CHAPTER I: PHYSICAL GEOLOGY

1. Engineering Geology 2. Mining Geology 3. Geophysics 4. Geohydrology 5. Geochemistry

Allied Branches of Geology

1. Tectonic earthquakes 2. Non tectonic earthquakes

Cause of origin

1. Earthquakes due to superficial movements 2. Earthquake due to volcanic eruptions 3. Earthquake due to folding or faulting

Causes of earthquake

1. Depth of focus 2. Cause of origin 3. Intensity as basis

Classification of earthquakes

Mineralogy

Deals with the study of minerals. Details of mode of formation, composition, occurrence, types, association, properties uses etc. of minerals form the subject matter.8

Petrology

Deals with the study of rocks. Deals with the mode of formation, structure, texture, composition, occurrence, and types of rocks. The most important branch of geology from the civil engineering point of view.

Rossi and Ferel.

Given the Initially a scale of earthquakes intensity with ten divisions

Denudation

It is a general term used when the surface of the earth is worn away by the chemical as well as mechanical actions of physical agents and the lower layers are exposed.

Aquitard

It is partly permeable formation, which only seepage is possible and thus the yield is insignificant.

Physical weathering

It is the physical breakdown of rock masses under the attack of certain atmospheric agents.

Decomposition

It may be defined as the process of breaking up of mineral constituents to form new components by the chemical actions of the physical agents.

Disintegration

It may be defined as the process of breaking up of rocks into small pieces by the mechanical agencies of physical agents.

1. Physical Geology 2. Mineralogy 3. Petrology 4. Structural Geology 5. Stratigraphy 6. Economic Geology

Main Branches of Geology

1. Aquifers 2. Aquitard 3. Acquiclude 4. Aquifuge

Occurence of Groundwater

Economic geology

Some of the economic minerals like talc, graphite, mica, asbestos, gypsum, magnesite, diamond and gems. The details of their mode of formation, occurrence, classification. Association, varieties, concenteration, properties, uses from the subject matter.

1. Barchans or Crescent shaped dunes 2. Transverse dunes 3. Longitudinal dunes

The active dunes can be divided into three types:

earthquake

The adjustment beneath the surface however involve various crystal movements, some of which because of suddenness and intensity produce tremors in the rocks.

porosity

The amount of pore space per unit volume of the aquifer material.

Stratigraphy

The climatic and geological changes including tectonic events in the geological past can also be known from these investigations.

atmosphere

The earth is surrounded by an envelop of gases

Lithosphere

The earths crust.

Thermal effects

The effect of change of temperature on rocks is of considerable importance in arid and semi arid regions where difference between daytime and nighttime temperature is often very high. Such temperature fluctuations produce physical disintegration in a normally expected manner.

focus

The exact spot underneath the earth surface at which an earthquake originates.

bed load

The larger and heavier particles such as sands or gravels, which are moved by the winds but not lifted more than 30 to 60 cm of the earth surface.

wind

The movement of the atmosphere in a direction parallel to the earth surface.

anticenter

The point which is diametrically opposite to the epicenter.

Structural geology

The rocks, which from the earths crust, undergo various deformations, dislocations and disturbances under the influence of tectonic forces. The result is the occurrence of different geological structures like folds, fault, joints and unconformities in rocks. The details of mode of formation, causes, types, classification, importance etc of these geological structures from the subject matter.

Seismology

The science dealing with the study of earthquakes in all their aspects

zone of aeration.

The space above the water and below the surface.

Geophysics

The study of physical properties like density and magnetism of the earth or its parts.

Historical geology

The study of the earth's history through the sedimentary rock.

1. Zones of saturation 2. Zones of aeration

The subsurface occurrence of groundwater may be divided into:

1. Bed load 2. Suspended load

The total sediment load carried by a wind can be divided into two parts.

Abrasion

The wind loaded with such particles attains a considerable erosive power which helps a considerable erosive power which helps in eroding the rock surfaces by rubbing and grinding actions and produce many changes.

Aeolian deposits

These are formed as the sediments get dropped and deposited.

Barchans

These dunes that look like a new moon in plan are of most common occurrence.

Geochemistry

This branch is relatively more recent and deals with the occurrence, distribution, abundance, mobility etc, of different elements in the earth crust.

Engineering geology

This deals with the application of geological knowledge in the field of civil engineering.

Mining geology

This deals with the application of geological knowledge in the field of mining.

Geohydrology

This may also be called hydrogeology. It deals with occurrence, movement and nature of groundwater in an area.

1. Nature of rocks 2. Length of time 3. Climate

Three Factors in the process of weathering

Depth of focus

Three classes of earthquakes are recognized on this basis, shallow, intermediate and deep seated.

1. Physical or mechanical weathering 2. Chemical weathering

Two Chief Types of Weathering

1. Deflation 2. Abrasion.

Two Wind Erosion Processes

Physical Geology

Variously described as dynamic geology, geomorphology etc. It deals with different physical features of the earth, different changes occurring on the earth surface, geological work of wind, glaciers, rivers, oceans, and groundwater ands their role in constantly moulding the earth surface features and natural phenomena.

Epicenter

above the focus or origin of the earthquake

Water bearing formations

act as conduits for transmission and as reservoirs for storage of water.

acquiclude

an impermeable formation which may contain water but incapable of transmitting significant water quantities.

aquifuge

an impermeable formation neither containing not transmitting water.

Engineering geophysics

branch of exploration geophysics, which aims at solving civil engineering problems by interpreting subsurface geology of the area concerned.

interstices

can act as groundwater conduits they are of fundamental importance to the study of groundwater.

Chemical weathering

chemical reaction between gases of the atmosphere and minerals of the rocks.

Weathering

defined as a process of decay, disintegration and decomposition of rocks under the influence of certain physical and chemical agencies.

Magnitude

defined as the rating of an earthquake based on the total amount of energy released

Intensity

defined as the ratio of an earthquake based on actual effects produced by the quakes on the earth.

Groundwater hydrology

defined as the science of the occurrence, distribution and movement of water below the surface of the earth.

shallow earthquakes

depth of focus lies anywhere up to 50 km below the surface.

Secondary interstices

developed after the rock was formed.

hydrologic cycle

earth's water circulatory system.

aquifers

formations having structures that permit appreciable water to move through them under ordinary field conditions.

Sand dunes

huge heaps of sand formed by the natural deposition of wind blown sand sometimes of characteristics and recognizable shape.

intermediate earthquakes

originate between 50 and 300 km depth below the surface.

Tectonic earthquakes

originated due to relative movements of crystal block on faulting, commonly, earthquakes are of this type.

Non tectonic earthquakes

owes their origin to causes distinctly different from faulting, such as earthquakes arising due to volcanic eruptions or landslides.

Transverse Dunes

similar to a barchans in section but in plan it is not curved like barchans such that its longer axis is broadly transverse to the direction of the prevailing winds.

Capilary interstices

sufficiently small so that surface tension forces will hold water within them.

suspended load

the finer clay or dust particles which are lifted by the moving winds by a distance of hundreds of meters above the earths surface.

capillary fringe

the belt overlying the zone of saturation and it does contain some interstitial water and is thus a continuation to the zone of saturation.

soil zone

the depth from the surface, which is penetrated by the rocks of vegetation.

Longitudinal dunes

the elongated ridges of sand with their longer axis broadly parallel to the direction of the prevailing wind.

Deflation

the process of simply removing the loose sand and dust sized particles from as area, by fast moving winds.

Ground water

the underground water that occurs in the saturated one of variable thickness and depth below the earth's surface.

1. Sand dunes 2. Loess

two types of Aeolian deposits

Air currents

vertical movements of the atmosphere.

connate water

water entrapped in the interstices of sedimentary rock at the time it was deposited.

Zones of Saturation

water exists within the interstices and is known as the groundwater. Water in this zone is under hydrostatic pressure.