basic-geology-unit 1.pptx

ENGINEERINGGEOLOGY(21CE201)
UNIT 1
Physical Geology

ENGINEERING GEOLOGY
• Engineering geology is the application of geology for safe
and economic design.
• Engineering geological studies may be performed during the
planning, environmental impact analysis, civil or structural
engineering design, value engineering and construction phases of
public and private works projects, and during post-construction and
forensic phases of projects.
• Soil/Rock deformability pattern, stability are main concern o
f
Engineering Geology.

HISTORY OF ENGINEERING
GEOLOGY
 The first book entitled Engineering Geology was published in 1880 b
y William
Penning.
 The first American engineering geology text book was written in 1914 by Ries and
Watson.
 The need for geologist on engineering works gained world wide attention in 1928
with the failure of the St. Francis dam in California and the loss of 426 lives.
 More engineering failures which occurred the following years also prompted
the requirement for engineering geologists to work on large engineering
projects.

IMPORTANCE OF ENGINEERING GEOLOGY IN
DEVELOPMENT
• To recognise potential difficult ground conditions prior to detailed
design and construction
• It helps to identify areas susceptible to failure due to
geological hazards.
• To establish design specifications
•
To have best selection of site for engineering purposes
•
To have best selection of engineering materials for construction

Geology in Civil Engineering
Design
Some of the geological characters that have a direct or indirect bearing
upon the design of a proposed project are:
(i) the existence of hard bed rocks and their depth from and inclination.
(ii) The mechanical properties along and across the site of the
proposed project.
(iii) Presence, nature and distribution pattern of planes
of structural weakness.
(iv) The position of ground water table in totality.
(v) Seismic character of the area as deciphered from
the seismic history and prediction about future seismicity.

Construction
• The engineer responsible for the quality control of construction
materials will derive enormous benefit from his geological background of
the nature material such as sand, gravel, crushed rocks.
• Similarly for construction in geologically sensitive areas as those of
coastal belts, seismic zones and permafrost regions, knowledge of
geological history of the area is of great importance.
• Construction of underground projects like tunnels cannot at all be
undertaken without a through knowledge of the geological characters and
setting of the rocks and their relevance to the loads imposed.

AREA COVERED BY ENGINEERING GEOLOGY
 Geological Hazard (landslide, slope stability, erosion, flooding,
dewatering, seismic studies)
 Geotechnical
 Material Properties
 Landslide & Slope stability
 Erosion
 Flooding
 Dewatering
 Seismic Studies Etc.
 Most important roles of the engineering geologist is the interpretation o
f
landforms and earth processes to identify potential geologic and related
man-made hazards that may impact civil structures and human
development.

Branches of Geology
Main branches Allied branches
• Physical geology
• Mineralogy
• Petrology
• Structural geology
• Historical geology
• Paleethnology
• Economic geology
• Engineering geology
• Mining geology
• Geophysics
• Geohydrology
• Geochemistry

Physical geology
• A study on the physical aspects of geology, including rocks and
minerals, plate tectonics, earthquake, volcanoes, glaciation,
groundwater, streams, coasts, climate change, planetary geology.
• It includes origin, development and various surface features of the
earth and also its internal structure
• Role played by internal agents (volcanism and earthquakes) and
external agents (wind, water and ice).
• Deposition of rock bodies, water bodies and huge deposits of ice on
the surface and their structures.

Geomorphology
• Study on the surface features of the earth.
• It include the development and disposition of mountains, plains,
plateau, valleys and basins.
• Structure and evolution of landforms through space and time.
Mineralogy
• Deals with the formation, occurrence, aggregation, properties and uses of
minerals.
• Crystallography: Internal structure and external manifestation of minerals.

Petrology
1. Petrology deals with the study of rocks.
2. Minerals occurring in natural aggregate forms are called rocks
3. Formation of varies rocks, mode of occurrence, composition,
texture and structure, geological and geographical distributions
4. Igneous: formed from melted rock deep inside the earth,
Sedimentary: formed from the accumulation of sand, silt, dead
plants and animal skeleton,
and metamorphic: formed from other rocks that are changed by
heat and pressure underground.
Petrology deals with the nature and distribution of rocks

Historical geology
1. Past history of earth
2. Study of fossils
3. Evidence about the climates, biological and environmental
conditions prevailing just before, during and after formation
of these rocks in and around the areas of their occurrence.

Economic geology
1. Economic geology focus on earth materials that can be used for
economic development purpose.
2. Study of minerals and rock occurring on and in the earth that can
be exploited for the benefit of man.
3. Formation and accumulation, their properties, structural and
other aspects that help in their extraction at economic costs.

Structural geology
1. It deals with how the rocks deforms in response to the stresses
that act within earth.
2. The rocks from earth’s crust, undergoes various deformations,
dislocations and disturbances under the influence of tectonic
plates.
3. The result is the occurrence of different geological structures,
mode of formation, causes, types and classifications.

Allied Sciences
• Geochemistry: Chemical constitution of earth, distribution and relative
abundance of different elements.
• Geophysics: A study of the physics of the earth and its environment in
space. Identification of water and oil bearing strata below the surface.
• Mining geology: Exploration and exploitation of economic mineral
deposits.
• Location and development of mines.

• Geohydrology: Interaction between hydrology and geology.
• Geological aspects of groundwater and surface water bodies
related to their occurrence and movements through different
types of rocks.
Engineering geology:
• Includes Geotechnical studies of sites.
• Availability of materials and requirement for the constructions
• Planning, design and construction of safe, stable and economic
engineering projects.

ROAD DAMAGE DUE TO SHINKAGE
OF SUBSOIL

ROAD DAMAGER DUE TO SMALL
RAIN

SMALL BRIDGE WASH OUT DUE TO LACK OF PROTECTION
WORK
LOOSE SOIL

ROAD CONSTRUCTED ON
SLOPE WASH MATERIAL WITH
UNPROPER PROTECTION

LOSS DUETOLACK OF
SAFETY AWERNACE
SLIDE DUE TO
FLOOD
DANGER ZONE

WHY THIS HAPPENED SOLUTION
 POOR SUBSURFACE
CONDITION
 LACK OF SAFTY MEASURES
 LACK OF AWARENESS
 STRUCTURE CONSTRUCTED
WITHOUT PROPER STUDY
OF DEFORMABILTY.
 STUDY OF AREA IN VIEW OF
SOIL-SUBSOIL NATURE FOR
CONSTRUCTION, SAFETY AND
REMEADY MEASURES
INCLUDING ECONOMICAL
VALUE BEFORE FINALIZE THE
PROJECT.
 FOR STUDY THE NATURE OF
SOIL-SUBSOIL AND ITS
CONSTRUCTION PROPERTIES
COMES UNDER ENGINEERING
GEOLOGY

CAREER IN ENGINEERING GEOLOGY
Infrastructure Projects as Hydro Power Plant, Tunnels for
railway/transport, Canal, Dam, reservoir, highways, bridges,
buildings, water treatment plant, land use, environmental studies
etc.
 F o r Mine and Quarry excavations, minereclamation.
 F o r coastal engineering, sand replenishment, water front
development.
 F o r offshore drilling platform, sub sea pipelinea
n
d
cables etc.

Weathering:
Introduction
When rocks become exposed at the earth’s surface, they begin to
be weathered away. Weathering agents, such as water, wind, and
ice, shape the landforms we see.
Weathering refers to the changes in rocks at or near earth’s surface
as they are exposed to the atmosphere, water, or
organisms. Weathering can occur by physical or chemical
processes and depends on the climate and other factors. Soil is
formed by weathering processes.
1. Physical weathering
2. Chemical weathering
3. Climate and weathering
4. Soil development

 Composition and
structure of rock
 Nature of ground slope
 Climatic variations
 Floral effects

 Wind
 Glacier
 Running water
 Sea waves
 under ground
water

1. Physical
weathering
2. Chemical
weathering
3. Biological
weathering

Physical Weathering
• Physical weathering occurs when rocks are broken into smaller
pieces with no chemical changes. Physical weathering is also
called mechanical weathering or disintegration. Several
processes cause physical weathering including: frost
action, exfoliation, and organic activity.
• Frost Action and Temperature Changes
• Frost action occurs when water freezes and expands in open
spaces in rocks, pushing fragments apart.
• Daily or seasonal heating and cooling causes rocks to expand and
contract, breaking them along grain boundaries.

 Also known as mechanical
weathering.
 It is caused by the change
temperature.
 Due to expansion and
contraction rocks break up.

Physical weathering happen due to
the process of,
 Changing of temperature
 Freezing action of water
 Roots growing plants which
disintegrate rocks

Exfoliation
• Exfoliation is caused
by the expansion of
rocks when pressure is
released as overlying
rocks are eroded
away. Exfoliation
creates curved surfaces.

In the left photograph, frost has lifted soil grains and sticks off the
ground. In the right photograph, ice has formed along the bedding
planes at a cliff in Radford. Expansion of water as it freezes helps to
break rocks apart.

Organic Activity
• Organic activity, or
activity by plants and
animals, can also cause
physical
weathering. Tree roots
that grow into crevices
and small animals that
burrow can cause
physical weathering.
These tree roots are wedging rocks
apart. Tree roots along cliff faces or
steep slopes can cause rocks to
weather out and fall or slide.

 Decomposition and
disintegration of rocks due
to chemical reaction.
 Water causing a change in
the chemical composition of
rocks.

1.Solution
 It is refers to the dissolution of soluble
particles and
minerals from the rocks.
2.Oxidation
 It is a reaction of atmospheric oxygen
to form oxides.
3.Carbonation
 It is a reaction of carbonate or
bicarbonate ions with minerals.
4.Hydration
 The process of hydration is related to
the addition of water to the minerals.

Chemical Weathering
Chemical weathering, or decomposition,
changes original rocks into new material with
different compositions. Several processes
cause chemical
weathering: dissolution, hydrolysis,
and oxidation.
 Dissolution
• In dissolution, water breaks down mineral
grains into the elements that make them up.
Natural Bridge, is a spectacular
example of dissolution. The
carbonate rocks that make up the
bridge have been dissolved away by
groundwater and surface water,
leaving the bridge

Hydrolysis
• In hydrolysis, elements in water
(hydrogen and oxygen) replace
elements in the original material,
creating a new substance.
Granite gneiss is converting to
clay by hydrolysis
This deeply weathered granite gneiss
has been weathered by hydrolysis.

Oxidation
• In oxidation, oxygen
reacts with the original
material to create new
material. Iron minerals
are especially likely to
be oxidized.
• Oxidation is
characterized by red,
orange, and yellow
stains that look like
rust. These Highland
County shales show
evidence of oxidation.

 The action of plants and
animals leads to breaking of
rocks.
 Roots causing disintegration
of rocks.
 The roots of the trees
penetrate into the cracks of
the rocks.

 Burrowing
animals
 Quarrying
 By human
excreta

Climate and Weathering
Climate has an important effect on
weathering. The same rock in a
different climate weathers very
differently.
Humid and Warm
• In humid and warm
regions, chemical weathering is
the dominant type of
weathering. Landforms tend to be
more rounded and soils tend to be
thicker. Virginia has a warm, humid
climate.
Old Rag Mountain, is typical of
landforms in humid areas. Note the
gentle, rounded slopes and
abundance of vegetation.

Dry and Cold
• In dry and cold regions, physical
weathering is the dominant type of
weathering. Landforms tend to be
sharp and angular and soils tend to
be thin.
Sharp, angular landforms such as
these are typical of landforms in
desert regions.

Soil Development
Soils result from weathering of
rocks. Soils can be grouped
according to their origins: residual
soil, colluvial soil, and alluvial soil.
Residual Soil
• Residual soil is soil formed from
the weathering of the bedrock
below. The texture and
composition of residual soil
reflects the parent rock.
Residual soil forms on the bedro
This deeply weathered residual soil
(above photo) formed on mafic
igneous rocks. Erosion by running
water causes the “badlands”
topography.

Colluvial Soil
• Colluvial soil is soil formed
from the weathering of
bedrock and then moved
downslope by
gravity. Colluvial soil is often
different from the bedrock
below it.
Colluvial soils form on hillsides from
material that has moved down the
slope
This colluvial soil (above photo)
formed on a steep Note the large,
angular blocks of parent rock.

Alluvial Soil
• Alluvial soil is soil
formed on stream
deposits. It is nearly
always different from
the bedrock below it.
Alluvial soils are made up of grains
that have been transported and
deposited by stream processes.

Landforms of Weathering
• Regolith and Soil
Most landforms to some extent show the effects of weathering. On
the bedrock surface of these landscapes are the accumulations of
the products of weathering. Within these accumulations are
materials displaying various degrees of physical, chemical, and
biological alteration. These materials range in size from large
boulders to clay sized particles less than 0.004 millimeters in
diameter. Geomorphologists refer to these accumulations
as regolith. Regolith can be further altered by climate, organisms,
and topography over time to create soil. Soil is the most obvious
landform of weathering.

 Limestone Landforms
Among the most interesting and most beautiful landforms of weathering are those
which develop in regions of limestone bedrock. These landscapes are commonly
called karst. In karst landscapes weathering is concentrated along joints and bedding
planes of the limestone producing a number of different sculptured features from the
effects of solution. Depressions of all sizes and shapes pit the landscape surface and
are the most obvious features associated with karst. Beneath the surface, solution
results in the formation of caves, springs, underground water channels, and deposits
from evaporation.
 Periglacial Landforms
Unique weathering landforms are also found in polar and sub-polar regions. In these
regions, physical weathering processes are dominant, with active freeze-thaw and
frost-shattering being the most active. Associated with these weathering processes
are a number of unique surface features that develop only
in periglacial environments. Collectively known as patterned ground, these surface
features resemble circles, polygons, nets, steps, and stripes. The outlines of all of
these features consist of elevated accumulations of coarse regolith fragments.
Scientists believe that these outlines result from the systematic sorting of particles of
a wide range of texture sizes by freeze-thaw action. The sorting causes larger
fragments to move vertically upward and horizontally outward. Horizontal
movement stops when one feature encounters another, linking the perimeter of two
or more features. The linking of many adjacent features creates net-like patterns.

Engineering importance of rock weathering:
As engineer is directly or indirectly interested in rock weathering specially when
he has to select a suitable quarry for the extraction of stones for structural and
decorative purposes. The process of weathering always causes a lose in the
strength of the rocks or soil.
For the construction engineer it is always necessary to see that:
To what extent the area under consideration for a proposed project has been
affected by weathering and
What may be possible effects of weathering processes typical of the area on the
construction materials.

Earth structure and
composition

EARTH’S INTERNALSTRUCTUREANDCOMPOSITION
The Earth is divided into three distinct layers. They are Crust, Mantle and Core. The Earth is
about 6378 km in radius.

CRUST
The outermost layer of the Earth is called the crust. It composes about 1/2%
(0.005) of the Earth's total mass. The Crust is subdivided into Oceanic and
Continental crusts.
The Oceanic crust is the layer below the deep ocean basins. It is basaltic,
made up predominantly of the rock basalt, dense (density > = 3.0 to 3.2
g/cm3), thin (10-15 km) and young (<< 250My).
The Continental crust is the layer that forms the continents. It is granitic,
made up predominantly of the rock granite, plus overlying sediments), light
(density = 2.7 g/cm3), thick (40-60km) and old (250 - 3700 My).

MOHODISCONTINUITY
• The lower boundary of the crust, both
oceanic and continental, is a seismic
discontinuity (reflector) called the
Moho.
• LITHOSPHERE
• The crust (both oceanic and
continental) together with the
uppermost mantle behave as rigid,
brittle, rocky plates and together form
the lithosphere. The lithosphere is
generally considered to be the upper
100 km of the Earth.
• Note that the lithosphere includes the
crust, but also includes part of the
upper mantle.

• MANTLE
• The region between the Moho (base of the
crust) and the top of the liquid metal core at
2900 km depth is the mantle.
• The mantle is subdivided into Upper
Mantle, Lower Mantle and Transition zone.
It composes 67% of the mass of the planet.
The mantle is solid silicate (rock).
• Convection in the solid mantle is believed
responsible for motion of the surface plates.
This convection is driven by radioactive
decay of the naturally radioactive elements,
U (uranium), Th (thorium), and K
(potassium). Within the solid silicate
mantle, there is a prominent seismic
discontinuity (reflector) at about 660 km
depth and a less prominent discontinuity at
400 km depth. These are believed to be due
to changes in the crystal structure of the
silicate material in response to the
increased pressure.

GUTENBERG DISCONTINUITY
Gutenberg discontinuity separates mantle
from core, where change from silicates and
oxides to a molten iron, nickel, silicon,
phosphorous liquid.
CORE
The core is the region below the mantle
(2900-6370 km depth). The core is
subdivided into the outer liquid core and the
inner solid core. It is made of metal, [Fe
(iron), Ni (nickel), plus a small amount of a
lighter element, probably Si. The outer core
is liquid (molten) down to a depth of 5200
km below the surface, and is solid metal
below.
Convection in the metal core is believed
responsible for the magnetic field.

INTERNAL STRUCTURE OF EARTH
• Layers of the Earth
• To understand the details of plate tectonics, one must first
understand the layers of the Earth. Unfortunately, humankind
has insufficient first-hand information regarding what is
below; most of what we know is pieced together from
models, seismic waves, and assumptions based on meteorite
material. The Earth can be divided into layers based on
chemical composition and physical characteristics.

• Chemical Layers
The Earth has three main divisions based on its chemical
composition, chemical makeup. Indeed, there are countless
variations in composition throughout the Earth, but only two
significant changes occur, leading to three distinct chemical
layers.

• Crust
• The crust is the outermost chemical layer, and the layer humans
currently reside on. The crust has two types: continental crust,
which is relatively low density and has a composition similar to
granite, and oceanic crust, which is relatively high density (especially
when it is cold and old) and has a composition similar to basalt. In
the lower part of the crust, rocks start to be more ductile and less
brittle because of added heat. Earthquakes, therefore, generally
occur in the upper crust.
• At the base of the crust is a substantial change in seismic velocity
called the Mohorovičić Discontinuity, or Moho for short, discovered
by Andrija Mohorovičić (pronounced mo-ho-ro-vee-cheech) in 1909
by studying earthquake wave paths in his native Croatia. It is caused
by the dramatic change in composition between the mantle and the
crust. Underneath the oceans, the Moho is about 5 km down. Under
continents, the average is about 30-40 km, except near a sizeable
mountain-building event, known as an orogeny, where that
thickness is roughly doubled.

• Mantle
• The mantle is the layer below the crust and above the core. It
is the most substantial layer by volume, extending from the
base of the crust to a depth of about 2900 km. Most of what
we know about the mantle comes from seismic waves, though
some direct information can be gathered from parts of the
ocean floor brought to the surface, known as ophiolites. Also
carried within magma are xenoliths, small chunks of lower
rock carried to the surface by eruptions. These xenoliths are
made of the rock peridotite, which is ultramafic on the scale
of igneous rocks. We assume the majority of the mantle is
made of peridotite.

• Core
• The core of the Earth, which has both liquid and solid
components, is made mainly of iron, nickel, and oxygen. It was
first discovered in 1906 by looking into seismic data. It took
the union of modeling, astronomical insight, and seismic data
to arrive at the idea that the core is primarily metallic iron.
Meteorites contain much more iron than typical surface rocks.
If meteoric material is what made the Earth, the core would
have formed as dense material (including iron and nickel) sank
to the center of the Earth via its weight as the planet formed,
heating the Earth intensely.

• Physical Layers
• The Earth can also be broken down into five distinct physical
layers based on how each layer responds to stress. While
there is some overlap in the chemical and physical
designations of layers, precisely the core-mantle boundary,
there are significant differences between the two systems. (2
Plate Tectonics – An Introduction to Geology, n.d.)

• Lithosphere
• The lithosphere, with ‘litho’ meaning rock, is the outermost
physical layer of the Earth. Including the crust, it has both
oceanic and continental components. Oceanic lithosphere,
ranging from a thickness of zero (at the forming of new plates
on the mid-ocean ridge) to 140 km, is thin and rigid. The
continental lithosphere is more plastic (especially with depth)
and thicker, from 40 to 280 km thick. Most importantly, the
lithosphere is not continuous. Instead, it is broken into several
segments that geologists call plates. A plate boundary is
where two plates meet and move relative to each other. It is
at and near plate boundaries where plate tectonics are seen,
including mountain building, earthquakes, and volcanism.

• Asthenosphere
• With ‘astheno’ meaning weak, the asthenosphere is the layer
below the lithosphere. The most distinctive property of the
asthenosphere is movement. While still solid, over geologic
time scales, it will flow and move because it is mechanically
weak. In this layer, partly driven by convection of intense
interior heat, movement allows the lithospheric plates to
move. Since certain types of seismic waves pass through the
asthenosphere, we know that it is solid, at least at the short
time scales of the passage of seismic waves. The depth and
occurrence of the asthenosphere are dependent on heat and
can be very shallow at mid-ocean ridges and very deep in
plate interiors and beneath mountains.

• Mesosphere
• The mesosphere, or lower mantle as it is sometimes called, is more
rigid and immobile than the asthenosphere, though still hot. This
can be attributed to increased pressure with depth. Between
approximately 410 and 660 km depth, the mantle is in a state of
transition, as minerals with the same composition are changed to
various forms, dictated by increasing pressure conditions. Changes
in seismic velocity show this, and this zone also can be a physical
barrier to movement. Below this zone, the mantle is uniform and
homogeneous, as no significant changes occur until the core is
reached.

The outer core is the only liquid layer found within Earth. It starts at 2,890 km (1,795
mi) depth and extends to 5,150 km (3,200 mi). Inge Lehmann, a Danish geophysicist,
in 1936, was the first to prove that there was an inner core that was solid within the
liquid outer core based on analyzing seismic data. The solid inner core is about 1,220
km (758 mi) thick, and the outer core is about 2,300 km (1,429 mi) thick.
It seems like a contradiction that the hottest part of the Earth is substantial, as
hot temperatures usually lead to melting or boiling. The solid inner core can be
explained by understanding that the immense pressure inhibits melting, though as
the Earth cools by heat flowing outward, the inner core grows over time. As the
liquid iron and nickel in the outer core moves and convects, it becomes the most
likely source for Earth’s magnetic field. This is critically important to maintaining the
atmosphere and conditions on Earth that make it favorable to life. Loss of outer core
convection and the Earth’s magnetic field could strip the atmosphere of most of the
gases essential to life and dry out the planet, much like what has happened to Mars.

Structure of Earth’s Crust
The fundamental unifying principle of geology and the rock cycle is the theory of Plate
Tectonics. Plate tectonics describes how the layers of the Earth move relative to each
other. Specifically, the outer layer is divided into tectonic or lithospheric plates. As the
tectonic plates float on a mobile layer beneath called the asthenosphere, they collide,
slide past each other, and split apart. As a result, significant landforms are created at
these plate boundaries, and rocks making up the tectonic plates move through the rock
cycle.

Continents
The oldest continental rocks are billions of years old, so the continents have
had much time to happen to them. Constructive forces cause physical
features on Earth’s surface known as landforms to grow. Crustal
deformation – when crust compresses, pulls apart, or slides past other
crust – results in hills, valleys, and other landforms. Mountains rise when
continents collide when one slab of ocean crust plunges beneath another
or a slab of continental crust to create a chain of volcanoes. Sediments are
deposited to form landforms, such as deltas. Volcanic eruptions can also be
destructive forces that blow landforms apart. The destructive forces of
weathering and erosion modify landforms. Water, wind, ice, and gravity are
fundamental forces of erosion.

Oceanic Basins
The ocean basins are all younger than 180 million years. Although the
ocean basins begin where the ocean meets the land, the continent extends
downward to the seafloor, making the continental margin of continental
crust.
The ocean floor itself is not flat. The most distinctive feature is the
mountain range that runs through much of the ocean basin, known as the
mid-ocean ridge. The ocean trenches are the deepest places of the ocean,
many of which are found around the edge of the Pacific Ocean. Chains of
volcanoes are also found in the center of the oceans, such as around
Hawaii. Finally, flat plains are located on the ocean floor with their features
covered by mud.

Evidencesinsupportofcontinentaldrift
• The evidences that support the hypothesis of continental drift
include the fit of the shorelines of continents,
• the appearance of the same rock sequences and mountain
ranges of the same age on continents now widely separated,
the matching of the glacial deposits and palaeoclimatic zones,
• and the similarities of many extinct plant and animal groups
whose fossil remains are found today on widely separated
continents.

• In geologic terms, a plate is a large, rigid slab of solid rock.
The word tectonics comes from the Greek root "to build."
The term plate tectonics refers to how the Earth's surface is
built of plates.
• The theory of plate tectonics states that the Earth's
outermost layer is fragmented into a dozen or more large
and small plates that are moving relative to one other as
they ride atop hotter, more mobile material.
• Plate tectonics :- The theory of plate tectonics states that
the Earth's lithosphere consists of large, rigid plates that
move horizontally in response to the flow of the
asthenosphere beneath them, and that interactions among
the plates at their borders cause major geologic activity,
including the creation of oceans, continents, mountains,
volcanoes, and earthquakes.

• SEVEN LARGER AND SEVERAL SMALLER PLATES
• The largest plates include the Pacific plate, the North American plate, the
south American plate, the Eurasian plate, the Antarctic plate, and the
African plate, the European plate
• The Pacific plate is the largest plate at nearly 14,000 km wide.
• Smaller plates include the Cocos plate, the Nazca plate, the Caribbean plate,
and the Gorda plate.
• The Cocos plate is 2000 km wide.

wind
 Wind as a Geological Agent

 Effective in performing geologic work under certain circumstances.

 Most effective when loose, dry and fined grained sediment, is
exposed at the ground surface.

 Particles larger than fine sand, are normally too big to be picked up
and transported by the wind’s energy.

 Wet sedimentary particles - tend to bind together, inhibiting the
lifting potential of the wind.

 Most effective in arid and semiarid regions.


Ventifacts are any bedrock surface or stone that has been abraded or shaped by wind-
blown sediment in a process similar to sand blasting.
Wind-abraded rocks are called dreikanters from a South African
word meaning "three corners."

STREAM :- any body of flowing water confined within a channel, regardless of size.
Flows down hill through local (TOPOGRAPHIC LOWS)
DRAINAGE BASIN :- The region from which a stream draws water is its drainage
basin.
SIZE OF A STREAM AT ANY POINT
is related in part to the size (area) of the drainage basin upstream from that point.
Its size is influenced by
CLIMATE – amount of precipitation and evaporation
VEGETATION – lack of it and
UNDERLYING GEOLOGY

Work of rivers
 STREAM :- any body of flowing water confined within a channel,
regardless of size.
 Flows down hill through local (TOPOGRAPHIC LOWS)

 DRAINAGE BASIN :- The region from which a stream draws water is
its drainage basin.

 SIZE OF A STREAM AT ANY POINT

 is related in part to the size (area) of the drainage basin upstream
from that point.
 Its size is influenced by
 CLIMATE – amount of precipitation and evaporation
 VEGETATION – lack of it and
 UNDERLYING GEOLOGY

Amountofsedimentsettledathebottomoftherivercourse

•
• LOAD :- The total quantity of material that a stream transports.
• Bed load
• Dissolved load
• Suspended load - saltation
• BED LOAD
• Heavier debris – rolled or pushed along the bottom of the stream bed.
• SUSPENDED LOAD (Muddy appearance to stream water)
• Material that is light or fine enough to be moved along suspended in the stream,
supported by the flowing water.
• SALTATION
• Intermediate sized material carried in short hops along the stream bed by
saltation process.
• DISSOLVED LOAD
• Substances – completely dissolved in the water.
•

• Marine abrasion involves the rubbing and grinding
action of the sea water on the rocks of the shore
• Sand particles and other small fragments that are
hurled up again and again .
• Continued marine erosion results in considerable or
even total modification of the original shore line
• The strength of the sea waves, currents and their
magnitude.
• The lithology
• The sea ward slope
• The height of the shore line
• The depth and chemical composition of the water
• The original profile of the shore line

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1. EARTHQUAKE
It is vibration of the Earth's by shock waves generated by
energy released from rocks rupturing under stress
Causes of earthquakes: Faults, landslides, rockslides, movement of magma or
gases, volcanic activities among others
Focus: Exact location of the earthquake
below the surface of the Earth
Epicenter: The position on the surface
of the Earth directly above the focus
Seismic waves: waves which travel
within the Earth
P (primary) wave - moves
in a straight line path with
alternating compression and
expansion
S (secondary) wave - moves
in a sinusoidal motion along
its path of movement

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P-Wave Propagation
Compressional waves
Series of contractions and relaxations
Fastest, ~5 km/sec (depends on rock type)
Travel through solid, liquid and gas
S-Wave Propagation
Shear waves: motion is right angles to
direction of wave
Half speed of P waves
Travel only through solid

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Seismographs is the machine that detects seismic waves.

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Modified MercalliScale
Measuresearthquakeintensity.
Describesdamagetostructures.ItrangesfromI(feltbyonlya
few)toXII(totaldestruction).
RichterScale
Measuresearthquakemagnitude.
Determinedbymeasuringtheamplitudeofthelargestwaveson
theseismogram. Itislogarithmicscale,whereeachnumberon
theRichterScaleistentimesgreaterinwaveamplitude(each
numberontheRichterScaleinvolvesanenergyreleaseabout32
timesasgreat).
Measuring Earthquakes
Several different scales exist to measure earthquakes

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Locations of Earthquakes
Mostoccuralongtectonicplateboundaries

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Earthquake of different
magnitudes all the time

• AN EARTHQUAKE
• Is a trembling of the ground caused, by sudden release of energy in
underground rocks.
• Most earthquakes occur
• Where rocks are subjected to the stress associated with tectonic
plate movement – that is, near plate boundaries, under such stress,
rocks may deform elastically and accumulate STRAIN ENERGY, which
builds until the rocks either shift suddenly along preexisting faults or
rupture to create new faults, causing earthquakes.

EARTHQUAKE BELTS IN INDIA
Zone of maximum intensity (0.1-0.15)
 Assam, northern Bihar, strips of Uttar Pradesh,
Uttaranchal, U.P, Delhi, Haryana, Punjab, Himachal
Pradesh, Jammu & Kashmir.
Intermediate intensity (0.05)
 Southern flat lands of Haryana Punjab, U.P,
Rajasthan, M.P Bihar Bengal ,Orrissa, Gujarat, and
Maharashtra
Minimum intensity (0.01)
 The triangular parts of India surrounded on the sides
of Arabian sea, bay of Bengal and the Indian ocean.

• Groundwater: water found underground, in the pore
spaces of earth materials
• * It moves: it’s a liquid, so it flows (slowly) from high
elevations toward low areas
* Rivers like it: many rivers and streams are fed by
groundwater from below. In arid regions, river water leaks
out and down into the groundwater.
• * People like it: ~ 40% of our water resources are
groundwater supplies


A Few Definitions:
* Groundwater: underground water found saturating (filling) the pores of
earth materials. * Usually refers to fresh water: saline groundwater is
called “brine”, and is usually found deeper.

* Zone of Aeration: above the water table, pores are only partially filled;
water plus air

* Zone of Saturation: below water table, pores filled with groundwater

* Water table: boundary between unsaturated and saturated zones

* Perched water table: a shallow, local water table located above the
regional water table.
 Porosity: Informal: holes in the rock where the water stays
* Formal: ratio of pore space to total volume in rock or sediment
(expressed as %)
the more porous a material is, the more water it can hold
* Limestones: 1-20%
* Sandstones: 5-25%
* Shales: 20-45%

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