Chapter 1: General geology
1.1 INTRODUCTION TO GEOLOGY
works, water supply, irrigation and many
other purposes.
6. Geological maps and sections help
Geology is a branch of science dealing with
considerably in planning many engineering
the study of the Earth. It is also known as
projects.
earth science (in Greek, Geo means Earth,
Logos means Science). The study of the
earth comprises of the whole earth, its
origin, structure, composition and history
(including the development of life) and the
nature of the processes.
The role of geology in civil engineering may
briefly be outlined as follows:
Geology
provides
a
systematic
knowledge of construction materials, their
structure and properties.
2. The knowledge of Erosion, Transportation
and Deposition (ETD) by surface water helps
in soil conservation, river control, coastal
and harbour works.
is
very
necessary
they have to be suitably treated so that the
stability of the structure is greatly increased.
Pre-geological
survey
of
the
area
concerned reduces the cost of engineering
work.
1.3 DIFFERENT BRANCHES OF GEOLOGY
For studying the earth in detail, the subject
of Geology has been divided into various
branches. They are as follows:
(i) Physical Geology
As a branch of geology, it deals with the
“various processes carried out by physical
agents such as wind, water, glaciers and sea
3. The knowledge about the nature of the
rocks
beds, folds, solution channels are found,
8.
1.2 GEOLOGY IN CIVIL ENGINERRING:
1.
7. If the geological features like faults, joints,
in
tunneling,
constructing roads and in determining the
stability of cuts and slopes. Thus, geology
helps in civil engineering.
4. The foundation problems of dams,
bridges and buildings are directly related
with geology of the area where they are to
be built.
5. The knowledge of ground water is
necessary in connection with excavation
waves”. These agents go on modifying the
surface of the earth continuously. Physical
geology includes the study of Erosion,
Transportation and Deposition (ETD).
Thus the study of physical geology plays a
vital role in civil engineering as:
(a) It reveals constructive and destructive
processes of physical agents at a particular
site.
(b) It helps in selecting a suitable site for
different types of project to be undertaken
after studying the effects of physical agents.
(ii) Crystallography
rock is called historical geology. It is also
As a branch of geology, it deals with, “the
study of crystals‟. A crystal is a regular
polyhedral
form
bounded
by
smooth
surfaces.
sedimementary rocks, graphy description).
(vii) Paleontology
As a branch of geology, it deals with, the
(iii) Mineralogy
study of fossils‟ and the ancient remains of
This deals with the study of minerals.
Minerals are basic units with different rocks
and ores of the earth are made up of.
Details of mode of formation, composition,
occurrence, types, association, properties
uses etc. of minerals form the subject matter
of mineralogy.
Fossils are useful in the study of evolution
and migration of animals and plants
through ages, ancient geography and
climate of an area.
(viii) Historical Geology
study
Petrology deals with the study of rocks.
The earths crust also called lithosphere is
made up of different types of rocks. Hence
petrology deals with the mode of formation,
structure, texture, composition, occurrence,
and types of rocks.
of
both
stratigraphy
and
paleontology”. Its use in civil engineering is
to know about the land and sea, the climate
and the life of early times upon the earth.
(ix) Economic Geology
Minerals can be grouped as general rock
forming minerals and economic minerals.
(v) Structural Geology
Some of the economic minerals like talc,
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.
graphite,
mica,
asbestos,
gypsum,
magnesite, diamond and gems.
(x) Mining Geology
This deals with the application of geological
knowledge in the field of mining. A
mining engineer is interested in the mode
(vi) Stratigraphy
and extent of occurrence of ores, their
The climatic and geological changes
tectonic
plants and animals are referred to as fossils.
As a branch of geology, it includes “the
(iv) Petrology
including
called stratigraphy (Strata = a set of
events
in
the
geological past can also be known from
these investigations. This kind of study of
the earth’s history through the sedimentary
association, properties etc..
(xi) Civil Engineering Geology
As a branch of geology, it deals with “all the
geological problems that arise in the field
of civil engineering along with suitable
• The deepest whole in the earth is only
treatments”.
about 8km, this is quite negligible in
Thus,
it
includes
the
construction of dams, tunnels, mountain
roads, building stones and road metals.
comparison with radius of the earth
• The internal structures of earth is based on
(xii) Hydrology
the
As a branch of geology, it deals with “the
existence
yield
at
by
indirect
geophysical method (seismic method)
studies of both quality and quantity of
• The earth body comprises of several layers
water that are present in the rocks in
which are like shells resting one above the
different states”(Conditions). Moreover, it
earth
includes: (a) Atmospheric water, (b) Surface
water, and (c) Underground water.
• The layers are distinguished by the
physical and chemical properties
(xiii) Indian Geology
• The interior of the earth has been obtain
As a branch of geology, it deals with “the
from the study of earthquakes waves
study of our motherland in connection
through the earth There are three types of
with the coal/petroleum, physiography,
waves.
stratigraphy and economic minerals of
India”.
They
are
P-waves/Primary
waves/Longitudinal waves:
(xiv) Resources Engineering
 The waves travel in solid, liquid and
As a branch of geology deals with “the
study of water,
land,
solar energy,
minerals, forests, etc. fulfill the human
wants”.
gaseous medium.

They
have
short
and
frequency.
S-waves/Secondary
(xv) Photo Geology
wavelength
waves/Transverse
waves:
As a branch of geology deals with “the
study of aerial photographs”.
 These waves travel in solid medium.
 They have short wavelength and high
frequency.
L-waves/Surface waves/Rayleigh waves:
1.4
EARTH’S
STRUCTURE
AND
COMPOSITION:
• Direct observation of earth is not possible
due to fact that the interior became hotter
 These are transverse waves and confined
to outer skin of crust.
 These waves responsible for most of the
Upper
destructive coarse of earthquake. The shell
Mohorovicic discontinuity down to 400
of the increasing density are found towards
km is referred to as the upper mantle. A hot
the centre of the earth is 80g/cc. Each shell
envelope of semi-molten materials whose
is formed off different materials on the
top parts are semi-solid (Asthenosphere). Its
basics of seismic investigation the earth
general composition consists of Silica and
interior has been broadly divided into three
Magnesium rich minerals (i.e.: SIMA). The
major parts,
Outer Mantle is usually traversed by huge,
fragmentation
Crust -The crust is the near surface layer
with variable thickness (5-50 km). The crust
in the oceanic region is considerably thinner
than the crust in the continental region and
remarkably
-The
layer
below
the
but slow convection currents that result in
 Crust  Mantle  Core
is
Mantle
homogeneous
with
a
thickness of 6 km. In contrast, the thickness
of continental crust is highly heterogeneous.
of
the
overlying
crustal
plates.
Lower mantle -A hot envelope of molten
materials and It is general composition
consists molten Si + Mg rich minerals (i.e.:
SIMA). The Inner Mantle is usually of more
temperature than the above shell.
It can be divided into two layers  Upper
Core -The core has two layers: an inner
layer (continental crust)  Lower layer
core that is solid and an outer core that is
(oceanic crust)
liquid. The core is mostly iron, with some
Mantle -The mantle is the thickest of
Earth‟s layers and takes up 83% of the
Earth‟s volume. It extends down to about
nickel and takes up 16% of Earth‟s total
volume. The core is divided into two parts.
They are
2900 km from the crust to Earth‟s core and
Outer Core -A very hot envelope of strongly
is largely composed of a dark, dense,
molten materials. It is mainly composed of
igneous rock called “peridotite‟, containing
molten SIMA as well as some S, Ni and Fe.
iron and magnesium. The mantle has three
Due to the great overlying pressure, this
distinct layers: a lower, solid layer; the
part behaves as solid, however, it is a real
asthenosphere, which behaves plastically
melt, so the short waves suffer a great
and flows slowly; and a solid upper layer.
reduction in the velocities in this part.
The upper mantle and the crust make up
the lithosphere, which is broken up into
pieces called “plates‟, which move over the
asthenosphere. The interaction of these
plates
is
responsible
for
earthquakes,
volcanic eruptions and the formation of
mountain ranges and ocean basins.
Inner Core -A very hot envelope of strongly
molten materials. It is entirely composed of
molten Ni and Fe, the same as meteorites.
Due
to
the
very
excessive
overlying
pressure, this part behaves as solid, so the
short waves display increase in velocities in
this part.
1.5 ELEMENTARY KNOWLEDGE ON
CONTINENTAL DRIFT AND PLATE
TECTONICS
Two Kinds of Crust
Continental Crust - the part of the crust
that makes up the earth’s surface. About
The Continental Drift Theory was developed
in the early 20th century. It was proposed by
Alfred Wegener. Wegener is a German
meteorologist and geophysicist that
formulated the first complete statement
about the continental drift theory.
The continents were once a single
supercontinent called Pangaea, which is
Greek for all earth. Then broke apart into
two supercontinents called Laurasia and
Gondwanaland. He proposed that the
continents are where they are now after
Pangaea broke millions of years ago. He
called this the Continental Drift.
The evidence for continental drift included:
1. The puzzle-like features of the outlines of
the continents that can fit together,
2. The distribution of ancient fossils, rocks,
and mountain ranges;
3. The locations of ancient climatic zones.
40% of the
surface of the earth is made up of this
layer.
Oceanic Crust - the component of the
earth’s crust that makes up the ocean
basins.
The entire lithosphere of the Earth is
broken into numerous segments called
plates.
Earth has seven major tectonic plates:
Earth has seven major tectonic plates:
1. Pacific Plate
5. Antarctic Plate
2. North American Plate
6. Indo-Australia Plate
3. Eurasian Plate
7. South American Plate
4. African Plate
Mantle Convection and Plate Motions
The distribution of fossils, rocks, and
mountain ranges.
Plate Tectonic
What is Plate Tectonics?
Plate tectonics is a scientific theory that
explains how major landforms are created
as a result of
Earth’s subterranean movements.
Crust - In geology, the outermost layer of
the Earth.
What force is great enough to move the
continent?
Plates Motion Over Time
Scientists used satellites to measure plate
motion precisely. The plates move very
slowly – from about 1 to 12 centimeters
per year. The North American and
Eurasian plates move apart at a rate of
2.5 cm per year.
Type of Plate Boundaries
1. Divergent Plate Boundaries
The two plates move away from each other.
Can a crack in Earth’s crust be so wide that
people can walk through it? In Iceland, it
can!
2. Convergent Plate Boundaries
The two plates move toward each other.
The Andes mountains run for 8,900 km
along the west coast of South America.
3. Transform Plate Boundaries
The two plates slide or grind past each
other without diverging or converging.
The best example of this plate is the San
Andreas fault which is bounded by the
North American plate and the Pacific
plate.
the atmosphere. Such an altered product is
known as weathered material and the
process involved is called weathering.
Weathering and erosion constantly change
the Earth. Weathering wears away exposed
surfaces over time.
Agents of weathering There are several
methods
by
which
rocks
undergo
weathering. These may be broadly classified
under two main classes:
 Physical (Mechanical) Weathering
 Chemical Weathering.
 Biological Weathering
Physical Weathering -It is a natural
process of disintegration of rocks into
smaller fragments and particles without
inducing any chemical change in the end
product. A single rock block, for instance,
1.6 Earth Processes
Earth Processes are dynamic actions that
take place within the earth or on its
surface. Processes can be slow or fast.
The Earth's natural forces can be divided
into two groups:
may
be
disintegrated
gradually
into
numerous small irregular fragments which
in turn may break into particles of still
smaller dimensions.
a) Frost Action -As is known, water on
freezing undergoes an increase in its
volume by about ten percent.
Constructive Earth Processes – any
b) Thermal Effects -There is another
process that builds earth forms.
process of physical breakdown of rocks
Destructive – any process that destroys
earth forms.
1.7 WEATHERING
The physical and chemical conditions of
rocks are altered when they are exposed to
under direct slow heating (followed by
cooling) of the exposed rocks by the blazing
sun.
1. Spheroidal Weathering -Rocks, like
many other solids, expand on heating and
contract
on
cooling.
Phenomenon
of
peeling off of curved shells or layers from
not always end in the formation of a stable
rocks under the influence of thermal effects
end product. Often they result in splitting of
in association with chemical weathering is
particles into still smaller particles – the
often termed as exfoliation.
colloids – characterized by atoms with only
2. Exudation is a process similar to frost
action but in this case disintegration takes
place due to formation of crystals of salts
like sodium chloride etc. within the cavities.
The process is seen in rocks near shores.
partially
satisfied
electrical
charges.
Formation of colloidal particles is especially
common in the weathering of clay minerals,
silica and iron oxides.
(e) Carbonation -It is the process of
Chemical Weathering -It is a process of
alteration of rocks of the crust of the Earth
by chemical decomposition brought about
weathering of rocks under the combined
action of atmospheric carbon dioxide and
moisture.
by atmospheric gases and moisture.
Biological weathering
(a) Solution -Some rocks contain one or
Role of Plants and organisms -It is a well
more minerals that can be removed in
known fact that plants and organisms also
solution by water. Rock salt, gypsum and
cause
calcite are a few common examples.
disintegration of rocks of the crust. Plants
(b) Hydration and Hydrolysis -First : The
process of addition of water molecules is
termed hydration. Examples : In some
considerable
decomposition
and
Hydrogen (H+ ) ions are known to be
released at the roots of plants due to their
growth and metabolism.
minerals with ferrous ion, the Fe++ ion
1.8 WORKS OF RIVERS, WIND AND SEA
holds the water molecule to form a water-
AND THEIR ENGINEERING IMPORTANCE
iron complex or a hydroxide. Similarly,
CaSO4 or anhydrite, gets slowly converted
to gypsum by hydration.
Sources of stream water -Most of the
water flowing as rain or snow on the surface
tends to flow directly or indirectly into the
(c) Oxidation and Reduction -Iron is a
sea. The greater parts of precipitation
chief constituent of many minerals and
continues its seaward journey superficially
rocks. These iron containing materials are
that is flowing right over the surface of the
especially
susceptible
earth.
weathering
through
the
to
chemical
processes
of
oxidation and reduction.
Sub-surface water -A good part of rain
water and melt water is absorbed by the soil
(d)Colloid Formation -The process of
and rocks of the surface and starts its
hydration, hydrolysis and oxidation (and
seaward journey below the surface of the
reduction) acting on rocks and minerals
earth. The water that has infiltrated into the
under various atmospheric conditions may
earth is called sub-surface water.
There are three stages of the river:
1. Youthful stage -The most dynamic of all
rivers is a youthful river. It is
characteristically found at higher elevations,
in mountainous areas, where the slope of
the land is steeper. Water that flows over
3.Old stage -In this stage, river cannot
have its own dynamic behavior. During
flood stages, water that overflows the river
bank, pouring over and beyond levees,
attains velocities not only capable of
moving large boulders.
such a landscape will flow very fast.
The observations of an old river are:
The observations of a youthful river are:
 The river flows down a very shallow
 The river flows down a steep gradient and
erosion is prominent over deposition.
 The channel is deeper than it is wide and
V-shaped due to down-cutting rather than
lateral (side to side) erosion.
gradient
 The channel is wider than its deep with a
very broad and U-shape due to extensive
lateral erosion.
There are four main processes of erosion
that occur in rivers:
 Capable of moving all sediment sizes from
ions in solution, to silt and clays and also
cobbles and pebbles.
1. Hydraulic action
 It is the mechanical loosening and removal
 Rapids may be present due to the water
of the material from the rock through
velocity and the presence of boulders in the
pressure exerted by running water.
channel. Waterfalls are also a feature of a
young river.
 Higher velocity greater is the pressure of
running water to bodily move out parts of
2. Mature stage -The river is in middle
the rock or grains of soils from the parent
stage of its journey. The river still downcuts
body
though to a much lesser degree than the
youthful stage does but it also erodes
laterally, though not as extensively when
compared to the old stage.
The observations of a mature river are:
 The river flows down a moderate gradient
 Joints fissures cavities cracks are helpful to
the running water in carrying out hydraulic
action.
2. Abrasion / Corrasion
 The flowing water uses rock fragments
such as pebbles, gravels and sands as a tool
 The channel is U-shaped and wider than a
for scratching and grinding the sides and
youthful river yet deeper than an old age
floor of the riverbed.
channel due to moderate down cutting but
also lateral (side to side) erosion.
 It is a slow method involving loosening,
been loosened by erosion may be then
disintegrating, rubbing, grinding &
transported along the river.
polishing the rock fragments.
There are four main processes of
 It is capable of eroding & smoothening
even the hardest rock.
3. Attrition
 This term refers to wear & tear of the load
sediments being transported by a moving
natural agent through the process of mutual
transportation:
1. Suspension / suspended load
Suspension is when material made up of
very fine particles such as clay and silt is
lifted as a result of turbulence and
transported by the river.
impacts and collision which they suffer
2. Solution / solution load Solution load is
during their transport.
when dissolved material is carried by a river.
 The attrition causes the rock fragments to
become more rounded and smaller in size.
 The variation in size of sand particle is
2mm to 0.6mm
This often happens in areas where the
geology is limestone and is dissolved by
slightly acidic water.
3. Saltation is when material such as
pebbles and gravel; that is too heavy to be
carried in suspension is bounced along the
4. Corrosion
 It includes the solvent and the chemical
action of water on country rocks. The
chemical decay works along joints and
river by the force of the water.
4. Traction is when large materials such as
boulders are rolled and pushed along the
river bed by the force of the river.
Works of wind
cracks and thus helps in breaking the bed
rocks.

gases collectively known as air.
 Carbon dioxide dissolves in the river to
form a weak acid. This dissolves rock by

rocks such as limestone and chalk are
evident in a channel.
Transportation
Transportation of material in a river begins
when friction is overcome. Material that has
Air in motion is called wind  Wind
is one of the major geological
chemical processes.
 This process is common where carbonate
Atmosphere is composed chiefly of
agents of change on the surface

Winds create temporary or
permanent changes on the land
surface depending on wind volume,
wind velocity, nature of the surface,
duration for which the wind blows
and so on.


Strong winds blowing over loose
alluvium or locally removed by sheet
ground and dry soils and deserts
erosion, stones too large to be
may create many features within
moved become concentrated at the
short span of time
surface.
Wind acts as agent of erosion as a
carrier for transportation of particles
and grouirs and then deposit huge
quantities at different places.
(c) Dreikanter

formed in deserts or periglacial
environment due to abrasive action
Wind Erosion
1. DEFLATION:( TO BLOW AWAY)
of wind.

covered with vegetation.
2. Wind moving with sufficient velocity
(d) Hammada

sand has been blown away by strong
ground covered with dust, its
material from the surface known as
winds.


In some desert deflation may
remove the sand from a particular
distance in deserts.
2. ABRASION

of which is virtually touching the
equipped with sand & dust particles.


Oasis is defined as much deeper and
extensive depressions intersect by
water table and partially filled up
with water.
(b) Desert Pavement

When sand and dust are either
blown away from a deposit of
This load is acquired by the strong
winds quite easily while blowing
water table and such depression is
known as blow outs.
Wind is a powerful agent for eroding
wear off the rock surfaces when
location to such an exert depression
(ie) small or great is created the base
It is also a desert pavement
extending for a considerable
deflation.
(a) Blowout and Oasis
It is bare rock surface ( found in
desert) from which thin cover of
over dry and lace sands or bare
remove huge quantity of the
It exhibit a characteristic 3 faced
pyramidal shape.
1. Wind possesses not much erosive
power over locks or over the ground
It is a type of ventifacts that typically
over sand heaps and loose dry soil.

This type of erosion involves
polishing and eroding of rock
surface by a national agent known as
abrasion.
(a) Ventifacts

These are small sized rock fragments
 Their path is determined by their density
having one,two,three or more
and velocity of the wind
polished faces

The polishing of the sides of the
originally rough fragments is carried
out by prolonged wind abrasion on
the surface of each fragment.

After one faces is plashed a second
face is made available to the wind
action by overturning of the
fragments during gushes of wind

These wind polished & facetted
fragments are called ventifacts.
(b) Pedestal or Mushroom Rocks
 It moves in Zig-Zag paths
 The wear& tear of load sediments
suffered by them due to mutual impacts
during transport is Attrition.
1.9 ORIGIN, OCCURRENCE OF
EARTHQUAKE
Origins Of Earthquakes
What is an earthquake?

It is known as mushroom rocks

They flat topped rock masses that
An earthquake is the shaking of the
ground caused by sudden motions along
faults, or fractures in
are characterized with slender lower
the earth’
region

The top is commonly referred as
The earthquakes originate in tectonic plate
overhang and the support as
boundary. The focus is point inside the
pedestal. They are generally few
earth where the earthquake started,
meters in height.
sometimes called the hypocenter, and the
(c) Yardangs

It is an elongated low lying ridges
forming overhangs above
depression

Yardangs occasion groups

Yardangs are formed in area where
rocks of alternate hard and soft rock
lying one over other with gentle
slope.
3. Attrition
 The sand grains and other particles that
are lifted by the winds and carried away do
not travel in a straight path
point on the surface of the earth directly
above the focus is called the epicenter.
Earthquakes also originate from a volcanic
eruption, bomb blasts, landslides, or
anything else that suddenly releases
energy on or in the Earth.
Two ways to measure the strength of an
earthquake:
1. Magnitude is proportional to the
energy released by an earthquake at
the focus. It is calculated from
earthquakes recorded by an instrument
called seismograph. It is represented by
Arabic Numbers (e.g. 4.8, 9.0).
2. Intensity is the strength of an
earthquake as perceived and felt by
people in a certain locality. It is a
numerical rating based on the relative
effects to people, objects, environment,
and structures in the surrounding. The
intensity is generally higher near the
epicenter. It is represented by Roman
Numerals (e.g. II, IV, IX).
Occurrence of Earthquakes
Earthquakes are usually caused when
underground rock suddenly breaks and
2.0 MODE OF OCCURRENCE
The modes of occurrence of elements in
coal are an important basic concept in
coal geochemistry and coal geology and
have been applied to a broad range of
studies.
Also, modes of occurrence of an element
provide valuable clues as to the origin of
the element;

the geochemical processes that the
precursor peat and coal have
undergone; and

how the element will behave upon
coal cleaning, utilization, leaching,
disposal.
there is rapid motion along a fault. This
sudden release of energy causes the
seismic waves that make the ground
shake. During and after the earthquake,
the plates or blocks of rock start
moving—and they continue to move until
they get stuck again. The spot
underground where the rock first breaks
is called the focus, or hypocenter of the
earthquake. The place right above the
focus (at the ground surface) is called the
epicenter of the earthquake.
There are two types of earthquakes:
1. Tectonic earthquakes –
are produced by sudden
movement along faults
and plate boundaries.
2. Volcanic earthquakes earthquakes induced by
rising lava or magma
beneath active volcanoes.
Mode of Occurrence of minerals
Minerals are usually found in ores. The
term ore is used to describe an
accumulation of any minerals mixed with
other elements.
The ores determine the cost of extraction
and it is important to understand the main
types of formation in which mineral occur.
Minerals generally occur in these following
forms:
a) In igneous and metamorphic
rocks minerals may occur in
the cracks, faults or joint. The
smaller occurrences are called
veins and the larger are called
lodes. Major metallic minerals
like tin, copper, zinc and lead
etc. are obtained from veins
and lodes.
b) In sedimentary rocks a
number of minerals occur in
beds or layers. They have
been formed as a result of
deposition, accumulation
and concentration in
horizontal strata.
c) Another mode of
formation involves the
decomposition of
surface rocks, and the
removal of soluble
constituents, leaving a
residual mass of
weathered material
containing ores.
d) Certain minerals may occur as
alluvial deposits in sound of
valley floors and the base of
hills.
e) The ocean water contains
vast quantities of minerals
to be economic significant.
Common salt, magnesium
and water. The ocean beds
too are rich manganese
nodule.
2.1 PROSPECTING
Prospecting means exploring for
minerals to a depth of fewer than 2 meters
below the surface of the earth of any preexisting excavation by means of a handheld instrument. It is the stage of
geological analysis. It is the exploration of
territory and the search for minerals,
fossils, precious metals, or mineral
specimens.
Types of prospecting
1. Traditional
Prospecting
–
its
prospectors were looking for a simple,
easy-to-find mineralization- native gold in
stream gravels or in veins out copping on
the rocky sides of the mountains.
2. Modern Prospecting – the modern
prospector is a member of a team of
highly trained specialists who use
sophisticated equipment in a planned,
systematic search. The team generally
includes experts in geology, geophysics,
geochemistry,
computer
techniques,
drilling, mineral economics, metallurgy,
and related fields.
Prospecting method
1.
2.
3.
4.
5.
Direct method
Geochemical Method
Biochemical Method
Geobotanical Method
Remote Sensing
2.2 GROUND WATER
HYDROLOGIC CYCLE: There is a natural
cycle of water on the surface of the earth.
This is called Hydrologic cycle.
The cycle consists of the following parts:
(a) EVAPORATION: Evaporation occurs
when the physical state of water is changed
from a liquid state to a gaseous state.
(b) CONDENSATION: Condensation is the
process by which water vapor changes it's
physical state from a vapor, most
deposition. This is called connate
commonly, to a liquid. Water vapor
water.
condenses onto small airborne particles to
form dew, fog, or clouds.
(c) PRECIPITATION: The clouds are
condensed on the mountains producing
rain.
TWO ZONES OF GROUND WATER
1. The lower zone is called zone of
saturation. Here all the openings in rocks
are completely filled with water. The
uppermost level of this zone is called water-
(d)SURFACE RUN OFF: Part of rain water
flows on the surface in the form of rivers
and reaches back the sea.
table.
2. The upper zone is called zone of
aeration. Here, the openings are filled
(e) INFILTRATION: Part of the rain water
partly with water and partly with air. This is
penetrates into the ground and is stored up
also called Vadose Zone.
in the open spaces of rocks. This is called
groundwater.
(f) TRANSPIRATION: The groundwater is
absorbed by the roots of plants and is again
let off in to the atmosphere as vapour
through the leaves.
OCCURRENCE OF GROUND WATER
Ground water is a part of rain water
penetrates into the ground. The rocks
immediately below the ground surface
contain openings and cracks. They are filled
up by this water. This is called groundwater
or subsurface water.
Sources of groundwater
1. Rain water (meteoric water) is the
chief source of groundwater.
2. Sometimes, hot water may be
contributed by deeper magmatic
sources. It is called juvenile water.
3. The pores in sedimentary rocks
contain water trapped during
Volume percentage of pore spaces in rock is
called porosity.
The speed of passage of water through the
rock is called permeability.
Aquifer - a saturated geologic unit that can
store enough water and transmit it fast
enough under ordinary to be hydrologically
significant.
Aquifuge - a rock that neither transmits nor
stores water.
Aquiclude - a geologic unit that only stores
water but does not transmit enough water
Aquitard - a unit that stores and transmits
water fast enough to be hydrologically
significant but insufficient for well
production.
TYPES OF AQUIFER
Unconfined aquifers are those into which
by solution as descending water enlarges a
crack in limestone
water seeps from the ground surface
• Karst topography: an area with many
directly above the aquifer.
sinkholes and with cave systems beneath
Confined aquifers are those in which an
the land surface.
impermeable dirt/rock layer exists that
2.3 IMPORTANCE OF GEOLOGY IN CIVIL
prevents water from seeping into the
ENGINEERING
aquifer from the ground surface located
directly above.
Before constructing roads, bridges, tunnels,
tanks, reservoirs and buildings, selection of
Perched aquifer will occur when low-
site is important from the viewpoint of
permeability materials interbed with higher
stability of foundation and availability of
permeability units, causing downward
construction materials. The geology of an
percolating water to form a perched
area, rock-forming region, their physical
saturated lense in the zone of saturation.
nature, permeability, faults and joints, etc
SPRING
When groundwater issues out on the land
surface on its own accord, it is called a
spring. A spring is formed whenever watertable cuts the land surface.
EFFECTS OF GROUND WATER
• caves (or caverns): naturally formed
underground chamber
• Stalactites: icicle-like pendants of
dripstone hanging from cave ceilings,
generally slender and are commonly aligned
along cracks in the ceiling, which act as
conduits for ground water • Stalagmites:
cone-shaped masses of drip-stone formed
on cave floors, generally directly below
stalactites
• Sinkholes: closed depressions found on
land surfaces underlain by limestone; they
form either by the collapse of a cave roof or
are important. Thus, geology is related to
civil engineering construction jobs with
economy and success.