Geology,IGNEOUS,SEDIMENTARY.METAMORPHIC ROCKS

BRANCHES OF GEOLOGY:

Physical geology:

Physical geology is a branch of geology that deals with the events and materials occurring at the present time or in the near past. In this geologist have to study the current process like erosion, weathering, volcanic activities, glaciers etc.

Structural Geology:

STRUCTURE

The study of the deformation of the rocks in the earth’s lithosphere known as structural geology.

Sedimentology:

 Sedimentology deals with the study sediments, their formation, transportation and deposition

Mineralogy:

 The branch of geology which deals with the study of minerals, their formation, analysis, association, physical and chemical properties and classification is called mineralogy.

Petrology:

 The branch of geology which is concerned with the study of rocks is called petrology.

Paleontology:

 it deals with the study of fossils.

Historical Geology:

 it deals with the evolutionary history of surface and subsurface of earth. It can be done by the help of fossils study, and the events occurred in past or by the stratigraphy.

Economic Geology:

 deals with the study of material that are used to raise economy or for the industrial purpose like iron, gas, oil etc.

Engineering Geology:

 it deals with the application of geology to engineering. It concerns with the assessment of risk damages and injuries.

Hydrogeology:

 It deals with the study of groundwater movement, occurrence and suitability.

BASIC DEFINITIONS

Crystals: 

CRYSTAL

Mineral occur as a crystal, crystals are the bodies of geometric shape which are bounded by the faces arranged in a regular manner and related to internal atomic structure.

Minerals:

 it can be defined as a natural inorganic substance having particular chemical composition and a regular atomic structure.

Weathering: 

wear away or change the appearance or texture of (something) by long exposure to the atmosphere is known as weathering.

Deposition:

 the action of depositing some thing or the collection of sediments at a point is known as deposition.

Transportation:

 the action of transporting something. It may be due to wind action or water action.

Sedimentation: 

it is the tendency of the particle to remain settle as a sediment. It may be due to deposition or precipitation.

Erosion: 

it is the action in which soil removes from one location under the action of wind, water, etc. and then transport it to another location.

Valcano:

VALCANO

a mountain or hill over the earth surface which contains lava.

Lava:

 the hot fluid erupts out from the volcano.

Magma: 

the hot fluid under the surface of earth is known as magma.

Earthquakes:

 a sudden violent shaking of ground, as a result of movement of tectonic plates or volcanic action.

Diastrophism:

 Diastrophism also called tectonism. It refers to the twisting of earth surfaces.
Large scale deformation of earth crust by natural processes which leads to the formation of continents and ocean basins.

Denudation

Land areas are being reduced and their shape modified by weathering and erosion.
The general term used for this process is known as Denudation.

                                                   

   ROCK CLASSIFICATION

PHYSICAL AND MECHANICAL PROPERTIES OF ROCKS

The physical properties are also known as Index properties which describes the rock material and helps in classifying them.

The mechanical properties known as strength properties which gives information about the performance of rock material under particular loading conditions.

Rock material is generally strong in compression.

PHYSICAL PROPERTIES OF ROCKS

Mineral composition
Texture
Specific gravity
Density
Porosity
Void ratio
Moisture Content
Grain size

CLASSIFICATION OF ROCKS

IGNEOUS ROCKS

Intrusive rocks
Extrusive rocks

SEDIMENTARY ROCKS

Clastic rocks / stratified rocks
Non-Clastic rocks / un-stratified rocks

METAMORPHIC ROCKS

Foliated rocks
Non-Foliated rocks

 PROCESS INVOLVED IN ROCK CYCLE 

Crystallization
Weathering
Deposition
Erosion
Compaction
Cementation
Heat & pressure

IGNEOUS ROCKS:

The word igneous means fire. 
The rock which formed from lava or magma that one will classify in igneous rocks
Two further types
Intrusive rock
Extrusive rock

FORMATION OF IGNEOUS ROCKS:

Molten rock material which is generated below the earth’s crust reaches the surface and flows out from the volcanoes.

Sometimes that material remains within the crust in form of igneous intrusions which cools slowly and solidify.

Many of them exposed after the removal of their covering rocks by denudation.
The solidified lava and intrusions constitute the igneous rocks.

INTRUSIVE IGNEOUS ROCKS

The body of magma may rise to higher levels and penetrate the rocks above it without reaching the surface. The process is said to be intrusive

 TYPES OF INTRUSIONS

Dykes
sills
batholith
Laccolith
Phacolith

DYKES: The vertical movement of magma towards the crust not more than 3m wide.
Sills: the horizontal movement of magma towards the crust due to weight of the cover.
Laccolith: it is a type of intrusion having domed roof and a dyke.
Phacolith: it is a type of intrusion having both curved floor and curved roof.
Batholith: it is a type of major intrusion having an irregular shape.

SEDIMENTARY ROCKS:

Rock formed under the action of weathering.
Rock formed due to compaction and cementation of sediments.
These rocks are also formed due to the remains of animals and plants.
It may also form due to the action of evaporation and precipitation.

Rocks are usually formed in water. the current in the water transported the sediments and when it slows around the bends the sediments fall out because of gravity.
The larger sediments falls out first and the lightest will remain on top

TYPE OF SEDIMENTARY ROCKS:

CLASTIC ROCK:

 the rocks which formed due to process of stratification (bedding); having layers or deposition.
    example: conglomerate, sand stone, shale, silt stone.

SAND STONE

NON CLASTIC ROCK:

 the rocks which formed due to evaporation, precipitation and due to living organism is classified in non clastic.
     example: lime stone, coralline limestone, rock salt, coal

LIME STONE

EXAMPLE OF SEDIMENTARY ROCKS:

ROCK SALT

LITHIFICATION

The process of transforming loose fragmented rocks into a compact solid is known as LITHIFICATION process

TEXTURE IN SEDIMENTARY ROCKS:

The clastic rocks having three textures 

Rudaceouse (e.g. conglomerate)
Arenaceous (e.g. sand stone)
Argillaceous (e.g. shale)

Non clastic rock having 3 textures

Massive (e.g. lime stone)
Fossiloferrous (e.g. coralline limestone)
Residual deposits (e.g. bauxite)

METAMORPHIC ROCKS:

METAMORPHIC ROCK

The word metamorphism means transformation.
In this rock type the pre existing rock will transform in new rock type under the action of heat and pressure.

CLASSIFICATION OF METAMORPHIC ROCKS

Three broad classification of metamorphism:
thermal or contact metamorphism
dynamic or dislocation metamorphism
regional metamorphism


DYNAMIC METAMORPHISM: dominant property is pressure or stress. Occurs on the belts of shearing.

REGIONAL METAMORPHISM: both temperature and pressure become reasons of changes in pre existing rocks.

THERMAL METAMORPHISM: temperature is the dominant factor. Appears nearly igneous intrusion zones or when sediments are down folded in to hotter regions.

BANDING:

-FOLIATION series of parallel surface

-LINEATION: Series of parallel lines

TYPE OF METAMORPHIC ROCKS:

FOLIATED ROCKS:

 the rocks formed under the action of heat and pressure and shows bandings in the texture. Bandings may be in lineation or in foliation. It may be in different color or in the same color.

NON FOLIATED ROCKS:

 the rocks formed under the action of heat and pressure and shows the granular texture with shine on the surface.

EXAMPLES OF METAMORPHIC ROCKS:

QUARTZ:

QUARTZ

GNEISS

GNEISS

MARBLE

MARBLE