GEOLOGY LECTURE # 5

Metamorphic rocks:

Igneous and sedimentary rocks undergo textural and mineralogical change due to high temperature and pressure without melting. These new rocks are called metamorphic rocks.

Metamorphism:

The process of producing metamorphic rocks is called metamorphism and its mean “new shape”

Anisotropy:

The property of a rock by virtue of it has different values of physical properties in different directions.

Classification of metamorphic rocks:

Texture	Mineral content	Rock name	Original rock
Very fine grained salty texture	Minerals are too small to be seen	Slate	Shale or mud stone
Fine grained phyllitic texture(small wrinkle less)	Minerals are too small to be seen	Phyllite	Shale or mud stone
May appear very tiny visible grains	Minerals are too small to be seen	Green stone	Basalt
Medium to coarse grained schistone texture	Muscovite, biotite , chlorite, quartz, feldspar, pyroxene	Schist	Shale, mildstone, basalt
Coarse grained with pebbles from original rock	Muscovite, Chlorite, quartz, feldspar	Meta conglomerates	Conglomerates
Coarse grained with elongation and parallelism of grains	Muscovite, biotite, quartz, feldspar	Gneiss	Coarse grained igneous rock or clay and feldspar bearing sedimentary rocks
Fine to Coarse grained crystalline ganoblastic texture	Quartz , calcite, dolomite	Quartzite and marble	Sand stone (siliceous), Limestone, dolomite

*quartz is much stronger rock as compared to schist.*schist is a very weak rock it can be easily broken.

Regional metamorphism: I n this type of metamorphism high stress condition takes place over a large scale.

Thermal or contact metamorphism:  I n this type of metamorphism the changes occurred are only due to heat.whe thermal metamorphism occurs immediate near igneous intrusions it is called contact metamorphism.

GEOLOGY LECTURE # 4

Sedimentary rocks:

Rocks formed by sedimentation or accumulation and consolidation of sediments.

Weathering:

Classification of sedimentary rock:

Grades	Grain size	Rock type
Gravel or pebble	2mm and over	Conglomerates
Sand	0.1mm to 2mm	Sandstone
Silt	0.01mm to 0.1mm	Siltstone

Minerals of sedimentary rocks:

Most sedimentary rocks contain either quartz (especially siliciclastic rocks) or calcite (especially carbonate rocks). Carbonate rocks dominantly consist of carbonate minerals like calcite, aragonite or dolomite. Both cement and clasts (including fossils and ooids) of a carbonate rock can consist of carbonate minerals The stability of the major rock forming minerals (their resistance to weathering). In this series, quartz is most stable, followed by feldspar, micas, and other less stable minerals that are only present when little weathering has occurred.^[25] The amount of weathering depends mainly on the distance to the source area, the local climate and the time it took for the sediment to be transported there. In most sedimentary rocks, mica, feldspar and less stable minerals have reacted to clay minerals like kaolinite, illite or smectite.

Moh’s scale of hardness:

(based on resistance to scratch)

1.      Talc

2.      Gypsum

3.      Calcite

4.      Fluorite

5.      Apatite

6.      Orthoclase

7.      Quartz

8.      Topaz

9.      Corundum

10.  Diamond

Conglomerates:

The pebbles and gravels on consolidation and cementation produce a rock known as conglomerates.the pores of conglomerate are filled with sand,rock particle and some cementing material.

GEOLOGY LECTURE # 3

Plutonic rocks:

Plutonic rocks are formed when magma cools slowly at great depth with the retention of the volatiles. The texture of such rocks is coarse grained.

 Fissure:

A long ,narrow opening or line of breakage made by cracking or splitting, especially in rock or earth. Usually if opening b/w rock is more than 1 m then it will b called as fissure.

Joint:

A crack or fracture present in a rock is called joint. It may be vertical horizontal or inclined joint.

Faults:

A fault is a fracture along which there has been relative displacement of beds(a small litho-logical unit is called as bed).

Volcanic eruption:

The process in which the hot lava or volcanic gases comes out from a vent or fissure in the earth crust is called volcanic eruption .

Geo hazards:

"Geo hazards" are events caused by geological features and processes that cause severe threats to humans and the natural environment. Earthquakes, floods, landslides, volcanoes, avalanches, are typical examples of such events.

Fields related to geology:

1.geological engineering        2.engineering geology

 3.geotechnology                    4.geomechanics

5.tunnels                                 6.bridges

7.dams                                                8.canals

9.drains                                   10.river

11.rock slopes                         12.ports or harbors

13.foundation                          14.earthquakes                       15.ground water

Classification of igneous rocks:

Texture (essential +- accessory)	Orthoclase and quartz +- plagioclase, biotite & muscovite	Plagioclase and hornblende+- biotite, quartz, augite.	Plagioclase and augite+-olivine, hornblende	Pyroxene + hornblende	Olivine +- pyroxene
Coarse crystalline(plutonic)	Granite	Diorite	Gabbro	Peridotite	Dunite
Coarse crystalline with phenocrysts.	Pegmatatic granite	Rare or unknown	Rare or unknown	Rare or unknown	Rare or unknown
Volcanic fluid or micro crystals	Rhyolite	Andesite	Basalt	Rare or unknown	Rare or unknown
Fine  crystalline with large crystals	Porphyritic rhyolite	Porphyritic andesite	Prphyritic basalt
Galaxy	Obsidian	Rare or unknown	Rare or unknown	Rare or unknown	Rare or unknown
vasicular	Pumice		Vasicular basalt

GEOLOGY LECTURE # 2

Branches of geology:

1.    Mineralogy

2.    General geology

3.    Palentology or historical geology

4.    Petrology or petrography

5.    Economic geology: It is concerned with earth materials that can be used for economic or industrial purposes. These materials include precious and base used for economic or industrial purposes. These materials include precious and base metals, nonmetallic minerals, construction-grade stone, petroleum minerals, coal, and water.

6.    Structural geology

7.    Engineering geology

8.    Minig geology

9.    Petroleum geology

Weathering:

“it is the set of physical and biological processes that alter the physical and chemical state of rocks and soil at or near the earth’s surface.”

Or

“It is the breakdown and alteration of rocks and minerals at or near the Earth's surface into products that are more in equilibrium with the conditions found in the surrounding environment.”

Dependence:

Weathering mainly depends upon the atmospheric condition.

1.    Atmospheric condition:

2.    Erosion: It is the process of weathering and transport of solids (sediment, soil, rock and other particles) in the natural environment or their source and deposits them at any suitable place. It take place due to the action of wind, stream, rivers, glaciers, waves and landscaping etc.

3.    Deposition: It is the laying down of sediment carried by wind, water, or ice. Sediment can be transported as pebbles, sand & mud, or as salts dissolved in water. Salts may later be deposited by organic activity (e.g. as sea-shells) or by evaporation.

4.     Sedimentation: In geological sciences it is defined as the process of deposition of solid material from a state of suspension and solution of a fluid usually air or water.

Texture:

It is the description of small features of rocks.

Structure: It is the description of large features of rocks.

Rock forming minerals:

These are divided into six groups.

1.   

FELIS: LIGHT COLOUR

ACIDIC  light

Quarts:           Si.O2 (grey)----(M.P=low)

2.    Feldspar:

                      I.        Orthoclase:                (pink) K.Al.Si3.O8 (clay)

                    II.        Plagioclase:              (white) Na.Al.Si3.O8.----Ca.Al.Si3.O8

3.    Mica:

                      I.        Muscovite:     K.Al.Si3.O10

                    II.        Biotite:            K(Mg.Fe)3 AL.Si3.O10(OH)2

4.    Hornblende:  (black)

5.   

BASIC

Pyroxene:

6.   

MELFIC: DARK COLOUR

Olivine:          (Fe.Mg)2 Si.O4         (M.P=high)

Ferro-Magnesium Silicates: These are the silicates having Fe and Mg.They are dark in colour and more chemically reactive.

Properties of silicates:

Other rock forming minerals:

Carbonates calcite ca.co3 and Limestone

Rocks: In geology, rock or stone is a naturally occurring solid aggregate of minerals and or mineraloids. Types of rocks: 1.    Igneous: these are rocks that solidified directly from molten silicates, which geologists call magma. Examples are: granite, basalt, pumice and flint (which is a form of quartz). 2.    Sedimentary: these are formed by sediments or accumulation and consolidation of sediments. Examples are limestone, chalk, sandstone. 3.    Metamorphic: these are made up of igneous and sedimentary rocks of all ages which have been subjected to intense temperature and pressure. Examples are: slate, marble and quartz.