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.