiated in Kyoto, Japan in December 1997 and opened for signature on March 16, 1998 and closed on March 15th, 1999- After a Gap of one year .The KP entered in to force on 16th February 2005. As of October 2009, 184 States have signed and ratified the protocol. The most notable non-member of the KP is the United States, which is a signatory of UNFCCC and is responsible for 36% of the 1990 emission levels. According to Kyoto protocol the signatory countries have to reduce their Green House GAS (GHG) emissions by 5% below their 1990 levels. These talks are technically known as the 15th Conference of the Parties to the UNFCCC- often abbreviated to COP15.

History of Global warming and Climate change

Green House Gas (GHG) and the resulting Global Warming (GW) was discovered by Joseph Fourier in 1824, but was studied in depth by Swedish Scientist Svante Arrhenius in 1896. However, Scientists rejected Arrhenius’s assertion because they believed that CO2
did not absorb any part of radiation that was also not absorbed by Water vapour. The level of CO2 in the atmosphere was so small (0.033%) compared to the level of water vapour (1 to 5%) depending on temperature, that it only duplicated the effect of water vapour and its effect was insignificant on the Earth’s temperature. However in the 1930’s the British researcher, Guy Callender first compiled temperature Statistics for different regions and concluded that temperature had increased between the 1885-1950 intervals by about 0.5°C. Callender also concluded that the rise had to be due to the level of rising CO2 .A Johns Hopkins University researcher, Dr. Gilbert N. Plass, made calculations to show that increased levels of CO2 Could raise atmospheric temperature. It was this research that convinced Climatologists that carbon dioxide could affect Climate. During the last 100,000 years CO2 Content varied between a low Of approximately 200 parts Per million (PPM) during cold periods and a high of 280 PPM during the warm periods As of march 2009, Carbondioxide in the earth’s atmosphere is at a Concentration of 387 ppm.It was 387.35 PPM in December 2009 and is going up Slowly but surely. According to NASA Climatologist Dr-James Hansen, anything above 350 PPM is dangerous and leads to impacts such as melting of arctic sea ice that are happening much faster than the anticipation of scientists. The global average temperature has already gone up by about 0.7°C since Pre industrial times and in some Parts of the world this is already having severe impacts.

What did Copenhagen Summit Achieve?

The G8 and a number of developing countries have agreed that the average temperature rise should be limited to 2°c. In Principle, the delegates were looking to the Copenhagen treaty to curb the growth in greenhouse gas emissions Just enough to keep the temperature rise below the limit .The European union (E.U) has settled on targets of keeping GW from exceeding a 2° C rise in average temperatures, which roughly equates to CO2 Concentrations in the atmosphere of 450 ppm.It. After days of walk-outs, adjournments and protests, the Copenhagen accord was put forwarded on December 18th by the U.S.A, China, India and South Africa, among other countries. The Accord and its drafting brought into existence an entity, consisting of the large economics, labeled BASIC (Brazil, South Africa, India, and China). BASIC has not only to ensure universal acceptance of the Copenhagen Accord but also to carry forward the momentum that has been created for reaching a full fledged binding agreement in Mexico in 2010, in Coordination with the U.S.A. However the U.S.A and other developed countries are not ready for deep cuts in emissions because USA has 5% of the world’s population and 30% of the world’s Automobiles, but the country contributes 45% of the gases that causes Global warming and deep cut would hurt their economy badly and finally because of this deadlock the Copenhagen failed to achieve any meaningful breakthrough and as most People expected” The business will go on as usual”.

Copenhagen Climate Accord at a Glance

The following are the broad contours of the accord reached by the United States , China, India, Brazil, South Africa and several other countries at the UN Climate talks in Copenhagen-along with Current elements in place earlier:

Emissions

The deal does not commit any nation to emission cuts beyond a general acknowledgement that global temperatures should be held along the lines agreed to by leading nations in July. These are no overall emission targets for rich countries. The already agreed-upon emission Cuts fall far short of action needed to avoid potentially dangerous effects of climate Change. These cuts are to be made by 2020:

  • USA, a 17% reduction from 2005 levels (or 3-4 % from 1990 levels)
  • China, a cut of 40 to 45 % below “business as usual” that is judged against 2005 figures for energy used versus economic output
  • India, 20 to 25 % cut from 2005 levels.
  • European Union, 20% cut from 1990, and possibly 30%.
  • Japan, 25 % cut from 1990.

Verification

  • Countries are to list actions taken to cut global warming Pollution by specific amount.
  • Method is agreed upon for verifying reduction.
  • Developed nations already covered by the 1997 Kyoto Protocol (the USA is not included) will have their emission cuts monitored and will face possible sanctions if they fail to meet them.

Funding

  • Wealthy nations will raise $100 billion a year by 2020 to help poorer nations cope with the effects of climate change, such of droughts and floods. This is continents on a broader agreement, including some kind of oversight to verify China’s emissions of greenhouse gases.
  • Short term funding of roughly $30 billion over three years beginning in 2010 to help developing countries adapt to climate change and shift to clean energy

Introduction –The Public Interest

    Public administration is vitally concerned with the efficiency and economy. By spending least resources, the administration becomes result-oriented and Productive. Alongside this efficiency approach, there has been growing Concern about what may broadly be Called ‘morality’ or ‘ethics in Public administration. Government has to serve the common good without making any distinction between Man and man. Efficiency in government thus has a moral tone. Against this background the broad theory of public interest has emerged to provide general framework for the functioning of public administration. There are several reasons for the Concern of for public interest. The members of the bureaucracy constitute Power elite. They are likely to take decision in self interest or under pressure from powerful interest groups. Further, the bureaucracy is a mindless machine that turns out decisions mechanically. The rule-bound administration may look very neat and tidy, but it may not be able serve the wide Cause of public interest and according to Herbert Simon administrative decisions are often based on the grounds other than those of efficiency and economy. Social and psychological factors greatly influence the way the decision see taken by the decision-makers. Thus the importance of a sense of public interest as a wider ethical Commitment in Public administration assumes significance in this context.

Philosophies of Public interest fall broadly in to Classes.

  • Intuitionism:

    • The administrator Chooses on alternative by intuition- a Solution which seems to him the right course of action under the given circumstances.
  • Perfectionism

    • The view of the administrator here is that Public interest should be the Standpoint of promotion of excellence in all spheres of social activities. Public resources should be spent in such a way that the best members of the society benefit most from the expenditure. Thus perfectionism is an elitist Policy and is not compatible with democratic society.
  • Utilitarianism

  • Theory of Justice

    • This theory has two principles. The first principle is that each Person is to have an equal right to the most extensive basic liberty compatible with similar liberty for others. The other principle postulates that public Policies public policies are reasonably expected to be everyone’s advantage and public positions and offices are open to all. In case of conflict between these principles, the second Principle is expected to Prevail and give way to the first. These Principles provide an operating logic for the determination of public interest by the decision makers.

These are the major ethical frameworks of the public administration. The intuitionist Philosophy Justifies status quo and is of very little help in an administrative situation .The perfectionist philosophy favours excellence at the expense of social equality. It is antidemocratic. Utilitarian calculus has the merit of emphasizing total Social good, but it also accepts the position that a few may be worse off. Compared to all these philosophical positions, the theory of justice seems much more balanced and represents a Workable way for determining the Public interest by the public administrators.

Human factor in public administration

    The human factor is the central concern of public administration. Firstly it involves the relationship between the administration and its employers and secondly between administration and the administered, the public. A large organization functions through standardized systems and methods. In this process, the human aspect is likely to be ignored and thus the human factor is exposed to the risk of being forgotten or neglected. It is always essential to maintain effective communications and relationships with the employees within the general framework of organization, Command and discipline requirements. The second aspect relates to the relationships between the administration and the administered. It is imperative that the administrator should regard himself as the servant and not as the master. The People, not the administrators, are the centre of the things, and they should always be approached on terms of friendly equality. The real motto of the administration should be the welfare of human beings.

Public Administration a synoptic view

    Public administration is primarily concerned with the implementation of the Public policy laid down by representative Political bodies. Its main task is essentially the implementation and enforcement of public policy and the law of the State. It is both a process and vocation. As a process it is concerned with the implementation of Policy and as a vocation, with the management of the activity of others in the Public agency. Public administration is a human activity. It is managed by the human beings and it serves human beings. It is the action Part of the government, the means by which the purposes and goals of the government are realized .The Scope of the public administration is to Study the problems of men, materials and the method of administration. Keeping in view the activities of the present day administration, the Study of public administration should include

  1. Administration as a process Common to governments at all levels-central, State and local.
  2. The activities of the government and the methods used by the operating officers.
  3. Personal and financial management.
  4. Public relations and public accountability.
  5. Social and cultural environment.
  6. Human behavior of those in the heart of the administrative activities.
  7. Human beings who use the tools and techniques of administration.

Summary of various aspects of the definition and Scope of Public administration

  1. It is a Cooperative group effort in the public Setting.
  2. Covers all three branches-executive, legislative and judiciary and their interrelationships.
  3. It has an important role in the formulation of Public Policy and is thus a Part of political process.
  4. It is more important than, and also different in significant ways from private administration.
  5. As a field of Study and practice, it has been much influenced in recent years by human-relation approach.
  6. It is closely associated with numerous private groups and individuals in providing services to the Community.

Sedimentary Rocks

Sedimentary rocks are formed due to the aggradations and compaction of the sediments. The word sedimentary has been derived from the Latin word which means settling down. The sedimentary rocks are also Called as Stratified or layered rocks and hence Consists of different types of layers and strata of various sediments. Some sedimentary rocks do not consist of layers, ex: loess.

Characteristics of Sedimentary rocks

  • Sedimentary rocks are formed of sediments derived from older rocks, Plants and animal remains thus these rocks contains fossils of animals and plants.
  • The sedimentary rocks are widespread about 75 % of the globe consists of sedimentary rocks and the remaining 25% by igneous and metamorphic rocks. Nevertheless the sedimentary constitute only 5 % of the composition of earth’s crust.
  • The deposition of sediments takes place in a certain sequence. The size of the Sediments decreases from the littoral margins to the centre of the water bodies.
  • The sedimentary rocks are consolidated and compacted by cementing elements Such as Silica, iron compounds, Calcite, Clay Etc
  • The consolidation of layers of sedimentary rocks depends upon the nature of cementing materials and the rocks are Seldom found in their original manner because of the lateral compressive and tensile forces
  • Sedimentary rocks are seldom crystalline but are Characterized by Joints perpendicular to the bedding Planes.
  • The connecting Plane between two consecutive beds or layers is called as bedding Plane.

Types of formation in Sedimentary rocks

    When two beds are uniform along the bedding Plane then this type of formation is called conformity.

    When two beds are not uniform then the structure is called as Unconformity.

Types of Unconformity

  • Non-conformity (where sedimentary rocks succeed igneous & metamorphic rocks)
  • Angular unconformity (where horizontal sedimentary beds are deposited over the previously folded strata)
  • Disconformity (where two conformable beds are separated by Changes in sediment type.
  • Paraconfirmity ( where two sets of conformable beds are Separated by same set of sediments)

  • Sedimentation units in the rocks which are more than One centimeter is called BEDS
  • The upper and lower surface of the beds are called BEDDING PLANE or BOUNDING PLANES

Sometimes the lower surface of the bed is called SOLE. There are further sedimentary units within a bed. The units having more than one centimeter is called layer or Strata Where as the units below one centimeter are Called laminae. Thus several strata and laminae make up a bed. When beds are deposited at an angle to the depositional surface they are called cross beds and the general phenomena of inclined layers are called cross lamination or cross bedding.

    Soft mud or alluvial deposits by rivers develop cracks when baked in sun and these cracks are generally of Polygonal Shape, such cracks are Called MUD CRACKS OR SUN CRACKS.

    Most of the sedimentary rocks are Permeable and Porous but few of them are nonporous and Impermeable

Classification of sedimentary rocks

  • ON THE BASIS OF NATURE OF SEDIMENTS
    • Mechanically formed or clastic rocks
      • Sandstones
      • Conglomerates
      • Clay rock
      • Shale
      • Loess
    • Chemically formed sedimentary rocks
      • Gypsum
      • Salt rock
    • Organically formed sedimentary rocks
      • Limestone
      • Dolomites
      • Coals
      • Peats
  • ON THE BASIS OF TRANSPORTING AGENTS
    • Argillaceous or aqueous rocks
      • Marine rocks
      • Lacustrine rocks
      • Riverine rocks
    • Aeolian sedimentary rocks
      • Loess
    • Glacial sedimentary rocks
      • Till
      • Moraines

Mechanically formed sedimentary Rocks

    Previously formed rocks are subjected to mechanical or physical disintegration these are called fragmental rock materials or Clastic materials which become the source materials for the formation of mechanical or clastic sedimentary rocks. These materials are further broken down in to fragments during their transportation by the exogenous process such as wind, running water glacier etc, some of the important members of this group are Sandstones, conglomerates, Silt, shale, Clay etc.

    Sandstones

        Sandstones are formed mostly due to the deposition, Cementation, compaction of Sand grains. The Sand grains are divided into five categories on the basis of their size

Classification of sands by grain size

Sand types Grain size (in mm)
  1. Very Coarse sand
1.0 to2.0
  1. Coarse Sand
0.5 to 1.0
  1. Medium sand
0.25 to 0.5
  1. Fine sand
0.125 to 0.25
  1. Very Fine sand
0.0625 to 0.125

                

 

These grains are deposited in the water bodies, and are aggravated and consolidated by Cementing elements such as Silica, Calcium, iron oxide Clay etc. The Colour of the sandstone Varies according to the nature of the cementing elements. Sandstones become red and gray when cemented by iron oxide and in to white when the cementing element is replaced by calcium Carbonate. They become hard and resistant when cemented by Silica. On an average the sandstones are generally porous rocks.

Sandstones

  • On the basis of mineralogical and textural Characteristics sandstones are classified in to the following types
  • Quartz Arenites (composed entirely of quartz grains)
  • Arkose Sandstones (feldspar being the dominant Mineral)
  • Lithic Arenites (composed of fine grained rock fragments derived from Shales, schist, slates and volcanic rocks).
  • Greywackle Sandstones (Composed of feldspar, rock fragments, quartz).

Note: The English word Arsenite is derived from Latin word Arena-meaning thereby Sand.

Conglomerates

        They are formed due to the consolidation and cementing of pebbles of various Sizes with Sands. Polished round fragments of size with 4 mm of diameter are called Pebbles and those with a diameter 256mm are called boulders. Angular rock fragments are Called breccia.

Clay rock and shale

        They are formed due to the deposition and cementation of fine sediments. Sediment having grain size of 0.3mm to O.4mm are called silts where as Clays are formed When the grain size is between 0.4mm to O. 00012 mm are Cemented or consolidated. Silt and Clay are soft weak rocks but are defiantly impervious. Clay rocks are formed exclusive Kaolin minerals and pure White in colour but they Change to different colours because of being mixed with impurities.

    Chemically formed sedimentary Rocks

        When Running Water containing chemicals come in touch with the rocks containing Soluble materials are washed away and come in contact with the Chemicals. The Chemical materials are then settled down, compacted and cemented to form Chemical sedimentary rocks such as gypsum and salt rocks.

    Organically formed sedimentary rocks

        The sediments derived from the disintegration and decomposition of Plants and animals deposit and consolidate to form organic sedimentary rocks. The rocks are divided in to three categories on the basis of its carbon and lime content. They are

Calcareous rocks

Carbonaceous rocks

Siliceous rocks

Calcareous rocks

    Calcareous rocks are formed due to the deposition and consolidation of sediments derived from the remnants of animals and plants which contain lime. Limestone is one of the examples of the calcareous rocks. Limestone is formed in the following Manner

                    Calcium oxide (Cao) reacts with water to form Calcium hydroxide Ca (0H) 2. This is given by the following equation,

                            

                    Then Calcium hydroxide reacts with Carbon dioxide (CO2) to give Calcium carbonate CaCo3 this is given by the following equation,

                            

    The calcareous rocks are collectively called as carbonate rocks or carbonates. Calcium carbonate (Caco3), Magnesium carbonate (Mgco3), dolomite (CaMg (co3)2 are important calcareous rocks. Limestone is both thinly beaded and thickly bedded. The most dominant minerals are calcite (Hexagonal), Aragonite (orthorhombic). Though Limestone are weak rocks in humid regions they become more resistant when exposed to dry climate, because of its uniform or homogenous structure they are not easily affected by differential expansion and contraction due to temperature. The Carbonate rocks after Chemical weathering give birth too karst topography. Chalks another form of Carbonate rocks are formed due to the Precipitation of Carbonate minerals desired from microorganisms like foraminifera.

 

                                                

ARGONITE ROCKS (ORTHOTHROMBIC) CALCITE ROCKS (HEXAGONAL)                                

Carbonaceous rocks

    These rocks contain Carbonic minerals which are mainly remains of vegetation. These rocks are formed when these remains are buried in the ground and undergo Changes because of pressure from overlying deposits and earth movements. The Initial form of carbonaceous rock is Peat which is dark grey in colour, and then subsequently it transforms into rocks with greater Proportion of carbon like lignite, bituminous, anthracite Coals. The coal layers one called coal seams. They are more important economically than geomorphically.

Siliceous rocks

    They are formed due to the dominance of silica Content. These rocks are formed due to the aggradations and compaction of sediments derived from radiolarian organisms (marine organisms that absorb silicon compounds during their lifecycle), sponge, diatom plants. Geyserites are also deposits of Silica around geysers.

ON THE BASIS OF TRANSPORTING AGENTS

    Based on major transporting agents the sedimentary rocks are classified in to three types

  • Argillaceous
  • Aeolian
  • Glacial

Argillaceous rocks

    These are also known as aqueous rocks because they formed in the water areas and are also transported by waters. They are called argillaceous rocks because of the presence of Clay and these rocks are characteristically soft. They are generally impervious rocks and are further sub-divided in to three types

  • Marine argillaceous sedimentary rocks
  • Lacustrine argillaceous sedimentary rocks
  • Riverine argillaceous sedimentary rocks

Marine argillaceous sedimentary rocks

                These rocks are mainly formed due to the deposition and compaction of sediments on the littoral margins of the oceans and seas. The process of sedimentation is well ordered and sequential in Character. The size of the particles decreases progressively as we go from the coastal areas towards the Centre of the sea or oceans some of the examples of these types of rocks are Limestone, sandstone, dolomite and chalk.

Lacustrine argillaceous sedimentary rocks

    These rocks are formed generally when sediments are deposited near water bodies such as Lakes. Generally the rocks are found in the floor of the Lakes. Unlike the argillaceous rocks there is no ordering of size or deposition in-Lacustrine rocks.

Riverine argillaceous Sedimentary rocks

    These rocks are formed due to the deposition of sediments in the Riverine environment. The sediments are deposited on the beds of the rivers and in the flood Plains. These deposits include alluvia which are dominated by Clay. The alluvia are deposited by rivers during floods and are renewed almost every year .These alluvial deposits develop Polygonal cracks due to their exposure to isolation.

Aeolian rocks

    They are formed due to the deposition of Sands brought out by the wind. Pre existing rocks are greatly disintegrated due to mechanical weathering and this result in the formation of large quantity of Sands of different sizes. These Particles are further comminuted in to finer Particles due to the attrition while they are being transported from one place to another. Continuous deposition results in the formation different layers but these layers are not well consolidated and hence are very porous in nature. Sometimes there is complete absence of layers in rocks such as Loess. In India loess are found on the banks of the Paleochannel and the Valley of Narmada River.

Glacial rock

    The materials deposited by the Glaciers are called glacial drifts which are deposited in four conditions and hence they are four types of morainic deposits

  • Lateral moraines- When Glacier Materials are deposited on the either Side of the Glacier.
  • Medial Moraines-When glaciers Materials are deposited along the joining of the Glaciers.
  • Ground moraines- When Glacier materials are deposited on the bed of Glaciers.
  • Terminal Moraines- These formed when glaciers are ablated and materials are deposited there.