Introduction to Geology

(in Greek, Geo means Earth, Logos means Science) is a branch of science dealing with the study of the
Earth. It is also known as earth 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.

BRANCHES OF GEOLOGY:

• Physical geology -
is the study of the earth's rocks, minerals, and soils and how they have forme through time.
• Petrology -
scientific study of rocks that deals with their composition, texture, and structure.
• Mineralogy -
scientific discipline that is concerned with all aspects of minerals, including their physical properties,
chemical composition, internal crystal structure, and occurrence and distribution in nature.
• Crystallography -
Is the science that examines the arrangement of atoms in solids.
• Stratigraphy -
is the study of layered materials (strata) that were deposited over time.
• Paleontology -
Is the study of the history of life on Earth as based on fossils.
• Hydrology -
Is the science that encompasses the study of water on the Earth's surface and beneath the surface of the Earth.

Elementary knowledge on Continental Drift and Plate Tectonics

Plate: The Earth’s crust consists of a number of mobile plates, masses of crust that move independently of
adjacent plates.

Tectonics: From ancient Greek Tektonikos meaning ‘Pertaining to building”. Dealing with structural features
of the Earth.

PLATE TECTONICS
AKA: Lithospheric plate. The process that involves the interaction of moving crustal plates and results in
major structural features of the Earth.

2 TYPES OF LAYER

COMPOSITIONAL- The compositional layer is defined by the chemical composition of the layers and the
physical layer is defined by the layers’ physical properties (solid, liquid, or how waves move through the
layer).

Layer Definition Depth

Crust The outermost solid layer of a rocky planet or natural 0-100km

satellite. Chemically distinct from the underlying mantle. silicates

Mantle A layer of the Earth (or any planet large enough to support 100-2900km
internal stratification) between the crust and the outer core. iron and
It is chemically distinct from the crust and the outer core. magnesium
The mantle is not liquid. It is, however, ductile, or plastic, silicates
which means that on very long time scales and under
pressure it can flow. The mantle is mainly composed of
aluminum and silicates.

Core The innermost layers of the Earth. The Earth has an outer 2900-6370km
core (liquid) and an inner core (solid). They are not metals
chemically distinct from each other, but they are chemically
distinct from the mantle. The core is mainly composed of
nickel and iron.

MECHANICAL LAYER-

The mechanical layers of the Earth a differentiated by their strength or rigidity. These layers are not the same
as the compositional layers of the Earth, such as the crust, mantle, and core, though sometimes the
boundaries fall in the same places.

Information about the mechanical layers

Layer Definition Depth

Lithosphere The outermost and most rigid mechanical layer of the 0-100 km
Earth. The lithosphere includes the crust and the top
of the mantle. The average thickness is ~70km, but
ranges widely: It can be very thin, only a few km thick
under oceanic crust or mid-ocean ridges, or very
thick, 150+ km under continental crust, particularly
mountain belts.

Asthenosphere The asthenosphere is underneath the lithosphere. It 100-350 km

is about 100km thick, and is a region of the mantle Soft plastic
that flows relatively easily. Reminder: it is not liquid. *note: The
 Information about the mechanical layers

Layer Definition Depth

mantle is not
liquid!

Mesosphere The mesosphere is beneath the asthenosphere. It 350-2900km

encompasses the lower mantle, where material still stiff plastic
flows but at a much slower rate than the
asthenosphere.

Outer Core A layer of liquid iron and nickel (and other elements)
beneath the mesosphere. This is the only layer of the
Earth that is a true liquid, and the core-mantle
boundary is the only boundary of Earth’s layers that
is both mechanical and compositional. Flow of the
liquid outer core is responsible for Earth’s magnetic
field.

Types of Plate Boundaries

Plate boundaries can be categorized in three fundamental types:
(a) Divergent boundaries, where plates separate and move in opposite directions, allowing new
lithosphere to form from upwelling magma. This either occurs at mid-ocean ridges (the so-called
seafloor spreading) or at rifted continental margins;

(b) Convergent boundaries, where plates move towards each other. One plate either sinks beneath the
other along a subduction zone or plates collide because neither can be subducted; and

(c) Transform fault boundaries, where plates move horizontally past each other.
Based on the three types of plate boundaries, a global network of approximately twelve major plates of
irregular shape and size cover the Earth's crust. Where one type of plate boundary is terminated it is
transformed into a boundary of a different type.
>Volcanoes and mountain form as a result of convergent boundaries collide.

>Earthquakes and tsunami occur at convergent and transform boundaries.

>Fissures, cracks and rift in the surface occur at divergent boundaries .

>Seafloor spreading and Volcanoes occur at divergent boundaries on the ocean floor.

CONTINENTAL DRIFTS

-is the theory that the earth’s continent has moved over geologic time relative to each other, thus appearing to
have “drifted” across the ocean bed.

Alfred Wegener became the “father of continental drift” by amassing considerable supporting evidence that
the continents moved over time.
Born: Germany, 1880
PhD: Astronomy
Profession: Meteorologist and Greenland Explorer.
Died: 1930

In 1915 Wegener published his work in The Origin of the Continents and Oceans.

The theory of continental drift

Wegener thought all the continents were once joined together in an "Urkontinent" before breaking up and
drifting to their current positions. But geologists soundly denounced Wegener's theory of continental drift
after he published the details in a 1915 book called "The Origin of Continents and Oceans." Part of the
opposition was because Wegener didn't have a good model to explain how the continents moved apart.
Though most of Wegener's observations about fossils and rocks were correct, he was outlandishly wrong on a
couple of key points. For instance, Wegener thought the continents might have plowed through the ocean
crust like icebreakers smashing through ice.
"There's an irony that the key objection to continent drift was that there is no mechanism, and plate tectonics
was accepted without a mechanism," to move the continents, said Henry Frankel, an emeritus professor at the
University of Missouri-Kansas City and author of the four volume "The Continental Drift Controversy"
(Cambridge University Press, 2012).
Although Wegener's "continental drift" theory was discarded, it did introduce the idea of moving continents
to geoscience. And decades later, scientists would confirm some of Wegener's ideas, such as the past
existence of a supercontinent joining all the world's landmasses as one. Pangaea was a supercontinent that
formed roughly 200 to 250 million years ago, according to the U.S. Geological Survey (USGS) and was
responsible for the fossil and rock clues that led Wegener to his theory.

ALFRED WEGENER’S CONTINENTAL DRIFTS EVIDENCES

Evidence
Alfred Wegener collected diverse pieces of evidence to support his theory, including geological “fit” and fossil
evidence. It is important to know that the following specific fossil evidence was not brought up by Wegener to
support his theory. Wegener himself did not collect the fossils but he called attention to the idea of using
these scientific doc uments stating there were fossils of species present in separate continents in order to
support his claim.

Illustration showing similar rock assemblages across different continents.

Geological “fit” evidence is the matching of large-scale geological features on different continents. It has been
noted that the coastlines of South America and West Africa seem to match up, however more particularly the
terrains of separate continents conform as well. Examples include: the Appalachian Mountains of eastern
North America linked with the Scottish Highlands, the familiar rock strata of the Karroo system of South
Africa matched correctly with the Santa Catarina system in Brazil, and the Brazil and Ghana mountain ranges
agreeing over the Atlantic Ocean.

Another important piece of evidence in the Continental Drift theory is the fossil relevance. There are various
examples of fossils found on separate continents and in no other regions. This indicates that these continents
had to be once joined together because the extensive oceans between these land masses act as a type of
barrier for fossil transfer. Four fossil examples include: the Mesosaurus, Cynognathus, Lystrosaurus, and
Glossopteris.
Modern day representation of the Mesosaurus.
The Mesosaurus is known to have been a type of reptile, similar to the modern crocodile, which propelled
itself through water with its long hind legs and limber tail. It lived during the early Permian period (286 to
258 million years ago) and its remains are found solely in South Africa and Eastern South America. Now if the
continents were in still their present positions, there is no possibility that the Mesosaurus would have the
capability to swim across such a large body of ocean as the Atlantic because it was a coastal animal.

Modern day representation of the Cynognathus.

The now extinct Cynognathus, which translates to “dog jaw”, was a mammal- like reptile. Roaming the
terrains during the Triassic period (250 to 240 million years ago), the Cynognathus was as large as a modern
wolf. Its fossils are found only in South Africa and South America. As a land dominant species, the
Cynognathus would not have been capable of migrating across the Atlantic.

Modern day representation of the Lystrosaurus.

The Lystrosaurus, which translates to “shovel reptile,” is thought to have been an herbivore with a stout build
like a pig. It is approximated that it grew up to one meter in length and was relatively dominant on land
during the early Triassic period (250 million years ago). Lystrosaurus fossils are only found in Antarctica,
India, and South Africa. Similar to the land dwelling Cynognathus, the Lystrosaurus would have not had the
swimming capability to traverse any ocean.

Modern day representation of the Glossopteris.

Possibly the most important fossil evidence found is the plant, Glossopteris. Known as a woody, seed bearing
tree, the Glossopteris is named after the Greek description for tongue due to its tongue shaped leaves and is
the largest genus of the extinct descendant of seed ferns. Reaching as tall as 30 meters, the Glossopteris
emerged during the early Permian period (299 million years ago) and became the dominant land plant
species until the end of the Permian. The Glossopteris fossil is found in Australia, Antarctica, India, South
Africa, and South America—all the southern continents. Now, the Glossopteris seed is known to be large and
bulky and therefore could not have drifted or flown across the oceans to a separate continent. Therefore, the
continents must have been joined at least one point in time in order to maintain the Glossopteris’ wide range
across the southern continents.

Description showing the fossil locations of the Mesosaurus, Cynognathus, Lystrosaurus, and Glossopteris
spread across different continents.
If the continents of the Southern Hemisphere are put together, the distribution of these four fossil types form
continuous patterns across continental boundaries. Of course, possible explanations are brought to attention.
One explanation is the species could have migrated via a land bridge or swam to the other continents.
However, a land bridge is not applicable due to the differences in densities between the continents and
oceans floor and violation of the isostasy concept. Moreover, swimming as a possibility is foolish due to the
lack of formidable swimming capabilities to travel across such an extensive body of water like the Atlantic. An
additional resolution is that the species could have merely evolved separately on the other continents.
Undoubtedly, this interpretation is in complete disagreement with Darwin’s evolution theory.

Wegener’s Conclusions:

• That the continents were once joined. Therefore, they must have moved apart over time.
• Contracting Earth theory was not consistent with the facts.

References:

https://www.britannica.com/biography/Alfred-Wegener

https://www.google.com/amp/s/www.livescience.com/amp/37706-what-is-plate-tectonics.html

https://pubs.usgs.gov/gip/dynamic/tectonic.html

www.nationalgeographic.org/encyclopedia

https://courses.lumenlearning.com/geophysical/chapter/theory-of-continental-drift/

http://publish.illinois.edu/alfredwegener/evidence/

https://www.geolsoc.org.uk/Plate-Tectonics/Chap1-Pioneers-of-Plate-Tectonics/Alfred-
Wegener/Fossil-Evidence-from-the-Southern-Hemisphere
The Composition and Structure of the Earth

Core, mantle, and crust are divisions based on composition. The crust makes up less than 1 percent of Earth by
mass, consisting of oceanic crust and continental crust is often more felsic rock. The mantle is hot and
represents about 68 percent of Earth’s mass. Finally, the core is mostly iron metal. The core makes up about
31% of the Earth. Lithosphere and asthenosphere are divisions based on mechanical properties.
The lithosphere is composed of both the crust and the portion of the upper mantle that behaves as a brittle,
rigid solid. The asthenosphere is partially molten upper mantle material that behaves plastically and can flow.

Crust and Lithosphere

Earth’s outer surface is its crust; a cold, thin, brittle outer shell made of rock. The crust is very thin, relative to
the radius of the planet. There are two very different types of crust, each with its own distinctive physical and
chemical properties. Oceanic crust is composed of magma that erupts on the seafloor to create basalt lava
flows or cools deeper down to create the intrusive igneous rock gabbro. Sediments, primarily muds and the
shells of tiny sea creatures, coat the seafloor. Sediment is thickest near the shore where it comes off the
continents in rivers and on wind currents. Continental crust is made up of many different types of igneous,
metamorphic, and sedimentary rocks. The average composition is granite, which is much less dense than the
mafic igneous rocks of the oceanic crust. Because it is thick and has relatively low density, continental crust
rises higher on the mantle than oceanic crust, which sinks into the mantle to form basins. When filled with
water, these basins form the planet’s oceans. The lithosphere is the outermost mechanical layer, which behaves
as a brittle, rigid solid. The lithosphere is about 100 kilometers thick. The definition of the lithosphere is based
on how earth materials behave, so it includes the crust and the uppermost mantle, which are both brittle. Since
it is rigid and brittle, when stresses act on the lithosphere, it breaks. This is what we experience as an
earthquake.

Mantle

The two most important things about the mantle are: (1) it is made of solid rock, and (2) it is hot. Scientists
know that the mantle is made of rock based on evidence from seismic waves, heat flow, and meteorites. The
properties fit the ultramafic rock peridotite, which is made of the iron- and magnesium-rich silicate minerals.
Peridotite is rarely found at Earth’s surface. Scientists know that the mantle is extremely hot because of the
heat flowing outward from it and because of its physical properties. Heat flows in two different ways within
the Earth: conduction and convection. Conduction is defined as the heat transfer that occurs through rapid
collisions of atoms, which can only happen if the material is solid. Heat flows from warmer to cooler places until
all are the same temperature. The mantle is hot mostly because of heat conducted from the core. Convection is
the process of a material that can move and flow may develop convection currents. Convection in the mantle is
the same as convection in a pot of water on a stove. Convection currents within Earth’s mantle form as material
near the core heats up. As the core heats the bottom layer of mantle material, particles move more rapidly,
decreasing its density and causing it to rise. The rising material begins the convection current. When the warm
material reaches the surface, it spreads horizontally. The material cools because it is no longer near the core. It
eventually becomes cool and dense enough to sink back down into the mantle. At the bottom of the mantle, the
material travels horizontally and is heated by the core. It reaches the location where warm mantle material
rises, and the mantle convection cell is complete.

Core

At the planet’s center lies a dense metallic core. Scientists know that the core is metal for a few reasons. The
density of Earth’s surface layers is much less than the overall density of the planet, as calculated from the
planet’s rotation. If the surface layers are less dense than average, then the interior must be denser than average.
Calculations indicate that the core is about 85 percent iron metal with nickel metal making up much of the
remaining 15 percent. Also, metallic meteorites are thought to be representative of the core. If Earth’s core
were not metal, the planet would not have a magnetic field. Metals such as iron are magnetic, but rock, which
makes up the mantle and crust, is not. Scientists know that the outer core is liquid and the inner core is solid
because S-waves stop at the inner core. The strong magnetic field is caused by convection in the liquid outer
core. Convection currents in the outer core are due to heat from the even hotter inner core. The heat that keeps
the outer core from solidifying is produced by the breakdown of radioactive elements in the inner core.

SUMMARY

1. DIVISIONS BASED ON COMPOSITION

CRUST

▪ A cold, thin, brittle outer shell made of rock

▪ The crust is very thin, relative to the radius of the planet

▪ The crust makes up less than 1 percent of Earth by mass, consisting of oceanic crust and continental
crust is often more felsic rock.
 ▪ There are two very different types of crust, each with its own distinctive physical and chemical
properties:

Oceanic crust

▪ composed of magma that erupts on the seafloor to create basalt lava flows or cools deeper down to
create the intrusive igneous rock gabbro.

Continental crust

▪ Made up of many different types of igneous, metamorphic, and sedimentary rocks.

▪ Continental crust rises higher on the mantle than oceanic crust, because it is thick and has relatively
low density

MANTLE

• A mantle is a layer inside a planetary body bounded below by a core and above by a crust.

• Mantles are made of rock or ices, and are generally the largest and most massive layer of the
planetary body.

• Mantles are characteristic of planetary bodies that have undergone differentiation by density.

• The mantle is hot and represents about 68 percent of Earth’s mass.

• A layer of silicate rock between the crust and the outer core.

• Its mass of 4.01 × 1024 kg is 67% the mass of the Earth.

• Thickness of 2,900 kilometers (1,800 mi) making up about 84% of Earth's volume.

• It is predominantly solid but in geological time it behaves as a viscous fluid.

• Partial melting of the mantle at mid-ocean ridges produces oceanic crust, and partial melting of the
mantle at subduction zone produces continental crust.

CORE

▪ core is mostly iron metal. The core makes up about 31% of the Earth.
▪ the innermost part of the earth, comprised of

a.) the inner core, at the center of the earth, made of iron; and

b) the outer core, which surrounds the inner core, made of iron and magma.

2. DIVISIONS BASED ON MECHANICAL PROPERTIES

 ▪ The lithosphere is composed of both the crust and the portion of the upper mantle that behaves as
a brittle, rigid solid.
▪ The asthenosphere is partially molten upper mantle material that behaves plastically and can
flow.

Earth Processes

Geological processes are dynamic processes at work in the earth's landforms and surfaces. The mechanisms
involved, weathering, erosion, and plate tectonics, combine processes that are in some respects destructive and
in others constructive.

Types of Earth Processes

Erosion

The movement of rock from one place to another.

is a natural process which is usually made by rock and soil being loosened from the earth's surface at one
location and moved to another. Erosion changes the landscape by wearing down mountains, filling in valleys,
and making rivers appear and disappear. It is usually a slow and gradual process that occurs over thousands
or millions of years. But erosion can be speeded up by such human activities as farming and mining. Erosion
begins with a process called weathering; in this process, environmental factors break rock and soil into smaller
pieces, and loosen them from the earth's surface.

Weathering

Weathering is the breaking up of surfaces by forces such as the air and water of the atmosphere.IBs the
breakdown of rocks at the Earth’s surface, by the action of rainwater, extremes of temperature, and biological
activity. It does not involve the removal of rock material.

Deposition
Some natural phenomena like wind and water are continuously applying their forces to the surface of Earth. As
a result, the Earth’s surface is eroded. Both of the natural phenomena particularly water transports this eroded
material to some other location on the Earth and deposit it there. This action of natural agents is called
deposition.

Plate Tectonics

Plate Tectonics is a theory scientists have about the earth's surface. Scientists think that the earth's outer
surface consists of 12 rigid plates. Some of these plates do not follow continental boundaries, and some include
both continents and oceans. They are all different shapes and sizes and are in continual motion. The plates
slowly slide on a soft plastic layer of molten rock called the mantle and move from 1.3 to 10 centimeters a year.
This tectonic activity occurs along the edges of the plates. When plates collide or push against each other, over
periods of millions of years, one plate will either slide on top of the other, which creates a fault movement
generating earthquakes and volcanoes, or crumples and forms mountains.

Weathering

is the breaking down or dissolving of rocks and minerals on Earths surface.

Types of Weathering:

Physical or Mechanical Weathering and Chemical Weathering.

Physical or Mechanical Weathering:

Physical weathering is the physical breakdown of rocks into smaller and smaller pieces without changing its
composition

Frost Wedging

is the process by which water seeps into cracks in a rock, expands on freezing, and thus enlarges the cracks.
The effectiveness of frost wedging is related to the frequency of freezing and thawing. In warm areas where
freezing is infrequent, in very cold areas where thawing is infrequent, or in very dry areas, where there is little
water to seep into cracks, the role of frost wedging is limited.

Thermal Stress

sometimes called insolation weathering,results from the expansion and contraction of rock, caused by
temperature changes. For example, heating of rocks by sunlight or fires can cause expansion of their constituent
minerals. As some minerals expand more than others, temperature changes set up differential stresses that
eventually cause the rock to crack apart

Abrasion

Rocks break down into smaller pieces through weathering. Rocks and sediment grinding against each other
wear away surfaces. This type of weathering is called abrasion, and it happens as wind and water rush over
rocks. The rocks become smoother as rough and jagged edges break off.

Root Wedging
Root Wedging is caused when a tree roots grow around a rock. The roots will work to get water and food for
the tree. Those roots will wedge through the rock forcing there way through causing the rock to split in half

Animals can also contribute to weathering. Animals can walk on rock or disturb it, causing landslides that
scrape or smooth rock surfaces. Burrowing animals such as badgers and moles can break up rock underground
or bring it to the surface, where it is exposed to other weathering forces

Chemical Weathering:

Chemical Weathering breakdown of rocks into smaller and smaller pieces by changing its composition

Oxidation

is the reaction of a substance with oxygen. This is the process that causes rust. When iron in rocks reacts with
oxygen, it forms iron oxide, which weakens the rock

Carbonation

it is the process of mixing water with carbon dioxide to make carbonic acid. This type of weathering is important
in making caves. Dissolved carbon dioxide in water or in moist air forms carbonic acid, and this acid reacts to
minerals in rocks

Hydrolysis
Is the chemical breakdown of a substance when combined with water. The most common example of hydrolysis
is feldspar, which can be found in granite changing to clay. When it rains, water seeps down into the ground and
comes in contact with granite rocks. The feldspar crystals within the granite react with the water and are
chemically altered to form clay minerals, which weaken the rock.

Acid Precipitation
Air pollution that results in more carbon dioxide and sulphur dioxide causes rain water to become even more
acidic. When moisture in the atmosphere dissolves these gases, they form acid rain. When acid rains fall on
rocks, the effects are even more than regular rainwater.
Lichens
There are things called lichens (combinations of fungi and algae) which live on rocks. Lichens slowly eat away
at the surface of rocks. The amount of biological activity that breaks down minerals depends on how much life
is in that area. You might find more activities like lichens near oceans where the air is humid and cooler.

WORK OF RIVERS

As rivers flow from highland to lowland they perform three important jobs, they erode, they transport the
material that they have eroded and then they deposit it. Small rivers flow down steep slopes and erode river
beds vertically downwards. Larger rivers flow down gentle slopes and erode banks laterally. Larger rivers
reaching the end of their journey flow over flat plains and deposit the material that they had eroded
upstream.

THREE FUNCTIONS OF RIVER:

1. Erosion
2. Transportation
3. Deposition

EROSION
The energy in a river causes erosion. The bed and banks can be eroded making it wider, deeper and longer.

Types of Erosion:
1. Vertical erosion makes a river channel deeper. This happens more in the upper stages of a river (the V of
vertical erosion should help you remember the V-shaped valleys that are created in the upper stages).

2. Lateral erosion makes a river wider. This occurs mostly in the middle and lower stages of a river.

Four main processes of erosion that occur in rivers:

1. Hydraulic action- The pressure of water breaks away rock particles from the river bed and banks. The
force of the water hits river banks and then pushes water into cracks. Air becomes compressed, pressure
increases and the riverbank may, in time collapse.
2. Abrasion - The sediment carried by a river scours the bed and banks. Where depressions exist in the
channel floor the river can cause pebbles to spin around and turn hollows into potholes.
3. Attrition- Eroded rocks collide and break into smaller fragments. The edges of these rocks become
smoother and more rounded. Attrition makes the particles of rock smaller. It does not erode the bed and bank.
Pieces of river sediment become smaller and more rounded as they move downstream.
4. Corrosion- Carbon dioxide dissolves in the river to form a weak acid. This dissolves rock by chemical
processes. This process is common where carbonate 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 been loosened by
erosion may be then transported along the river.

Four main processes of transportation:

1. Solution - minerals are dissolved in the water and carried along in solution. This typically occurs in areas
where the underlying bedrock is limestone.
2. Suspension - fine light material is carried along in the water.
3. Saltation - small pebbles and stones are bounced along the river bed.
4. Traction- large boulders and rocks are rolled along the river bed.

Deposition
Deposition is the process of the eroded material being dropped. This happens when a river loses energy. A
river can lose its energy when rainfall reduces, evaporation increases, friction close to river banks and shallow
areas which leads to the speed of the river reducing and therefore the energy reduces, when a river has to
slow down it reduces its speed (and ability to transport material) and when a river meets the sea.

Importance:

Rivers carry water and nutrients to areas all around the earth. They play a very important part in the water
cycle, acting as drainage channels for surface water. Rivers drain nearly 75% of the earth's land surface.

The works of seas and oceans and it’s importance

How do seas and oceans formed?

• The ocean formed from the escape of water vapor and other gases from the molten rocks of the
Earth to the atmosphere surrounding the cooling planet.
 • After the Earth's surface had cooled to a temperature below the boiling point of water, rain
began to fall—and continued to fall for centuries. As the water drained into the great hollows in
the Earth's surface, the primeval ocean came into existence. The forces of gravity prevented the
water from leaving the planet.

The geological works of seas and oceans

The coastal
erosion

Coastal erosion is the loss or displacement of land, or the long-term removal of sediment and rocks along
the coastline due to the action of waves, currents, tides, wind-driven water, waterborne ice, or other impacts
of storms. The landward retreat of the shoreline can measured and described over a temporal scale of tides,
seasons, and other short-term cyclic processes. Coastal erosion may be caused by hydraulic action, abrasion,
impact and corrosion by wind and water, and other forces, natural or unnatural.

Sea stacks

Erosion along rocky coasts occurs at various rates and is dependent both on the rock type and on the wave
energy at a particular site. As a result of the above-mentioned conditions, wave-cut platforms may be
incomplete, with erosional remnants on the horizontal wave-cut surface. These remnants are called sea stacks,
and they provide a spectacular type of coastal landform. Some are many metres high and form
isolated pinnacles on the otherwise smooth wave-cut surface. Because erosion is a continual process, these
features are not permanent and will eventually be eroded, leaving no trace of their existence.

Sea arches

Another spectacular type of erosional landform is the sea arch, which forms as the result of different rates of
erosion typically due to the varied resistance of bedrock. These archways may have an arcuate or rectangular
shape, with the opening extending below water level. The height of an arch can be up to tens of metres above
sea level.

Coastal deposition

• Coastal deposition is when the sea drops or deposits material. This can include sand, sediment and
shingle. This results in the formation of landforms of coastal deposition.

Sandbar
also called Offshore Bar, submerged or partly exposed ridge of sand or coarse sediment that is built by waves
offshore from a beach. The swirling turbulence of waves breaking off a beach excavates a trough in the sandy
bottom. Some of this sand is carried forward onto the beach and the rest is deposited on the offshore flank of
the trough.

PROSPECTING UNDER EARTHQUAKE

PROSPECTING is the first stage of the geological analysis, physical search for hydrocarbons, minerals fossils,
precious metals or minerals specimens and known as fossicking.

GEOPHYSICAL PROSPECTING is the study of the structure of the Earth’s crust by physical methods for the
location and surveying of minerals, it is an integral part of geophysics.

GEOPHYSICAL PROSPECTING TECHNIQUES:

1.) Seismic Method-the speeds of transmission of shock waves through the Earth.
2.) Gravity Method-involves measuring the gravitational attraction exerted by the earth at a measurement
station on the surface.
3.) Magnetic Method-to image anomalies in the earth's magnetic field caused by source bodies within the
sub-surface.
4.) Electrical Method-depends on the electrical or electrochemical properties of rocks.
5.) Radioactive Method-or radioactive dating as it is sometimes called, is a method used to date rocks and
other objects based on the known decay rate of radioactive isotopes.
6.) Well Logging Method-is the measurement of formation properties versus depth in a borehole.
7.) Electromagnetic Method-it use a low frequency time-varying magnetic field as a source to excite
electrical currents in the ground.

SEISMIC PROSPECTING

Prospecting based on the analysis of elastic waves generated in the earth by artificial means.

The elastic waves produced during sudden disturbance is called as Seismic waves. These waves are recorded
using the instrument Seismograph and the record obtain is Seismogram. It is important geophysical
prospecting applied in exploration of oil and natural gas deposits, deep ground water exploration, depth
estimation, geotechnical problems.

• Seismic prospecting can be done by two methods

 1.) Reflection Method is a method of exploration geophysics that uses the principles of seismology to
estimate the properties of the Earth's subsurface from reflected seismic waves.
2.) Refraction Method utilizes the refraction of seismic waves on geologic layers and rock/soil units in
order to characterize the subsurface geologic conditions and geologic structure.

TYPES OF SEISMIC WAVES

Seismic waves are classified into following:

Compressional or primary waves (P waves). This is the fastest kind of seismic wave, and, consequently, the
first to 'arrive' at a seismic station. Usually people can only feel the bump and rattle of these waves. P waves are
also known as compressional waves, because of the pushing and pulling they do. Motion of the particles in a
medium is parallel to direction of propagation of the wave. It has the highest velocity and is therefore the first
to be recorded. These waves can travel through any type of material, including fluids. It is formed from
alternating compressions and expansions.

Shear or Transverse or Secondary waves (S waves). The S wave travels only through solid material. With S
waves, the particle motion is transverse to the direction of travel and involves a shearing of the transmitting
rock. The motion of the particles in a medium is perpendicular to the direction of propagation of the wave. S
waves can travel only through solids, as fluids (liquids and gases) do not support shear stresses. S waves are
slower than P waves.

Surface waves (L waves). It is analogous to water waves and travel along the earth surface.

a.) Rayleigh waves

b.) Love waves

The motion of the particles in Rayleigh wave is in a vertical plane, but with reference to the direction of
propagation, the motion is elliptical.

In love wave the motion of the particle is horizontal and transverse to the direction of propagation.

Groundwater

What is groundwater?

Groundwater is fresh water (from rain or melting ice and snow) that soaks into the soil and is stored in the
tiny spaces (pores) between rocks and particles of soil. Groundwater accounts for nearly 95 percent of the
nation’s fresh water resources. It can stay underground for hundreds of thousands of years, or it can come to
the surface and help fill rivers, streams, lakes, ponds, and wetlands. Groundwater can also come to the surface
as a spring or be pumped from a well. Both of these are common ways we get groundwater to drink. About 50
percent of our municipal, domestic, and agricultural water supply is groundwater.

How does the ground store water?

Groundwater is stored in the tiny open spaces between rock and sand, soil, and gravel. How well loosely
arranged rock (such as sand and gravel) holds water depends on the size of the rock particles. Layers of loosely
arranged particles of uniform size (such as sand) tend to hold more water than layers of rock with materials of
different sizes. This is because smaller rock materials settle in the spaces between larger rock materials,
decreasing the amount of open space that can hold water. Porosity (how well rock material holds water) is also
affected by the shape of rock particles. Round particles will pack more tightly than particles with sharp edges.
Material with angular-shaped edges has more open space and can hold more water.

Groundwater is found in two zones. The unsaturated zone, immediately below the land surface, contains water
and air in the open spaces, or pores. The saturated zone, a zone in which all the pores and rock fractures are
filled with water, underlies the unsaturated zone. The top of the saturated zone is called the water table
(Diagram 1). The water table may be just below or hundreds of feet below the land surface.

What is an aquifer?

Where groundwater can move rapidly, such as through gravel and sandy deposits, an aquifer can form. In an
aquifer, there is enough groundwater that it can be pumped to the surface and used for drinking water,
irrigation, industry, or other uses. For water to move through underground rock, pores or fractures in the rock
must be connected. If rocks have good connections between pores or fractures and water can move freely
through them, we say that the rock is permeable. Permeability refers to how well a material transmits water.
If the pores or fractures are not connected, the rock material cannot produce water and is therefore not
considered an aquifer. The amount of water an aquifer can hold depends on the volume of the underground
rock materials and the size and number of pores and fractures that can fill with water.

ZONES OF AQUIFER:

Zone of Aeration
By definition, the zone of aeration is layer of Earth where the pores and cracks are filled with air and water. It
is sub-earthen region that exists between the Earth’s surface and water table. This zone mainly comprises
porous soil & rock. The pores in this layer are usually partially filled with water, while rest of them are filled
with air. Thus, in this layer, air and water are able to interact with each other, leading to aeration of water.
Therefore, this zone is known as zone of aeration.

The main source of water in this zone is the rainwater that has percolated through the layer of soil above, in a
process known as infiltration. In some cases, water from the water table is also able to rise into the aeration
zone, in a process known as capillarity. Capillarity results from the capillary action of the aeration layer where
water is able to climb against gravity from a wet particle to a dry one. In the zone of aeration, where water rises
and is held against gravity, is known as vadose zone, and the water in it is known as vadose water.

Zone of Saturation

By definition, the zone of saturation is a layer of permeable rock in which the cracks and pores are completely
filled with water. As the rainwater keeps penetrating the soil under the influence of gravity through the pores
of the aeration layer, it finally reaches the impermeable layer deep below the Earth’s surface. The composition
of this layer is such that further penetration is restricted and water is effectively trapped inside the pores of
the rocks present there.

As more and more water percolates down from the aeration layer to the impermeable layer, over a period of
time, the accumulated water saturates all the pores up to a certain height above the impermeable layer, forming
a new zone. This zone, where all the pores are completely filled with water, is known as the zone of saturation.

The uppermost portion of the zone of saturation is known as the water table or the phreatic surface. It forms
the dividing line between the zone of aeration and the zone of saturation. As the depth of the saturation layer
increases, the interconnected openings filled with water become so few, that they are almost non-existent.

The width of the zone of saturation may be very small in areas underlying consolidated rocks having joints
tapering at shallow depths or may be thousands of meters in areas underlying thick sedimentary formation

How does water fill an aquifer?

Aquifers get water from precipitation (rain and snow) that filters through the unsaturated zone. Aquifers can
also receive water from surface waters like lakes and rivers. When the aquifer is full, and the water table meets
the surface of the ground, water stored in the aquifer can appear at the land surface as a spring or seep.
Recharge areas are where aquifers take in water; discharge areas are where groundwater flows to the land
surface. Water moves from higher-elevation areas of recharge to lower-elevation areas of discharge through
the saturated zone.

How does water circulate?

Surface water and groundwater are part of the hydrologic cycle, the constant movement of water above, on,
and below the earth’s surface (Diagram 2). The cycle has no beginning and no end, but you can understand it
best by tracing it from precipitation. Precipitation occurs in several forms, including rain, snow, and hail. Rain,
for example, wets the ground surface. As more rain falls, water begins to filter into the ground. How fast water
soaks into, or infiltrates the soil depends on soil type, land use, and the intensity and length of the storm. Water
infiltrates faster into soils that are mostly sand than into those that are mostly clay or silt. Almost no water
filters into paved areas. Rain that cannot be absorbed into the ground collects on the surface, forming runoff
streams. When the soil is completely saturated, additional water moves slowly down through the unsaturated
zone to the saturated zone, replenishing or recharging the groundwater. Water then moves through the
saturated zone to groundwater discharge areas. Evaporation occurs when water from such surfaces as oceans,
rivers, and ice is converted to vapor. Evaporation, together with transpiration from plants, rises above the
Earth’s surface, condenses, and forms clouds. Water from both runoff and from groundwater discharge moves
toward streams and rivers and may eventually reach the ocean. Oceans are the largest surface water bodies
that contribute to evaporation.

How is groundwater contaminated?

Groundwater can become contaminated in many ways. If surface water that recharges an aquifer is polluted,
the groundwater will also become contaminated. Contaminated groundwater can then affect the quality of
surface water at discharge areas. Groundwater can also become contaminated when liquid hazardous
substances soak down through the soil into groundwater. Contaminants that can dissolve in groundwater will
move along with the water, potentially to wells used for drinking water. If there is a continuous source of
contamination entering moving groundwater, an area of contaminated groundwater, called a plume, can form
(Diagram 3). A combination of moving groundwater and a continuous source of contamination can, therefore,
pollute very large volumes and areas of groundwater. Some plumes at Superfund sites are several miles long.
More than 88 percent of current Superfund sites have some groundwater contamination.

How do liquids contaminate groundwater?

Some hazardous substances dissolve very slowly in water. When these substances seep into groundwater faster
than they can dissolve, some of the contaminants will stay in liquid form. If the liquid is less dense than water,
it will float on top of the water table, like oil on water. Pollutants in this form are called light non-aqueous phase
liquids (LNAPLs). If the liquid is denser than water, the pollutants are called dense non-aqueous phase liquids
(DNAPLs). DNAPLs sink to form pools at the bottom of an aquifer. These pools continue to contaminate the
aquifer as they slowly dissolve and are carried away by moving groundwater. As DNAPLs flow downward
through an aquifer, tiny globs of liquid become trapped in the spaces between soil particles. This form of
groundwater contamination is called residual contamination.
What affects groundwater contamination?

Many processes can affect how contamination spreads and what happens to it in the groundwater, potentially
making the contaminant more or less harmful, or toxic. Some of the most important processes affecting
hazardous substances in groundwater are advection, sorption, and biological degradation.

• Advection occurs when contaminants move with the groundwater. This is the main form of contaminant
migration in groundwater.

• Sorption occurs when contaminants attach themselves to soil particles. Sorption slows the movement of
contaminants in groundwater, but also makes it harder to clean up contamination.

• Biological degradation happens when microorganisms, such as bacteria and fungi, use hazardous
substances as a food and energy source. In the process, contaminants break down and hazardous substances
often become less harmful.

Why is cleaning up groundwater so hard?

Cleaning up contaminated groundwater often takes longer than expected because groundwater systems are
complicated and the contaminants are invisible to the naked eye. This makes it more difficult to find
contaminants and to design a treatment system that either destroys the contaminants in the ground or takes
them to the surface for cleanup. Groundwater contamination is the reason for most of Superfund’s long-term
cleanup actions. Diagram 4 illustrates groundwater treatment in action.
 “IMPORTANCE OF GROUND WATER IN CIVIL ENGINEERING”

Civil-engineering construction works often have a significant impact on groundwater conditions.

Such an impact can range from the derogation of water sources by dewatering works, to the creation of barriers
and pathways for groundwater flow formed by foundations or ground-improvement processes. In some cases,
not all these impacts are identified early enough during the planning and design process. This paper describes
the full range of potential groundwater impacts which can result from construction activities. The effects are
grouped into five rational categories as an aid to initial assessment. The need for accurate baseline groundwater
environmental data is set out. and recommendations are made for the planning of monitoring programs.

It is well established that civil-engineering projects can impact on the groundwater environment
during construction and in the longer term. The potential for some effects, such as the derogation of existing
groundwater sources during construction, are usually taken into consideration. Other changes, such as the
creation of flow pathways by pipeline or foundation construction are often not identified early in the planning
process.
 Groundwater can be viewed either as a resource worth protecting and managing or a problem
requiring a solution during below-ground works. Water-resource managers and hydrogeologists approach
ground-water primarily from the resource point of view, while construction engineers have traditionally
viewed the presence of groundwater as an inconvenience or problem, to be solved by suitable construction
expedients. Engineers adopt methods to mitigate the effect of groundwater, and this might include temporary
dewatering pumping or the construction of a physical cut-off wall into the aquifer. Some large structures
(basements, road or rail cuttings) below the water table might be equipped with permanent groundwater
drainage systems to prevent flooding, and lower the water table in the immediate vicinity with consequential
impacts which are not always fully appreciate

GROUNDWATER AS A RESOURCE

Groundwater is an important resource for beneficial use and for its inter- action with the wider
environment. In England, 33% of the public water supply is obtained from groundwater, in Wales 8%, in
Scotland 5% and in Northern Ireland 8% 13). These figures hide considerable local variations and, in addition,
groundwater is relied upon for domestic water supply from private springs and boreholes - even in regions
which have a low groundwater usage.

Origin and Occurrence of Earthquakes

What is an earthquake and what causes them to happen?

An earthquake (also known as a quake, tremor or temblor) is the shaking of the surface of the Earth
resulting from a sudden release of energy in the Earth's lithosphere that creates seismic waves. Earthquakes
can range in size from those that are so weak that they cannot be felt to those violent enough to propel objects
(and people) into the air, and wreak destruction across entire cities. The seismicity, or seismic activity, of an
area is the frequency, type, and size of earthquakes experienced over a period of time. The word tremor is also
used for non-earthquake seismic rumbling.

At the Earth's surface, earthquakes manifest themselves by shaking and displacing or disrupting the
ground. When the epicenter of a large earthquake is located offshore, the seabed may be displaced sufficiently
to cause a tsunami. Earthquakes can also trigger landslides and occasionally, volcanic activity.

Earthquakes are common geological phenomenon on planet Earth. Depending on the

magnitude, depth (focus) and area of occurrence (epicenter) are also responsible for natural disasters that
involve intense destruction of buildings and unfortunately the loss of human lives.

Earthquake, any sudden shaking of the ground caused by the passage of seismic waves through
Earth’s rocks. Seismic waves are produced when some form of energy stored in Earth’s crust is suddenly
released, usually when masses of rock straining against one another suddenly fracture and “slip.” Earthquakes
occur most often along geologic faults, narrow zones where rock masses move in relation to one another. The
major fault lines of the world are located at the fringes of the huge tectonic plates that make up Earth’s crust.

Earthquakes are caused by the sudden release of energy within some limited region of the rocks of
the Earth. The energy can be released by elastic strain, gravity, chemical reactions, or even the motion of
massive bodies. Of all these the release of elastic strain is the most important cause, because this form of energy
is the only kind that can be stored in sufficient quantity in the Earth to produce major disturbances.
Earthquakes associated with this type of energy release are called tectonic earthquakes.

An earthquake is what happens when two blocks of the earth suddenly slip past one another. The
surface where they slip is called the fault or fault plane. The location below the earth’s surface where the
earthquake starts is called the hypocenter, and the location directly above it on the surface of the earth is called
the epicenter.

An earthquake is caused by a sudden slip on a fault. The tectonic plates are always slowly moving, but
they get stuck at their edges due to friction. When the stress on the edge overcomes the friction, there is an
earthquake that releases energy in waves that travel through the earth's crust and cause the shaking that we
feel.
 Destructive earthquake of magnitude 7.9 that hit Sichuan Province, China,

in May 12, 2008. Deaths 69,195. Missing 18,392. Injured 374,643.

Earthquake Origins

Earthquakes can originate from sudden motion along a fault, from a volcanic eruption, bomb blasts,
landslides, or anything else that suddenly releases energy on or in the Earth. Not every fault is associated with
active earthquakes. Most faults are in fact no longer active but were active at some time in the geologic past. of
the active faults, only some are particularly prone to earthquakes. Some faults are slippery, and the two blocks
on either side just slide by each other passively without producing major earthquakes. In other cases, however,
the blocks stick together and deform until they reach a certain point at which they suddenly snap, releasing
energy in an earthquake event.

When big earthquakes occur, the surface of the Earth actually forms into waves that move across the
surface, just as in the ocean. These waves can be pretty spectacular and also extremely destructive. When an
earthquake strikes, these seismic waves move out in all directions, just like sound waves.

Types of fault
 Normal fault—the block above the inclined fault moves down relative to the block below the fault.
This fault motion is caused by tensional forces and results in extension.

Reverse fault—the block

above the inclined fault moves up relative to the block below the fault. This fault motion is caused by
compressional forces and results in shortening. A reverse fault is called a thrust fault if the dip of the fault plane
is small.

Strike-slip fault—movement of blocks along a fault is horizontal and the fault plane is nearly
vertical. Cause by shear forces.

Effects of Earthquakes

Shaking and ground

rupture

Shaking and ground rupture are the main effects created by earthquakes, principally resulting in
more or less severe damage to buildings and other rigid structures. The severity of the local effects depends
on the complex combination of the earthquake magnitude, the distance from the epicenter, and the local
geological and geomorphological conditions, which may amplify or reduce wave propagation.
Soil Liquefaction

Soil liquefaction occurs when, because of the shaking, water-saturated granular material (such as sand)
temporarily loses its strength and transforms from a solid to a liquid. Soil liquefaction may cause rigid
structures, like buildings and bridges, to tilt or sink into the liquefied deposits. For example, in the 1964 Alaska
earthquake, soil liquefaction caused many buildings to sink into the ground, eventually collapsing upon
themselves.

Human Impacts

An earthquake may cause injury and loss of life, road and bridge damage, general property damage,
and collapse or destabilization (potentially leading to future collapse) of buildings. The aftermath may bring
disease, lack of basic necessities, mental consequences such as panic attacks, depression to survivors, and
higher insurance premiums.

Landslides

Earthquakes can produce slope instability leading to landslides, a major geological hazard. Landslide
danger may persist while emergency personnel are attempting rescue.
Fires

Earthquakes can cause fires by damaging electrical power or gas lines. In the event of water mains
rupturing and a loss of pressure, it may also become difficult to stop the spread of a fire once it has started.

Tsunami

Tsunamis are long-wavelength, long-period sea waves produced by the sudden or abrupt movement of large
volumes of water—including when an earthquake occurs at sea.
 Floods

Floods may be secondary effects of earthquakes, if dams are damaged. Earthquakes may cause landslips to dam
rivers, which collapse and cause floods.

Harmful Effects of Earthquake to us Humans

i. They cause loss of human life due to collapse of buildings.

ii. Transport is affected due to disruption of railway and road systems.

iii. Infrastructure like buildings, dams and bridges develop cracks due to earthquakes.

iv. Earthquakes have economic effects like setback in trade and agriculture. Assets like houses and other
buildings are also destroyed.

v. Problems arise due to shortage of electricity. At the same time, underlying cables are disturbed leading to
disruption of communication systems.

vi. It becomes difficult to meet basic necessities of people like food and water.

vii. Water shortage also leads to rise of epidemics due to lack of proper sanitation.