The epicenter is the point on the Earth's surface directly above the hypocenter, which is the point where an earthquake originates underground. The word derives from Greek terms meaning "upon the center". The epicenter is above the earthquake's hypocenter and is usually the area of greatest damage, though larger earthquakes can cause damage hundreds of kilometers from the epicenter along the fault rupture zone. Magnitude measures the energy released by an earthquake at its source on the Richter scale, while intensity varies depending on location and is rated using the Modified Mercalli intensity scale.

1. The epicenter, epicentre / p s nt r/ˈɛ ɪ ɛ ə or epicentrum[1]
is the point on the Earth's surface that is
directly above the hypocentre or focus, the point where an earthquake or underground
explosion originates. The word derives from the New Latin noun epicentrum,[2]
thelatinisation of
the ancient Greek adjective πίκεντρος (ἐ epikentros), "occupying a cardinal point, situated on a
centre",[3]
from πί (ἐ epi) "on, upon, at"[4]
and κέντρον (kentron) "centre".[5]
The term was coined
by the Irish seismologist Robert Mallet.[6]
The epicentre is directly above
theearthquake's hypocentre (focus).In the case of earthquakes, the epicenter is directly above
the point where the fault begins to rupture, and in most cases, it is the area of greatest
damage. However, in larger events, the length of the fault rupture is much longer, and damage
can be spread across the rupture zone. For example, in the magnitude 7.9, 2002 Denali
earthquake in Alaska, the epicenter was at the western end of the rupture, but the greatest
damage occurred about 330 km away at the eastern end of the rupture zone.
What is the difference between Magnitude and Intensity?
Intensity: The severity of earthquake shaking is assessed using a descriptive scale –
the Modified Mercalli Intensity Scale.
Magnitude: Earthquake size is a quantitative measure of the size of the earthquake at its
source. The Richter Magnitude Scale measures the amount of seismic energy released by an
earthquake.
When an earthquake occurs, its magnitude can be given a single numerical value on the Richter
Magnitude Scale. However the intensity is variable over the area affected by the earthquake,
with high intensities near the epicentre and lower values further away. These are allocated a
value depending on the effects of the shaking according to the Modified Mercalli Intensity
Scale.

2. In an example, Magnitude can be likened to the power of radio or television waves sent out
from a broadcasting station. Intensity is how well you receive the signal, which can depend on
your distance from the energy source, the local conditions, and the pathway the signal has to
take to reach you.
It is a measure of earthquake size and is determined from the logarithm of the maximum
displacement or amplitude of the earthquake signal as seen on the seismogram, with a
correction for the distance between the focus and the seismometer.
Focus of an earthquake
The focus is also called the hypocenter of an earthquake. The vibrating waves travel away from
the focus of the earthquake in all directions. The waves can be so powerful they will reach all
parts of the Earth and cause it to vibrate like a turning fork.
1) Classification of faults on the basis of net slip
On the basis of net slip faults have the following three types
1. Dip slip fault
2. Strike slip fault
3. Oblique slip fault
a) Dip slip fault:
The faults in which the slip takes place along the direction of the
slip is called dip slip fault .in the dip slip fault net slip is parallel
to the dip of fault
b) Strike slip fault
The faults in which the slip takes place along the direction of
the strike is called dip slip fault .in the dip slip fault net slip
is parallel to the strike fault

3. c) Oblique strike fault
When the net slip is neither parallel to strike nor parallel to the dip of fault is called Oblique
strike fault.
OR
A fault which has a component of dip-slip and a component of strike-slip is termed an 'oblique-
slip fault'. Nearly all faults will have some component of both dip-slip and strike-slip, so defining
a fault as oblique requires both dip and strike components to be measurable and significant
2) Classification of faults on the basis of
apparent movement of blocks:
On the basis of the apparent movement of
blocks fault have the following types
1. Normal fault
2. Reverse fault
a) Normal fault
Normal fault is one in which the hanging wall falls down relative to the foot wall due to
tensional stress it is also called gravity fault/apparent normal fault. Normal faults with very
shallow dipping fault planes (<10 degrees) are called "detachment" faults or "decollemonts".
b) Reverse fault
Reverse fault is one in which the hanging wall moves up relative to the foot wall due to
compression. If the hanging wall is pushed up and then over the foot wall at a low angle it is
called a thrust fault. Reverse faults with very shallow dipping fault planes (<10 degrees) are
called "thrust" faults;

4. 3) Classification of faults on the basis of dip angle
On the basis of the dip angle fault has the following types
1. High angle fault
2. Low angle fault
a) High angle fault
A high angle fault is one that dips at angle greater than 45°
b) Low angle fault
A low angle fault is one that dips at angle smaller than 45°
4) Classification of faults on the basis of fault pattern
On the basis of pattern faults are classified
into the following types
1. Parallel faults
2. Step faults
3. Grabe or rift fault
4. Horst
5. Radial fault
6. Peripheral faults
7. Enechelon faults

5. a) Parallel fault
A series of faults running more or less parallel to one another and all handing in the same
direction, are called “parallel faults”
b) Step fault
It is consists of those parallel faults where down throw of all are in the same direction and it
gives a step like arrangement
c) Graben or Rift fault
When two normal faults fade towards each other and the beds between them are thrown
down in the form of a wedge, the structure is called graben or rift fault
d) Horst
A horst consists of a central block on the both sides of which adjacent beds appear to have
been faulted down
e) Radial faults
A number of faults exhibiting a radial pattern are described as radial faults
f) Peripheral faults
Curved faults of more or less circular, or are like outcrops on level surface are called peripheral
faults
g) Enechelon Faults
Enechelon fault are comparatively short faults which overlap each other
5) Classification of faults on the basis of altitude of fault relative to the altitude of the adjacent
rocks/formation
It can be classified as
1. Dip fault
2. Strike fault
3. Bedding fault
4. Oblique fault

6. 5. Tear fault or Tran current fault
a) Dip fault
A dip fault is one shore strike is parallel to the dip of strata and also called transverse faults
when it runs across the general structure o the region
b) Strike Fault
A strike fault is one shore strike is parallel to the strike of strata and also called longitude faults
when it runs across the general structure o the region
c) Bedding fault
When strike of the fault plane is oblique to the strike of dip of strata, it is called an oblique fault
e) Oblique fault
When the strike of the fault plane is oblique to the strike and dip of strata, it is called an oblique
Fault.
f) Tear fault or Tran current fault
It generally strikes transverse to the strike of country rocks .the fault plane is more or less
vertical and often extend fro along distances it is also called a wrench fault.
Types of water pollution
There are many types of water pollution because water comes from many sources. Here are a
few types of water pollution:
1. Nutrients Pollution
Some wastewater, fertilizers and sewage contain high levels of nutrients. If they end up in
water bodies, they encourage algae and weed growth in the water. This will make the water
undrinkable, and even clog filters. Too much algae will also use up all the oxygen in the water,
and other water organisms in the water will die out of oxygen starvation.
2. Surface water pollution
Surface water includes natural water found on the earth's surface, like rivers, lakes, lagoons and
oceans. Hazardous substances coming into contact with this surface water, dissolving or mixing
physically with the water can be called surface water pollution.
3. Oxygen Depleting
Water bodies have micro-organisms. These include aerobic and anaerobic organisms. When to

7. much biodegradable matter (things that easily decay) end up in water, it encourages more
microorganism growth, and they use up more oxygen in the water. If oxygen is depleted,
aerobic organisms die, and anaerobic organism grow more to produce harmful toxins such as
ammonia and sulfides.
4. Ground water pollution
When humans apply pesticides and chemicals to soils,
they are washed deep into the ground by rain water. This
gets to underground water, causing pollution
underground.
This means when we dig wells and bore holes to get
water from underground, it needs to be checked for
ground water pollution.
5. Microbiological
In many communities in the world, people drink untreated water (straight from a river or
stream). Sometimes there is natural pollution caused by micro-organisms like viruses, bacteria
and protozoa. This natural pollution can cause fishes and other water life to die. They can also
cause serious illness to humans who drink from such waters.
6. Suspended Matter
Some pollutants (substances, particles and chemicals) do not easily dissolve in water. This kind
of material is called particulate matter. Some suspended pollutants later settle under the water
body. This can harm and even kill aquatic life that live at the floor of water bodies.
7. Chemical Water Pollution
Many industries and farmers work with chemicals that end up in water. This is common
with Point-source Pollution. These include chemicals that are used to control weeds, insects
and pests. Metals and solvents from industries can pollute water bodies. These are poisonous
to many forms of aquatic life and may slow their development, make them infertile and kill
them.
8. Oil Spillage
Oil spills usually have only a localized effect on wildlife but can spread for miles. The oil can
cause the death to many fish and get stuck to the feathers of seabirds causing them to lose
their ability to fly.
Do you remember the BP Oil spill in 2010? (Read about it here) Over 1,000 animals (birds,
turtles, mammals) were reported dead, including many already on the endangered species list.
Of the animals affected by the spill, only about 6% have been reported cleaned, but many
biologists and other scientists predict they will die too from the stress caused by the pollution.

8. Continental Drift and Plate-Tectonics Theory
Source: U.S. Dept. of the Interior, Geological Survey
According to the theory of continental drift, the world was made up of a single continent
through most of geologic time. That continent eventually separated and drifted apart, forming
into the seven continents we have today. The first comprehensive theory of continental drift
was suggested by the German meteorologist Alfred Wegener in 1912. The hypothesis asserts
that the continents consist of lighter rocks that rest on heavier crustal material—similar to the
manner in which icebergs float on water. Wegener contended that the relative positions of the
continents are not rigidly fixed but are slowly moving—at a rate of about one yard per century.
According to the generally accepted plate-tectonics theory, scientists believe that Earth's
surface is broken into a number of shifting slabs or plates, which average about 50 miles in
thickness. These plates move relative to one another above a hotter, deeper, more mobile zone
at average rates as great as a few inches per year. Most of the world's active volcanoes are
located along or near the boundaries between shifting plates and are called plate-boundary
volcanoes.
The peripheral areas of the Pacific Ocean Basin, containing the boundaries of several plates, are
dotted with many active volcanoes that form the so-called Ring of Fire. The Ring provides
excellent examples of plate-boundary volcanoes, including Mount St. Helens.
However, some active volcanoes are not associated with plate boundaries, and many of these
so-called intra-plate volcanoes form roughly linear chains in the interior of some oceanic plates.
The Hawaiian Islands provide perhaps the best example of an intra-plate volcanic chain,
developed by the northwest-moving Pacific plate passing over an inferred “hot spot” that
initiates the magma-generation and volcano-formation process
Plate-Tectonics Theory—The Lithosphere Plates of Earth
This figure shows the boundaries of lithosphere plates that are active at present. The
double lines indicate zones of spreading from which plates are moving apart. The lines
with barbs show zones of underthrusting (subduction), where one plate is sliding
beneath another. The barbs on the lines indicate the overriding plate. The single line
defines a strike-slip fault along which plates are sliding horizontally past one another.
The stippled areas indicate a part of a continent, exclusive of that along a plate
boundary, which is undergoing active extensional, compressional, or strike-slip faulting.
Plate tectonics is the theory that Earth's outer shell is divided into several plates that glide over
the mantle, the rocky inner layer above the core. The plates act like a hard and rigid shell
compared to Earth's mantle. This strong outer layer is called the lithosphere.
Developed from the 1950s through the 1970s, plate tectonics is the modern version
of continental drift, a theory first proposed by scientist Alfred Wegener in 1912. Wegener didn't
have an explanation for how continents could move around the planet, but researchers do

9. now. Plate tectonics is the unifying theory of geology, said Nicholas van der Elst, a seismologist
at Columbia University's Lamont-Doherty Earth Observatory in Palisades, New York.
"Before plate tectonics, people had to come up with explanations of the geologic features in
their region that were unique to that particular region," Van der Elst said. "Plate tectonics
unified all these descriptions and said that you should be able to describe all geologic features
as though driven by the relative motion of these tectonic plates."
The driving force behind plate tectonics is convection in the mantle. Hot material near the
Earth's core rises, and colder mantle rock sinks. "It's kind of like a pot boiling on a stove," Van
der Elst said. The convection drive plates tectonics through a combination of pushing and
spreading apart at mid-ocean ridges and pulling and sinking downward at subduction zones,
researchers think. Scientists continue to study and debate the mechanisms that move the
plates.
Mid-ocean ridges are gaps between tectonic plates that mantle the Earth like seams on a
baseball. Hot magma wells up at the ridges, forming new ocean crust and shoving the plates
apart. At subduction zones, two tectonic plates meet and one slides beneath the other back
into the mantle, the layer underneath the crust. The cold, sinking plate pulls the crust behind it
downward. Many spectacular volcanoes are found along subduction zones, such as the "Ring of
Fire" that surrounds the Pacific Ocean.
Plate boundaries
Subduction zones, or convergent margins, are one of the three types of plate boundaries. The
others are divergent and transform margins.
At a divergent margin, two plates are spreading apart, as at seafloor-spreading ridges or
continental rift zones such as the East Africa Rift.
Transform margins mark slip-sliding plates, such as California's San Andreas Fault, where the
North America and Pacific plates grind past each other with a mostly horizontal motion.

10. Indoor Pollution
Indoor pollution is defined as "the presence of physical, chemical or biological contaminants in
the air of confined environments, which are not naturally present in high quantities in the
external air of the ecological systems." (Italian ministry for the Environment, 1991)
In the last thirty years much attention has been paid to reducing the outdoor pollution, but only
recently has the international scientific community worried about reducing the contamination
of the air of closed environments. If we consider the amount of time a person spends in a
closed environment (90%) we will understand that the issue of indoor pollution is of primary
importance.
The atmospheric composition inside an edifice is fundamentally the same we find outside, but
the amounts and types of contaminants differ. To the pollutants present outside one must add
all the polluting agents generated within the edifices.
The main sources of indoor pollutants are:
• construction materials
• heating, air-conditioning devices, and cooking apparatuses etc.
• furniture
• coatings (wall paint, varnish, floors etc.)

11. • maintenance and cleaning products (detergents, pesticides etc.)
• use of space and activities done within it
Outdoor air pollution can be defined as the presence of solids, liquids, or gases in outdoor air in
amounts that are injurious or detrimental to human health and/or the environment; or that
which unreasonably interferes with the comfortable enjoyment of life and/or property.
Outdoor air pollution has been recognized as a source of discomfort for centuries as smoke,
dust and obnoxious odors.
• Ozone (O3) – A free radical of oxygen (smog).
• Particulate matter – Sooty particles that are most toxic when they are small (<10
microns).
• Sulfur dioxide/sulfuric acid – Key component of acid rain.
• Carbon monoxide – Product of incomplete combustion.
• Nitrogen oxides – Common pollutants from burning of fossil fuels.
• Diesel exhaust – A mixture of particles, gases, and other chemicals.
• Polycyclic aromatic hydrocarbons – Chemical constituents of soot.
Greenhouse effect
The greenhouse effect is a natural process that warms the Earth’s surface. When the Sun’s
energy reaches the Earth’s atmosphere, some of it is reflected back to space and the rest is
absorbed and re-radiated by greenhouse gases.
Greenhouse gases include water vapour, carbon dioxide, methane, nitrous oxide, ozone and
some artificial chemicals such as chlorofluorocarbons (CFCs).
The absorbed energy warms the atmosphere and the surface of the Earth. This process
maintains the Earth’s temperature at around 33 degrees Celsius warmer than it would
otherwise be, allowing life on Earth to exist.
Enhanced greenhouse effect
The problem we now face is that human activities – particularly burning fossil fuels (coal, oil
and natural gas), agriculture and land clearing – are increasing the concentrations of
greenhouse gases. This is the enhanced greenhouse effect, which is contributing to warming of
the Earth.
The Greenhouse Effect, also referred to as global warming, is generally believed to come from
the build up of carbon dioxide gas in the atmosphere. Carbon dioxide is produced when fuels
are burned. Plants convert carbon dioxide back to oxygen, but the release of carbon dioxide

12. from human activities is higher than the world's plants can process. The situation is made worse
since many of the earth's forests are being removed, and plant life is being damaged by acid
rain. Thus, the amount of carbon dioxide in the air is continuing to increase. This buildup acts
like a blanket and traps heat close to the surface of our earth. Changes of even a few degrees
will affect us all through changes in the climate and even the possibility that the polar ice caps
may melt. (One of the consequences of polar ice cap melting would be a rise in global sea level,
resulting in widespread coastal flooding.) Additional resources and information about the
Greenhouse Effect and global warming are available from the Environmental Defense Fund
(EDF), the Science Education Academy of the Bay Area (SEABA) and the Society of
Environmental Journalists (SEJ).
Greenhouse effect
The greenhouse effect is the natural process by which the atmosphere traps some of the Sun's
energy, warming the Earth enough to support life.
Most mainstream scientists believe a human-driven increase in "greenhouse gases" is
increasing the effect artificially.
These gases include carbon dioxide, emitted by fossil fuel burning and deforestation, and
methane, released from rice paddies and landfill sites.
The Different Levels of the Atmosphere are:
Troposphere: This is the lowest atmospheric layer and is about seven miles (11 km) thick. Most
clouds and weather are found in the troposphere. The troposphere is thinner at the poles
(averaging about 8km thick) and thicker at the equator (averaging about 16km thick). The
temperature decreases with altitude.
Stratosphere: The stratosphere is found from about 7 to 30 miles (11-48 kilometers) above the
Earth’s surface. In this region of the atmosphere is the ozone layer, which absorbs most of the
harmful ultraviolet radiation from the Sun. The temperature increases slightly with altitude in
the stratosphere. The highest temperature in this region is about 32 degrees Fahrenheit or 0
degrees Celsius.
Mesosphere: The mesosphere is above the stratosphere. Here the atmosphere is very rarefied,
that is, thin, and the temperature is decreasing with altitude, about –130 Fahrenheit (-90
Celsius) at the top.
Thermosphere: The thermosphere starts at about 55 kilometers. The temperature is quite hot;
here temperature is not measured using a thermometer, but by looking at the motion and
speed of the rarefied gases in this region, which are very energetic but would not affect a

13. thermometer. Temperatures in this region may be as high as thousands of degrees.
Exosphere: The exosphere is the region beyond the thermosphere.
Ionosphere: The ionosphere overlaps the other atmospheric layers, from above the Earth. The
air is ionized by the Sun’s ultraviolet light. These ionized layers affect the transmittance and
reflectance of radio waves. Different ioniosphere layers are the D, E (Heaviside-Kennelly), and F
(Appleton) regions.

14. The Gaia hypothesis is an ecological hypothesis proposing that the biosphere and the physical
components of the Earth (atmosphere, cryosphere, hydrosphere and lithosphere) are closely
integrated to form a complex interacting system that maintains the climatic and
biogeochemical conditions on Earth in a preferred homeostasis. Originally proposed by James
Lovelock as the earth feedback hypothesis,[1]
it was named the Gaia Hypothesis after the Greek
supreme goddess of Earth.[2]
The hypothesis is frequently described as viewing the Earth as a
single organism. Lovelock and other supporters of the idea now call it Gaia theory, regarding it
as a scientific theory and not mere hypothesis, since they believe it has passed predictive tests
The Gaia hypothesis, also known as Gaia theory or Gaia principle, proposes that all organisms
and their inorganic surroundings on Earth are closely integrated to form a single and self-
regulating complex system, maintaining the conditions for life on the planet. The scientific
investigation of the Gaia hypothesis focuses on observing how the biosphere and the evolution
of life forms contribute to the stability of global temperature, ocean salinity, oxygen in the
atmosphere and other factors of habitability in a preferred homeostasis. The Gaia hypothesis
was formulated by the chemist James Lovelock and co-developed by the microbiologist Lynn
Margulis in the 1970s. Initially received with hostility by the scientific community, it is now
studied in the disciplines of geophysiology and Earth system science, and some of its principles
have been adopted in fields like biogeochemistry and systems ecology. This ecological
hypothesis has also inspired analogies and various interpretations in social sciences, politics,
and religion under a vague philosophy and movement.
The study of planetary habitability is partly based upon extrapolation from knowledge of the
Earth's conditions, as the Earth is the only planet currently known to harbour life.