Mood of Formation of Igneous Rock

Igneous rocks are formed by the cooling of hot magma.The grain size of magma depends on the following factors.

1.Rate of cooling:If magma cools rapidly then its molecules do not get enough time to be crystallize. Hence grain size become small.If magma cools slowly then its grain size become big.

2.Molecular concentration:If the magma is of high molecular concentration the every molecule get enough molecules surrounding it for crystallization.Hence grain size become big.If the magma is of low molecular concentration the grain size become small.

3.Viscosity:If viscosity of magma is low its molecules can  move freely and get touched with large number of molecules then the magma of high viscosity.Hence the magma of low viscosity make large grain sized igneous rock.

Factors affecting erosion and transportation

1. Nature of rock: Soft rocks show higher erosion and hard rocks show lower erosion.
2. Attitude of rock:How rocks are placed affect erosion.Inclined and horizontal rocks show greater erosion.
3. Presence of joint:Presence of joint or weak zones increase erosion.
4. Velocity of river water:High velocity of river water causes high erosion along the bank of river.
5. Land form:
   

Metamorphism

Metamorphism is the phenomenon in which heat, pressure and chemically formed liquid bring about textural,structural and mineralogical change in rocks.

Types of metamorphism:

1.Thermal metamorphism:In this case temperature predominate metamorphism.

2.Cataclastic metamorphism:Here pressure is the main factor.

3.Dynomothermal metamorphism:Both pressure and temperature are main factor.Chemically active fluid also play some important role.

4.Plutonic metamorphism:This type of metamorphism occur at some depth of earth surface where temperature is high and pressure is uniform

Types of Sedimentary Rocks

Sedimentary rocks are of following types:

1.Clastic Sedimentary rocks:These are sedimentary rocks formed by sedimentation and consolidation of the product of erosion.These are of following types
a)Argillaceous:When chief constituent is clay.e.g. Shale
b)Arenaceous:When chief constituent is sand. e.g.Sandstone
c)Silt rock:When chief constituent is silt. e.g.Siltstane
d)Rudaceous:When particles are of larger size. e.g. Conglomerate

2.Chemically formed sedimentary rock:These are formed chemically
a)Carbonate rock:When chief component is clay. e.g. lomestone .
b)Siliceous rock:When chief component is silica . e.g. flint
c)Ferruginous:When chief component is iron . e.g. some iron deposit.
d)Salt rock:Consist of different types of salts. e.g. Sodium chloride.

3.Organically formed sedimentary rock:These are formed by the agencies of organism. The products are carried by organism.Remaining of dead organism also form this type of rock.This is of following type.
a)Calcareous rock: When chief component is carbonate of Ca, Mg. e.g. limestone.
b)Siliceous rock:When chief component is silica . e.g. diatomaceous earth.
c)Phosphatic rock:When chief component is phosphate. e.g.phosphorite.
d)Ferruginous :When chief component is iron . e.g. some iron deposit.
e)Carbonate rock:When chief component is carbon. e.g. coal deposit.

Magmatic Differentiation

The process of separation of different mineral constituents from magmatic melt is called magmatic differentiation.

Types of magmatic differentiation
Magmatic differentiation is of following types:
1Gravitational differentiation: In this process earlier formed minerals get precipitated.By this minerals are disintegrated.
2Difeerentiation due to fractional differentiation:In crystallization different centers of molecules are formed.This centers attract other molecules causing separation of of magmatic materials.
3Differentiation due to liquid immiscibility:In liquid magma there are many immiscimle particles.These when cools becomes disintegrated.
4.Differentiation due to filter pressure:Earlier formed particles when get cooled they are squeezed due to compression.As a result liquid particles get out causing disintegration of minerals.(Sometimes when liquid mud get hard some crack like holes form.This is also formed when earlier mud mud particles get cooled they are squeezed due to compression.)

Importance of Geology in Civil Engeneering

1.To make foundation for dams,airports,bridges and buildings
2.For tunnel construction
3.For excavation,fills and retaining walls and harbors
4.For locating roads and highways,pipelines and canals
5.River training,embankment protection and flood control
6.For prevention and protection from landslides
7.Protection from oceanic erosion
8.For protection from earthquake
9.Protection of silting of reservoirs and harbors
10.For ground water exploration and development
11.For locating building materials

Earthquake

Earthquake is the sudden and temporary vibration of earth surface ranging from a fair tremor to a wild motion due to sudden release of energy from rocks beneath the earth surface.

Causes of earthquake
1.Non-tectonic causes:The cause that occur on the earth surface.
a)Surface cause
-large scale rock falls on the loose ground or landslide
-dashing of sea wave along coast
-water falls
-working of heavy machinery in industrial area;underground explosion of bombs;passage of tanks ; failure of dams etc.

b)Volcanic causes
-explosion of volcano with the release and expansion of hot gasses and lava.
-faulting within the volcano resulting from pressure in the chamber of malted rock.

c)Collapse of subterranean
-sometime due to removal of support from below by the reaction of underground water ground surface collapse and cause earthquake.

2.Tectonic causes
About 95% of earthquakes are due to sudden earth movement along existing or new fault. Earthquake caused by faulting or folding in the crust are known as tectonic earthquake.It can be said that the causes that occurs beneath the earth surface are called tectonic causes.This type of earthquake release huge amount of energy and cause huge damage.

Unconformities

Definition
Unconformities are defined as surface of erosion of rock separating the underlying older formation from overlying younger formation.

Formation of Unformaties
1.Deposition of older beds
2.Emergence and erosion
3.Submergence
4.Deposition of younger beds.

First older rocks are deposited in large water bodies.After sometime they are subjected to upward force due to tectonic causes(the cause occur under earth surface).This cause the distortion of older bed from its original position and emerges from water.After the emergence the rock beds are subjected to various weathering agents .These remove the top portion of the rock beds making them smooth and even.The beds then again submerge under water and new rock beds deposit on them.

Salient Charecteristics of Youth,Mature andOld Stages of River

Youth Stage
1.In this stage rivers flows through hilly region.
2.Gradient of river is high.
3.Velocity of water is high.
4.Deepening is high and effective.
5.River create deep and narrow valley.

Mature Stage
1.River emerges from hilly region to plain.
2.Gradient falls.
3.Velocity falls.
4.Deepening falls.
5River valley gradually becomes wide and depth falls.
6.As velocity falls deposition of heavier particles rises.

Old Stage
1.River flows over very flat region.
2.Deepening lower excessively.
3The river become almost flat near sea.

Weathering

The term weathering is used for disintegration and decomposition of rocks without any significant transportation of resulting product.

Weathering is of two types
1.Mechanical weathering:In this case rocks are disintegrated by physical breaking down.
2.Chemical weathering:In this case decomposition of rocks are formed by chemical reaction.Most of the reaction occurs with presence of water with different dissolving materials.

Chief weathering agents
Followings are the chief agencies responsible for weathering of rocks.
1.Atmospheric gases:The atmosphere contains CO2,O2,N2 and other gases.When these dissolve in water react with rock.
2Water:Water is an important agency.Pure water has little effect.But water with dissolved materials bring about massive changes in rocks.
3Frost:In cold regions water enter into the pores of rocks.When water becomes ice its volume expands causing disintegration of rocks.
4Heat:In hot regions rocks expand in day because of heat of sun and in night when temperature drops rocks get contracted.This develops stress causing disintegration of rocks.
5Organic agencies:Organic agencies cause both mechanical and chemical weathering.many animals dig holes in rocks for living,roots of plants forming on rocks give stress on rocks,different bacteria cause chemical reactions on rock surface etc.