Constituents and Structure, Processes of Nature, Natural Hazards and Disasters.pptx
1. GENERAL SCIENCE AND ABILITY
Syllabus Outline:
General Science:
a. Physical Sciences
b. Biological Sciences
c. Environmental Sciences
d. Food Sciences
e. Information Technology
General Ability:
a. Quantitative Ability/Reasoning
b. Logical Reasoning and Analytical Reasoning
c. Mental Abilities
4. Constituents and structure(+Origin):
_Universe
_Galaxy
_Light Year
_Solar System
_Sun
_Earth
_Astronomical Units
5. Astronomy is the study of the
universe and the celestial bodies,
gas, and dust within it.
Astrology The study of the
movements and relative positions of
celestial bodies interpreted as
having an influence on human affairs
and the natural world.
Cosmology The science of the origin
and development of the universe.
From the origin of the stars to the
origin of humans
6. UNIVERSE
The totality of everything that exists: all matter, energy, space, time, mass, stars,
air, mountains, etc.
ORIGIN OF UNIVERSE/ HOW DOES UNIVERSE FORMED?
a. Early Theories (directly focused on the development of earth)
When philosophers/ scientists started to think
o Nebular Hypothesis (1755)
o Laplace (Nebular) Hypothesis (1796)
o Planetesimal Hypothesis (1900)
b. Modern Theories (directly focused on the development of
Universe)
o Expanding Universe Theory/Big Bang Theory
o Steady State Theory
o Big Crunch Theory (the re-collapsing of the universe)
o Cyclic Theory (universe undergoes endless cycles of expansion
and cooling, each beginning with a big bang and ending in a big
crunch
7. EARLY THEORIES
NEBULAR HYPOTHESIS (1755)/ LAPLACE’S REVISION (1796)
Nebula: A cloud of Dust and Gases (H2, He)
It suggests the Solar System is formed from gas and dust orbiting a star (sun)
8. PLANETESIMAL HYPOTHESIS (1900)
Matter/planets were produced when a passing star almost collided with the sun.
During the near-collision, hot gases were pulled out of both stars and the gases then
condensed.
9. MODERN THEORIES (DIRECTLY FOCUSED ON THE DEVELOPMENT OF UNIVERSE)
A. BIG BANG THEORY (EXPANDING
FORMULATED BY: GEORGES LEMAITRE-A MATHEMATICIAN AND ASTRONOMER
Last and authentic theory about the formation of universe is the Big Bang Theory. It is a theory that
gives a cosmological explanation of the origin and expansion of the universe.
Big = Huge (Baraa)
Bang = Sound (Dhamaka)
Although some scientists say it was explosion, many agree that it was an expansion.
Explosion vs. Expansion
Explosion: (n.) A sudden outburst of something
Wave: - Wave is an energy carrier and can also be termed as energy.
Types: - There are two types of waves:
Mechanical wave: - They require medium for their propagation. E.g., Sound waves.
We do not hear the sound of explosions in the sun as there is a vacuum in
the atmosphere above the surface of the earth.
Electromagnetic wave: - They do not require medium for their propagation.
E.g., light reaching from the sun to earth although there is a vacuum in its path
Bang: - According to some scientist explosion has not occurred because with an explosion
there arises a sound but as there was no space and atmosphere then how can a sound be
generated. So, explosion has not occurred.
10. Big Bang Theory:
Steps/Stages:
According to the Big Bang Theory, the universe originated in the following steps:
1. Singularity
Single Primordial atom (point)
_Unimaginably Small Volume (negligible)
_Infinite Temperature
_Infinite Energy
_Infinite Density (Highly Compressed)
_(13.7 Billion Years Ago, singularity started expanding)
2. Expansion
With expansion
_Temperature is reduced (cooling)
_Time is originated (1st atom was formed in 1st three minutes)
_Energy is transformed into matter. (First quarks, subatomic Particles, Atoms,
Molecules, and so on.. { Quarks= Energy Packets}
3. Formation (after 300,000 years of expansion, temperature dropped to 4500K-
Enough to solidify atoms to form life.)
_Quarks rapidly combined to form groups of subatomic particles, which form the very
first element called Hydrogen.
_Hydrogen and dust particles of space combined to form stars. All other heavier
elements of the periodic table were formed by the massive stars at their explosion.
_Thus, the heavy elements combined to form new stars, new planets, and new life.
11. Singularity (All Energy)
↓
On expansion, energy started transforming into matter
↓
Small particles (very small, like quarks)
↓
Electrons (excited), protons, neutrons, and nucleus
↓
Electrons (stale)
↓
Atom (electrons came under the influence of nucleus)
↓
He
↓
H2
↓
Matter
↓
Universe
13. EVIDENCE TO SUPPORT BIG BANG THEORY
2. Hubble's law and Big Bang Theory:
By analysing the spectrum of light scientists proved that universe I
expanding
In 1920s, a telescope was formed by Edwin Hubble, with the help of which he observed::
a. There are galaxies other than Milky Way.
b. Distance between galaxies are constantly expanding without affecting the size of
galaxies. (Balloon)
Hence, galaxies are moving apart from each other with certain receding speed (the
speed with which someone moves backward slowly) proportional to the distance
between their centers as evidenced by the red-shift.
14. Speed ∞ distance between the centers of galaxies
Visible light has seven primary colors: VIBGYOR
Violet
Indigo
Blue ↑ energy increase
Green ↑frequency increases
Yellow ↑wavelength decreases
Orange
Red
According to a formula
E ∞ f
f= frequency and E= energy
E ∞
1
𝐿𝑎𝑚𝑑𝑎
where lamda = wavelength
When light coming from a star/ galaxy appears red, it means that the star is going away
from the source as the wavelength increases and energy decreases a characteristic of a
red light. The phenomena is known as Red Shift.
Nasa’s Hubble telescope is still in the lower orbit of earth, which observes processes in
space
Stars having high energy and
high frequency are blue hot; on
the other hand, the stars with
low energy are red
15. 3. The Presence of Cosmic Background Radiations:
Arno Penzias and Wilson detected cosmic BG radiations while studying radio
signal and declared them as leftover heat of BIG BANG.
Light Year:
(Measure of Distance NOT TIME)
Speed of light= 300,000 km/s
Light-year= 300,000+ 12 months (in seconds)
The distance between the earth and the sun
*Around 150 million km=8.311 light-minutes
On observation, every galaxy is moving away from the milky way galaxy- the
galaxy containing the earth as a planet.
However, two galaxies are moving towards one another, i.e., Milky Way Galaxy and
Andromeda due to mutual gravitational attraction. This mutual gravity force is
stronger than the force which causes the expansion of the Universe on the relatively
short distances between Andromeda and the Milky Way.
16. METHODS TO FIND THE AGE OF UNIVERSE
To estimate the age of the universe, scientists rely on two main methods.
a. Calculating the expansion rate of the universe
(Using Hubble’s Constant) Let us assume that universe is expanding at a constant speed
Hubble Noted:
The farther a galaxy was,
The faster it was moving away.
Scientists were then able to use the Hubble Constant to
estimate the age of the universe by working backward,
all the way back to the Big Bang.
b. Determining the age of the oldest stars
astronomers determine the age of stars by observing their spectrum, luminosity, mass, and motion
through space.
Blue Stars: High Energy and burns fuel easily: Red Stars: Low Energy
From this, they can determine how old a star is, and how much longer it has to live. This method of
determining star age can inaccurate because it relies on the accuracy of the models..
E.g. Globular clusters formed roughly around the same time. These clusters can then serve as timekeepers for the
universe. By determining the masses of their stars, scientists can estimate when the globular cluster formed.
17. COUNTER THEORIES/ ULTIMATE FATE OF
UNIVERSE
o Steady State Theory (Fred Hoyle: 1948)
o Big Crunch Theory (the re-collapsing of the universe)
o Cyclic Theory (universe undergoes endless cycles of expansion and
cooling, each beginning with a big bang and ending in a big crunch
18. Nebula: (Latin for Cloud)
Nebula is a cloud of dust particles and gases that occurs in interstellar space. It is also
called interstellar nurseries, a place where new stars are formed.
Types of Nebula:
There are five main types of nebulae:
1. Emission Nebula
A cloud of high temperature gas. Atoms excite and de-excite to absorb and emit radiation
respectively. Color based on the wavelength of emitted element.
e.g. Orion Nebula (M42).
2. Reflection Nebula
Does not emit radiations but reflect light energy from nearby stars. Reflection nebulae are frequently
the sites of star formation. They usually tend to be blue in color because of the way that the light is
scattered. Blue light is scattered more efficiently.
e.g. Trifid Nebula (M20) in Sagittarius
3. Dark Nebula
Blocks the light from the objects behind it.
e.g. Horsehead Nebula in Orion
4. Super Nova Remnant Nebula
when a star ends it life in a massive explosion known as a supernova. The explosion
blows a large amount of the star's matter out into space
e.g. crab Nebula (M1) in Taurus
5. Planetary Nebula
A shell of gas produced by a star as it nears the end of its life cycle.
Misleading name; has nothing to do with planet except shape
e.g. The Ring Nebula (M57) in Lyra
20. THE BIRTH OF NEW STARS FROM NEBULAE:
a. The dust and gases in a nebula are very spread out, but gravity can slowly
begin to pull together clumps of dust and gas.
b. As these clumps get bigger and bigger, their gravity gets stronger and
stronger.
c. Eventually, the clump of dust and gas gets so big that it collapses from its
own gravity.
d. The collapse causes the material at the center of the cloud to heat up-and
this hot core is the beginning of a star.
21. Dwarf Black Hole
Bodies left in the
atmosphere on the
destruction of small stars
When the center of a very
massive star(Super Novas_
with more than three solar
masses) collapses in upon
itself.
Black Hole:
Discovered by: John Michell & Pierre Laplace
Named by: Pierre-Simon
Since stars make their own light by fusion reaction of hydrogen and helium
in their core, the rate of reaction is directly proportional to the mass and
gravitational force.
m ∞ density and gravitational force
However, a time occurs when fuel of star ends; there is no fusion reaction
but still there is a mass, thus have strengthened gravitational force. Such
huge gravitation force does not allow light to be reflected. It is the main
reason, for Why black holes are black? A black hole is a region of space time
where gravity is so strong that nothing – no particles or even
electromagnetic radiation such as light – can escape
Boundary around Black Hole: Event Horizon
22.
23. GALAXY: BASIC UNIT OF UNIVERSE
Clusters of Stars, gases, space, interstellar space, dark matter, dust
particles
Distance between the galaxies is measured in Light Years
The number of galaxies ranges between 100 to 200 billion in number and
differ in range and size.
The number of stars vary in different galaxies.
Centre of every galaxy has a black hole.
The average diameter of a galaxy is one lakh light year.
24. Types of Galaxies: (Based on shape)
a. Spiral Galaxies
• Wide, flat disks of rotating gas and dust.
• Have wide flung arms
e.g. Milky way Galaxy (Solar System is in the orion arm of MilkyWay Galaxy)
b. Elliptical Galaxies
• Nearly Spherical shape and lack of overall structure
e.g. Cygnus A
c. Barrel Shaped Galaxies
• Mostly comprised of empty space, strange shape
e.g. M82 with its knotty structure
d. Irregular Galaxies
• Small, dwarf galaxies that lack any distinguishable shape
e.g. Large Magellanic cloud
Spiral Elliptical Peculiar Irregular
25. Asteroids:
Small, rocky objects that orbit the Sun like planets.
They are much smaller than planets. They are more rounded than comets
e.g. Ceres (a dwarf planet), Vesta, and Pallas.
Meteoroids:
Rocky object around sun even smaller than asteroids. They are made by the breakup of the asteroid and
comets.T hey can angular and circular
Meteorites:
meteoroids, asteroids, and comets that enter the atmosphere and survive to impact the surface. Relatively
recently, scientists had to amend the definition of a meteorite to only include natural solid objects falling to
the Earth from space.
Comets:
Cosmic snowballs of frozen gases, rock, and dust that orbit the Sun. More Elliptical than Asteroids.
They are different bodies moving around the sun. They are internally solids, but their outer surface is
gaseous.
And when they move around the sun, they make a tail of gases due to solar winds.
Their tail varies in size and can be up to 200 million kilo meter
Comet
26. DARK MATTER AND DARK ENERGY
Ordinary Matter: Everything we see in universe
Dark Matter/ Missing Mass: was originally discovered by Swiss American
astronomer Fritz Zwicky in 1933.
A component of the universe whose presence is discerned from
its gravitational attraction.
Dark Energy: A mysterious form of energy making up maximum of
universe and responsible for repulsion i.e. expansion of universe
27.
28. PLANET FORMATION
Stars= Localized clump of compressed gas
within a nebula (inshort stars made their
planets
1. The gravitational force of lump lead to the
formation of Core (of Star)
2. Nebular surroundings have their own gravity and density evolved a
platform for planet formation via condensation of gases and gravitational
attraction ( Disc of Gas around Core)
3. Accretion of matter on proto planets form
huge planets
29.
30. SOLAR SYSTEM
Solar Nebula: - A nursery, in which stars and planets are formed, is known as Solar
nebula. It is made up of gases and dust- solar dust
Solar Nebula Sun(star) Planets
Planet formation (4.6 Billion Years Ago)
On the Orion arm of the milky-way galaxy there is a star known as sun.
Because of high mass and gravity, the sun has compelled some other planets to
revolve around it
Components of Solar System:
1. One Star (Sun)
2. Eight Planets
3. Sixty three Moons
4. Dwarf Planet
5. Millions of Asteroids,
6. Dust Particles
7. Gases
31. THE SUN:
Mass of Sun: 1.989 × 10^30 kg (333,000 times the mass of the earth)
Diameter of Sun: 1.3927 million km (109 times the diameter of Earth.)
Distance from sun to earth: 150 million km
Surface Temperature: 5,778 K, 5500 degree Celsius
Radius of Sun: 696,340 km
Structure of Sun:
The percentage of Hydrogen is very much abundant in the sun and then the
percentage of the Helium exceeds other atoms.
Hydrogen in the sun = 70- 75%
Helium = 32- 34%
And the least abundant elements are Iron (Fe) and other materials.
32. LAYERS OF SUN:
• Core/Internal Zone/Inner Zone
Energy is generated via thermonuclear reactions creating extreme temperatures deep
within the Sun's core.
T: 15 million degrees Celsius
• Radiation Zone
Energy moves slowly outward, taking more than 170,000 years to radiate through this
layer of the Sun. (by thermal radiations)
• Convection Zone
Energy continues to move toward the surface through convection currents of the heated
and cooled gas.
• The Photosphere
The apparent part of sun that one sees in the sky when one looks at the Sun through a
telescope.
T= 5500 degree Celsius
• The Chromosphere
The chromosphere is the layer above the photosphere and is thicker than it. With a very
low density, it´s impossible to observe it without narrowband filters or during a total
solar eclipse due to the brightness of the photosphere behind it.
• The Corona
It is the biggest and least dense structure of the Sun made up of plasma. From Earth, the
corona is only visible during a total solar eclipse.
33. Solar Winds: continual stream of protons and electrons from
the sun's Corona
Solar Patches: relatively cool, dark patches on he surface of
sun
34. PLANETS:
1. All those bodies which do not have their own source of light, and they moves around the star of their
system in a particular orbit.
Planet word is derived from Greek word Planetes meaning wanderers
In our solar system, they are eight in number.
My Very Efficient Mother Just Served Us Noodles
Mercury
Venus
Earth
Mars
Jupiter
Saturn
Uranus
Neptune
Out of the eight
04 = Inner planets/ terrestrial planets/ Rocky planets
04 = Outer planets/ Jovian planets/ gasious planets
Asteroid belt: There is a belt between the inner and outer planets, which is known as the Asteroid belt. The
belt is present between the Mars and Jupiter.
36. PHYSICAL CHARACTERISTICS OF PLANETS
https://nssdc.gsfc.nasa.gov/planetary/factsheet/planet_table_british.html
37. • Mercury is about the same size as our moon (Smallest)
• Venus: Hottest and Brightest
(Hot: due to the heavy spinning clouds of CO2 Bright: due to high reflection of light)
• Earth: Most colorful and the densest
Biggest among terrestrial planets
Fifth largest in solar system
Only Planet that supports life
• Mars: Second Smallest
Red Planet
• Jupiter: Biggest
1350 times bigger than earth
318 times massive than earth
Ganymede moon of Jupiter is the largest moon of our solar system
• Saturn: Second Biggest Planet
The ring Planet
• Uranus: Green Planet
Uranus and Neptune are called twin planets
38. DWARF PLANET/ WHY PLUTO IS NOT CONSIDERED A PLANET?
According to International Astronomical Unit, Planet is a celestial body a. That
orbit around the sun
b. That has gravitational pull must be strong enough that it pulls the object into a
spherical shape.
c. That is massive enough to clear its orbit of debris.
A Dwarf planet is the one that has not cleared the area around its orbit because
of small planet. There are only five dwarf planets in our solar system: Ceres,
Pluto, Haumea, Makemake, and Eris.
Pluto is now classified as a dwarf planet because, while it is large enough to have
become spherical, it is not big enough to exert its orbital dominance and clear
the neighborhood surrounding its orbit.
39. ASTRONOMICAL UNITS:
The mean distance between the sun and earth
Sun
Earth
1 AU= 150 million km
The Light Year is about 64,500 times larger than the Astronomical Unit
1 Light Year = 63,000 AU
40. ASTRONOMICAL SYSTEM OF UNITS
A system of measurement developed for use in astronomy. It is a tridimensional system, in that it defines
units of length, mass and time.
Tridimensional
Length Time Mass
The astronomical unit of
length is AU, and
1AU = average distance
between the sun and
the earth
1AU = 150 million Kms
The astronomical of time is
the Day, and
1 Day = one unit
One Day = 86400 secs
One year = 365.25 days
The astronomical unit of
mass is solar
mass, and
1 solar mass = mass of the
sun
1 solar mass =
1.98892×1030
kg
41. MOON
• Moon is a natural satellite.
• A satellite is an object revolving around the earth in a fixed orbit.
• Earth has one moon- a permanent natural satellite
• Gravity of the moon is 1/6 of the earth’s gravity.
• It is the moon producing tides in the sea because of the gravitational
pull of the earth., thus tides are longer at night.
42. Moon’s one revolution around the earth=27.3 days
Orbit around the earth=elliptical, like an egg.
No atmosphere
No Self Light
Time of light to reach the earth from the moon = 1.3 seconds
Two points in the orbit of the moon around the earth:
a. Apogee:
The point where the distance between the moon and the earth is
maximum.
b. Perigee:
The point where the distance between the moon and the earth is
minimum.
43. ECLIPSES:
1. Lunar Eclipse:
The obscuring of one astronomical object by another is called eclipse.
The obscuring of light of moon by the interaction of the earth
between the sun and the moon is called lunar eclipse.
1. Complete lunar eclipse
When the entire moon passes through the umbra region(------) of the earth
2. Partial lunar eclipse
When the partial moon passes through the umbra region of the earth
44. Umbra and Penumbra:
During eclipse, two shadows are formed:
1. Umbra: It is the dark center of the eclipse shadow. This shadow
gets smaller as it goes away from the sun.
2. Penumbra: a Partial shadow that gets larger as it goes away
from the sun.
3. Penumbral lunar eclipse
When moon passes through the penumbra region of the earth
45. 2. Solar Eclipse:
It occurs when moon comes in between the earth and the sun
resulting in the formation of shadow on the earth.
1. Total Solar eclipse
When moon entirely covers the sun. Can be observed from a very small area of
earth. Alignation of sun, moon, and earth.
The lovely diamond ring effect is observed in total solar eclipse. After sometime,
when moves away a single step from the front of the sun, it shows some kind of
Baili’s bead after the name of the scientist Baili.
https://www.youtube.com/watch?v=wkmdedxydVA
46. 2. Partial Solar eclipse
When the moon partially covers sun. The sun, earth, and moon do not align in
straight line.
3. Annular Solar eclipse:
When the Moon is farthest from Earth. Because the Moon is farther away, it
seems smaller. It does not block the entire view of the Sun. The Moon in front of
the Sun looks like a dark disk on top of a larger Sun-colored disk. This creates
what looks like a ring around the Moon.
47. Why Don't We Have an Eclipse Every Month?
Because the Earth's orbit around the sun is not in the same plane as the
Moon's orbit around the Earth.
48. Because the Moon's shadow moves at
1,700 kilometres per hour! A total solar
eclipse occurs on Earth roughly every 18
months.
Solar Eclipse Lunar Eclipse
49. GEOGRAPHIC COORDINATE SYSTEM
A geographic coordinate system (GCS) uses a three-dimensional spherical
surface to define locations on the earth.
Pole= +/-90 degree Latitude
Equator= 0 degree Latitude
51. ZONES OF LATITUDE:
1. Torrid Zone:/Tropic
Between tropic of cancer and tropic of Capricorn where there sun remains
overhead- Heat Surplus Zone
2. Frigid Zone:
Zones toward south and north pole- (heat deficit on both sides)
3. Temperate Zone:
Zones between torrid and frigid zones called Temperate Zone (on both
sides)
The 7 significant latitude lines:
1. Equator 0 degree
2. Tropic of Cancer 23.5 degree N
3. Tropic of Capricorn 23.5 degree S
4. Arctic Circle 66.5 degree N
5. Antarctic Circle 66.5 degree S
6. North Pole 90 degree N
7. South Pole 90 degree S
52. Null Island is the point on the Earth's surface at zero degrees latitude and
zero degrees longitude ( 0°N 0°E), i.e., where the prime meridian and the
equator intersect.
53. EARTH-SUN RELATIONS
ROTATION/SPIN:
Earth rotates from west to east ( Counter Clockwise) on its axis with the tilt of
23.5 degree centigrade
• It is responsible for the occurrence of days and nights.
• It takes about 23 hrs, 56 minutes, and 4 seconds
54. REVOLUTION:
Revolution of the earth is responsible for the occurrence of seasons, like summer
and winter.
It takes 365.25 days to complete one revolution around the sun. The seasons vary
in the south and the north of the globe.
55. SEASONS
The seasons occur because the axis on which Earth is tilted with respect to the
plane of the Earth’s orbit around the sun.
Earth’s tilt causes the north pole to be tilted toward the sun for half of the year, and
the south pole to be tilted towards the sun for the other half of the year.
57. THE EARTH
Around 4.5 billion years ago, Milky Way had star, and some planets started
moving around the star- the sun- in a fixed orbit.
The study of the earth, its composition, and structure is known as Geology, and the
persons who studies or works on geology are known as Geologists.
• Initially, the Earth was none other than barren land, with the passage of time, a
series of endogenous and exogenous events happened to form a present day
layered structure distributed in multiple spheres consisting of water, land, life, etc.
Spheres of earth:
1. Lithosphere (stone)
2. Hydrosphere (Water)
3. Atmosphere (smoke or vapor)
4. Biosphere (life)
Endogenous: forces from within the Earth
Exogenous: forces on or above the Earth’s surface.
58. Layers are separated on the basis of density as well as chemical composition, thus
highly dense material aggregate in the core.
Compositionally, Layers of earth
1. Crust:
a. Oceanic Crust
b. Continental Crust
2. Mantle:
a. Outer Mantle
b. Inner Mantle
3. Core:
a. Outer Core
b. Inner Core
LAYERS OF EARTH’S INTERIOR
Mechanically, Layers of interior earth:
1. Lithosphere
2. Asthenosphere
3. Mesosphere
4. Barysphere (core)
59. 1. CRUST: (50-70 KM THICKNESS)
• Least Density
• Least Volume
• Thinnest layer ( the layer we live on)
a. Oceanic Crust 2/3rd (made of SIMA: silicon + magnesium)
Relatively thick-
b. Continental Crust 1/3rd (made of SIAL: silicon + Alumina)
Due to density variation b/w continental and oceanic crust, there is
a discontinuity in plates: Conrad Discontinuity
Crust is divided into large chunks called plate tectonics that float on
the mantle beneath them.
60. 2. MANTLE (2900 KM THICKNESS)
• Thickest layer of earth (80 % of the volume of earth/ 67 % of the
mass of earth)
• Made of SIMA (silicon + magnesium)
Volcanic eruption comes from Mantle to the mid-ocean ridges
Mid-Ocean Ridges: a place where tectonic plates separate from each other
Due to density variation b/w mantle and crust, there is a discontinuity in
plates: Moho Discontinuity
• Upper Mantle
-Asthenosphere ( solid layer of upper mantle)
• Lower Mantle
Asthenosphere + crust= Lithosphere
Due to density variation b/w upper mantle and lower mantle, there is a
discontinuity in plates: Repiti Discontinuity
Upper Mantle + Lower Mantle = Mesosphere
61. Lava Vs. Magma: -
The Iron present in the lower mantle is found in the liquid
state, known as Magma.
But, if the Magma erupts out of the earth’s surface, the
Magma is, now, known as Lava.
62.
63. 3. CORE (5100 KM THICKNESS)
Due to density variation b/w inner core and outer core, there is a discontinuity
in plates: Lehmann Discontinuity
Due to density variation b/w lower mantle and outer core, there is a
discontinuity in plates: Gutenberg’s Discontinuity
• Highly Dense
• Made of NIFE (nickel & Ferrous)
a. Outer Core (Earth’s magnetic field is due to outer core because iron
rotate krta hai)
Majority Liquid
b. Inner Core
Majority Solid: Due to high pressure of rocks and high centripetal force
(remaining latent heat outside to form liquid
64. Earth’s layer Mass distribution Volume Distribution Thickness Composition
Crust 11 % 11 % 50-70 KM SIAL
Mantle 67 % 83 % 2900 KM SIMA
Core 32 % 16 % 5100 KM NIFE
Centre - - 6300 KM -
65. EARTH MATERIALS AND THE CYCLE OF ROCK CHANGE
The most abundant elements in the Earth ’s crust: oxygen, silicon, aluminum, iron, calcium,
sodium, potassium, and magnesium.
The elements combine with one another to form minerals and exist in a variety of rock
combinations
A mineral is a naturally formed solid, inorganic substance with a characteristic crystal
structure and chemical composition.
Eg. Oxides, Carbonates, Sulphides, Sulphates, Chlorides, etc.
5 characteristics required of all minerals:
1. Be naturally-occurring
2. Be Inorganic
3. Be solid at room temperature
4. Have a typical ordered internal structure
5. Have a definite chemical composition
Physical Properties of minerals:
1. Cleavage: The tendency of a mineral to break (cleave) along weak planes.
2. Color: Most minerals have a distinct color while others are variable in color.
3. Hardness: A measure of a mineral's resistance to scratching.
4. Luster: The reflection of light from the surface of a mineral, described by its quality and
intensity. Luster is described as metallic, glassy, dull, earthy, etc.
5. Streak: refers to the color of the residue left by scratching a mineral on a tile of unglazed
porcelain, like a piece of chalk.
66. ROCKS
An aggregate of minerals
Types of Rocks:
1. Igneous Rocks:
Formed by cooling and solidification of magma. (magma to lava)
Eg. Granite, Basalt, etc.
Types of igneous rocks on the basis of origin
a. Intrusive igneous rocks:
Magma that solidifies below the Earth ’s surface and remains surrounded by older, preexisting
rock is called intrusive igneous rock. Eg. Dolomite
Solidify slowly
Coarse texture
Larger in size
b. Extrusive Igneous rocks:
If the magma reaches the surface and emerges as lava, it forms extrusive igneous rock. Eg.
Basalt.
Solidify at faster pace
Smooth, crystalline, and fine grained
Small in size
67. Types of igneous rocks on the basis of chemical composition
a. Acidic Igneous Rocks:
They are rich in silica, sodium, and potassium.
Poor in calcium, magnesium, and iron.
They are light in color
Low density
Low specific gravity
E.g., granite
a. Basic Igneous Rocks:
They are poor in silica, sodium, and potassium.
Rich in calcium, magnesium, and iron.
They are dark in color
They have high density
They have high specific gravity
e.g., Basalt
68. 2. Sedimentary Rocks:
Formed by consolidation and cementation of sediments deposited by water, air, glaciers, etc.
(Weathering: Decomposition and breakup of rocks)
Eg. Sandstone, Limestone
Types of Sedimentary rocks:
a. Mechanically formed sedimentary rocks
It is derived from mechanics or motion, like with the help of flowing water.
e.g., sand stone
b. Organically formed sedimentary rocks (organic rocks vs. fossils)
They consist of plant or animal remains.
Calculus: contain calcium or calcium shells as the essential element in excess.
e.g., lime stone (CaCO3)
Carbonaceous: contain high amount of carbon
e.g., coal seam
c. Chemically formed sedimentary rocks
They are formed due to the precipitation and accumulation of soluble constituents
Carbonate rocks: contain carbon as a major component
e.g., CaCO3 = lime stone
Sulphate rocks: have sulphate as their major component
e.g., Gypsum
Chloride rocks: have chloride as the major component
e.g., NaCl = rock salt
69. 3. Metamorphic Rocks
Formed when pre-existing rocks have been changes in texture and composition by
increased temperature and pressure
Eg. Marble, Gneiss, etc.
METAMORPHISM
E.g., Lime stone ======================> Marble (metamorphic form)
Granite ======================> Gneiss (metamorphic form)
Agents of metamorphism:
There are two types of agents responsible for metamorphism.
a. Physical agents
The are heat and pressure. Because of the physical changes, they produce new texture.
b. Chemical agents
They are chemically active water and gases. They form new rocks.
All the process is known as the process of recrystallization.
70. THE CYCLE OF ROCK CHANGE
Rocks are constantly being transformed from one class to another in the cycle of
rock change.
a rock formation that is visible on the surface
71. GEOMORPHOLOGY
A Scientific theory that explains how major landforms are created as a result of
Earth's subterranean movements. According to plate tectonics, earth plates (Crust)
are divided into 7 major and minor plates continuously floating to magma
(Asthenosphere: Weak zone of mantle) leading to Folding, faulting, and volcanoes
Plate tectonics theory
It was given by the Alfred Wegner in 1960
Types of plates:
1. Convergent plates:
Convergent means coming towards one another
Folding: Mountains formation (C-C plates)
2. Divergent plates:
Divergent means moving away from one another
3. Transform boundary:
In this, plates slide past each other
Earth Quakes, Volcanoes (mostly at plate boundaries-crack area)
Movement is directly prop. to Temperature
72.
73. SOURCES TO DETERMINE THE EARTH’S
INTERIOR
1. Direct Sources:
a. Deep Earth Mining
b. Volcanic Eruption
2. Indirect Sources:
a. Increase in pressure and temperature with depth
b. Seismic Waves (energy that is released in earth interior)/ Earth Quake
74. Vibration Waves that travel through Earth's layers as a result of earthquakes, volcanic
eruptions, magma movement, large landslides and large man-made explosions that
give out low-frequency acoustic energy.
There are two types of seismic waves:
1. Body Waves
A seismic wave that moves through the interior of the earth
a. Primary Waves ( P waves)- Compressional: Fastest: Dog’s Detect
b. Secondary Waves (S waves)- Shear: 2nd Fastest: Perpendicular
2. Surface Waves
A surface waves that travel near the earth's surface
a. Love Waves (L waves)-Perpendicular Side ways
b. Rayleigh Waves (R waves)-Slowest: Highly destructive: to and forth movement of
earth
https://www.britannica.com/science/Earth-tide
75. 1. EARTH QUAKES:
The shaking of Earth caused due to the
movement of tectonic plates, releasing
energy in the form of Seismic waves.
Seismos: To Shake
The study of earthquakes and the waves
they create is called seismology
The surface where the plates slip: Fault line
The surface where the earth quake start: Hypocenter/
the focus
The Surface directly above the hypocenter: Epicenter
Major Natural Disasters
A sudden and terrible event in nature
(Such as a hurricane, tornado, or flood)
that usually results in serious damage
and many deaths.
76. Based on scientific purposes, this earthquake depth range of 0 - 700 km is divided
into three zones:
a. Shallow (originate within 60 km (40 miles) of the Earth’s outer surface.)
b. Intermediate (depth of the origin is between 60 to 300 km)
c. Deep (depth of the origin is greater than 300 km)
Causes of Earth Quake:
1. Tectonic movements
Earthquakes occur along fault lines, cracks in Earth's crust where tectonic plates
meet- sub duct, spread, slip, or collide. As the plates grind together, they get
stuck and pressure builds up. Finally, the pressure between the plates is so great
that they break loose.
2. Eruptions of volcanoes
3. When an asteroid collides with the Earth’s atmosphere
4. Under ground nuclear blasts
Classification of Earth Quake:
77. Measurement of Earth Quake:
Earthquake ranges from tremors to great shocks.
a. By intensity (Damage) –intensity changes with distance
Calculated on Mercalli Scale
b. By magnitude = Energy released in the form of waves
Seismograph: detect vibration caused by earthquake: plot the vibration on paper
Richter Scale: magnitude/ strength is measured using Richter Scale.
Seismologist Charles F. Richter of California in 1935 created
Richter scale using the logarithm of the largest seismic wave’s
amplitude to base 10. Richter’s scale was originally for
measuring the magnitude of earthquakes from magnitudes
ranging from 0 to 10.
79. Management of Earthquake damages:
1. Risk Assessment
Inspect, evaluate, and document the risk associated with building in
earth-quake prone areas
2. Risk Zoning
Countrywide Seismic micro-zonation
-Red Area: No construction is allowed
-Yellow: Single story buildings are allowed
-Green: Safe buildings
3. Planning
-Maintain a better planning and construction
4. Research & management
-Budget for the research and development of quakes
5. Public Awareness
-Awareness programs for local public
6. Legislation
-Approve legislation covering natural hazards
7. Emergency Management
-Prioritize emergency preparedness
80. 2. VOLCANISM
The eruption of molten rocks erupts from inside the Earth to the surface.
Volcano is essentially the vent on the earth’s crust.
The word volcano is derived from Vulcan: a roman god of Fire
molten magma- is erupted due to the density variation and reaches the surface as lava.
It cools and hardens in the form of a dome or crust (Cone shape mountain)
https://www.the-sun.com/lifestyle/tech-old/265721/what-causes-a-volcano-to-erupt-
how-they-formed-and-different-types-of-volcano-revealed/
For Example:
The Pacific Ring of Fire includes
two-thirds of the world’s volcanoes
Mount Pinatubo, Philippines
Mount Etna, Italy (etc.)
A crater is a funnel-shaped pit around
the central vent at the top of a volcano
81. Causes of volcanic eruption:
Most volcanoes appear along the sides of the tectonic plates- plates that make up the surface of
the world.
1. Plates movements:
a. At diverging plate boundaries, ( CONSTRUCTIVE) where mantle beneath plates is hot but
remains solid because it is under great pressure. As the hot mantle rises, sudden drop in
pressure causes melting, much as taking the lid off a pressure cooker causes super-heated
water to flash to steam.
Rifting
b. At convergent plate boundaries, ( DESTRUCTIVE) as one plate dives (sub ducts) beneath the
other, it heats up and releases hot. The fluids (mostly water) rise, wetting hot rock in their path and
causing some of the rock to melt.
Subduction
82. 2. The pressure from the saturated gases in the magma:
The magma, in the interior of the earth, is often saturated with gases like carbon
dioxide, and hydrogen sulfide. When the gases exert pressure together with water
vapors, the highly explosive magma is forced out as lava in the form of hot spot on the
surface of the earth. (not necessarily at plat boundary
Hotspot
83. Types of Volcanoes:
Volcanoes are grouped into four types based on their shapes:
1. Cinder cones volcanoes
Circular or oval cones made up of small fragments of lava from a single vent
2. Composite volcanoes/Stratovolcanoes
Steep-sided volcanoes composed of many layers of volcanic rocks
3. Shield volcanoes
Shape like a bowl or shield in the middle with long gentle slopes
4. Lava volcanoes
Steep-sided mound as the lava piles up near the volcanic vent.
84. Effects of Volcanoes:
1. Positive Effects
a. To produce geothermal energy
b. Ash as a fertilizer
c. Attract many tourists
d. Helps build new islands
2. Negative effects:
a. Causes abrupt temperature changes
b. Damage Vegetation
c. Cause severe respiratory problems to humans
d. Aggravate earthquakes, tsunamis, and other natural calamities.
85. 3. TSUNAMI
Tsunami: Harbour waves
Also called Sea-quakes
Abnormal sea waves that can cause catastrophic damage when it hit coastline
Causes of Tsunami:
1. Undersea earthquakes: (cause 80 percent of tsunamis)
up and down movement of tectonic plates (side by side movements do not
cause tsunamis)
2. Volcanoes
3. Asteroid crashing into ocean
4. Undersea landslide
Condition of Tsunamis:
1. Earthquake must measure at least 7 on Richter Scale
2. Seabed must be lifted or lowered by earthquake
3. Epicentre of earthquake must be near to the coastal area
86. Characteristics of Tsunami:
1. Earth’s most infrequent hazards
2. Most of them are small and nondestructive.
3. Wavelength is directly proportional to the depth
4. Wave height of tsunami ranges from a few centimeters to over 30 m in
height.
5. Radiates in all directions from the point of origin
6. There is no season for tsunamis and not all tsunamis act the same. It
cannot be predicted where, when and how destructive it will be.
7. Speed of tsunami is directly proportional to depth. Hence, impacts are
more near coastlines than in deep oceans
87. Effects of Tsunami:
a. Flooding and erosion
b. Shorten the coastline
c. Erodes both landscapes and human structures
-The initial wave of tsunami is extremely tall
d. Diseases and deaths
e. Psychological Impacts
f. Economic losses
g. Environmental effects
https://www.sms-tsunami-warning.com/pages/tsunami-effects#.Yr3A2HbMI2w
88. 4. AVALANCHE:
A sudden downhill movement of snow
Causes of Avalanche:
1. Heavy Snowfall
2. Deforestation
3. Steep slopes
4. Vibrations (earthquakes)
5. Layering of snow
6. Wind Direction
Effects of Avalanche:
1. Loss of life
2. Loss of property
3. Blockage of road traffic
4. Loss of communication links
5. Blockage of small rivers as a threat of flood
89. Types of Avalanche:
1. Loose snow Avalanche:
Common on steep slopes
Fresh Snow
2. Slab Avalanche:
The fall of a large block of ice down the slopes
The most dangerous Avalanche
3. Powder Snow Avalanche:
Mix of the other forms, Loose Snow and Slab
Above this is a cloud of powdered snow, which can snowball into a larger
avalanche as it progresses down the slope
4. Wet Snow Avalanche:
Quite dangerous as they travel slowly due to friction, which collects debris from
the path fairly easily.
5. Gliding Avalanche:
Like slab avalanches, gliding avalanches have a distinct, broad fracture line, but
they differ inasmuch as the entire snowpack is released
91. 5. FLOODS:
An overflow of water that submerges land that is usually dry
Causes of Floods:
a) NATURAL CAUSES
1. Intense Rainfalls
2. Cloudbrusts
3. Volcanic eruption causing glacier meltings
4. Cyclones
5. Impermeable surfaces
6. Land Erosion
(b) ANTHROPOGENIC CAUSES
1. Urbanization
2. Population growth
3. Dam breaks
4. Deforestation
5. Climate change
92. Effects of Floods:
a. Primary Effects:
1. Loss of infrastructure
2. Loss of lives
3. Loss of resources
b. Secondary Effects:
1. Landslides
2. Soil Erosion
3. Health Issues
c. Tertiary Effects:
1. Poverty
2. Food Shortage
3. Economic Stress
93. Management of Flood:
1. Construction of Dams
2. River Engineering
3. Afforestation
4. Reforestation
5. Urban Planning
6. Awareness
94. 6. DROUGHT
Deficiency of rainfall over extended period
Causes of Drought:
1.Lack of rainfall
2. Dry Seasons
3. Climate change
4. Deforestation
5. Mismanagement of resources
Effects of Drought:
1. Diminished crop growth
2. Food shortage and famine
3. Habitat damage, affecting wildlife
4. Malnutrition, dehydration
5. Mass migration
6. Desertification
7. Wildfires
8. Loss of life
9. Economic Loss
95. Management of Drought:
1.Dams (save water for drought)
2. Desalination (additional water for irrigation)
3. Drought Monitoring (cont. observation of
rain patterns)
4. Land use planning
5. Outdoor water-use restriction
6. Rain water harvesting
7. Recycled water
8. Water conservation
7. WILD FIRE* / 8.URBAN FIRE*
96. ATMOSPHERE:
The state of the atmosphere, describing for example the degree to which it is
hot or cold, wet or dry, calm or stormy, clear or cloudy.
Conditions of the atmosphere are over a short period of time.
Climate:
Conditions of the atmosphere are over a long period of time
Weather:
The gas and aerosol envelope that extends from the ocean, land, and ice-covered
surface of a planet outward into space.
Meteorology: The study of the atmosphere and motions within the atmosphere
on short-time scales
**TO BE COVERED IN ENVIRONMENTAL SCIENCE PORTION**
The natural movement of air or other gases relative to a planet's surface and is
caused by differences in air pressure within our atmosphere. (from high
pressure area to low pressure area.
Wind:
97. GLOBAL WIND PATTERNS
Wind is the outcome of a thermodynamic principle due to the counterclockwise rotation of the
earth.
*Large global wind systems are created by the uneven heating of the Earth’s surface-The warm
temperature at the equator and cold temperature at the poles.
• Near the equator: the sun is almost directly overhead for most of the year. Warm air
rises at the equator and moves toward the poles.
• At the poles: the cooler air sinks and moves back toward the equator.
THE PROCESS IS NOT AS SIMPLE AS IT APPEARS. The wind moves via the PROCESS CALLED
CORIOLIS EFFECT- the apparent shift in the path of any fluid or object moving about the
surface of the Earth due to the rotation of the Earth.
The latitude where Earth’s mean annual
surface temperature is highest is located at
10°N.
The Northern Hemisphere has more landmass
and is relatively warmer than the Southern
Hemisphere
98. The surface winds of each hemisphere are divided into Three Wind Belts:
1. Polar Easterlies:
a. From 60-90 degrees latitude.
b. Exists at North and South pole at higher latitute
c. Cooler air forms at poles and sinks to equator
2. Prevailing Westerlies:
a. From 30-60 degrees latitude
b. Here, winds floes from west to east
c. Clement part of the earth (Steady winds)
3. Tropical Easterlies/ Trade Winds:
a. From 0 to 30 degrees latitude
b. Winds flows from eat to west
c. Warmer ear rises from equator to pole
4. Inter tropical Convergence Zone
99. **Intertropical Convergence Zone (ITCZ)
An area near the equator where the easterly trade winds of both hemispheres
converge producing a narrow band of clouds and thunderstorms.
**Doldrums:
An area near the Equator where there was little or no wind. (pacific and Atlantic
Occean)
**Horse Latitude:
Regions located at about 30 degrees north and south of the equator. These
latitudes are characterized by calm winds
100. Circulation Cells:
Hadley cells, 0-30° latitude
• Solar heating at the equator warms the air above, thus rises creating low pressure.
• The air travels to around 30°, cooling as it moves.
• At around 30° the cooled air sinks back to Earth to create an area of high pressure.
• Air moves from this high-pressure area to the equatorial low-pressure area.
• This is a thermally direct cell.
Ferrel cells, 60-30° latitude
• The Ferrel cells are found between the Hadley and Polar cells.
• Cold air sinks near 30° and rises near 60°. The air at the Earth's surface flows northwards and is
affected by the Coriolis force.
• The Ferrel cell is thermally indirect.
Polar cells, 60-90° latitude
• The air above the poles is cold, thus sinks creating high pressures
• The air moves towards the equatorial low-pressure zone, and warms up when meets the land
or ocean.
• At around 60° this warmed air rises.
• This is another thermally direct cell.
https://sites.google.com/site/gitakrishnareach/home/global-wind-
patterns?tmpl=%2Fsystem%2Fapp%2Ftemplates%2Fprint%2F&showPrintDialog=1
101. • Pressure: Force per unit area
Air pressure: The weight of the column of air above a particular location, per
unit area.
Pressure depends on:
a. elevation or altitude (higher up means less air above) (inverse Relation)
b. Air Composition (Air with a large amount of water vapor is less dense than
dry air because the water molecule has less mass than either an individual
nitrogen or oxygen molecule) (Direct Relation)
c. The average temperature (hot air is lighter than cold air) (Inverse Relation)
102. GLOBAL PRESSURE PATTERN
1. Equatorial Low Pressure Belts/ Doldrums
It lies at the Equator/ Doldrum
Warm air from the equator rises- Little or No winds
2. Tropic High Pressure Belts/ Horse Latitude
30-35 degree North- Calm Winds
3. Sub-polar Low Pressure Belts:
At about 60 degree North and South of Equator.
Pressure is low.
4. Polar High Pressure Belts:
At about 70 to 90 degree North and South of Equator
The cold descending air gives rise to high pressures
over the Poles
Atmospheric pressure is the weight of the column of air at any given place and time. It
is measured by means of an instrument called barometer.
https://www.pmfias.com/pressure-belts-pressure-systems-equatorial-low-sub-tropical-high-sub-polar-
low-polar-high/#ib-toc-anchor-7
103. WEATHER VARIABLES
• Temperature: Prevailing temperature condition in all parts of the world
• Pressure: The weight of the column of air above a particular location, per
unit area.
• Circulation: The movement of sth around a certain route
• Precipitation: Anything that falls after the condensation of atmospheric
water vapours under gravity.
• Humidity: The concentration of water vapors in the air over a certain
surface area
104. STORMS, CYCLONES, HURRICANES, TYPHOONS
A large scale closed circulation system in the atmosphere which combines low
pressure and strong winds that rotate counter clockwise in the northern
hemisphere and clockwise in the southern hemisphere.
They are characterized by:
a. Low atmospheric pressure at the core of the storm
b. Strong winds that are caused by the pressure difference
Storms, Cyclones, Hurricanes, Typhoons, etc. are the terms used for the same
process; however, their names are based on where they happens- location
Eg.
East and West USA = Hurricanes
West North Pacific-Japan, Philippines, China = Typhoons
West South Pacific and Indian Occeans = Cyclones
Australia= Willy Willies There are Two different types of surface-based
cyclones
1. Extra-tropical Cyclones/ Mid Latitudes
Cyclones
2. Tropical Cyclones
105. CYCLONES/ TROPICAL CYCLONES
A Cyclone is a weather phenomenon that is essentially a rapidly rotating storm
system with characteristics such as a low-pressure center, strong winds and
thunderstorms that produce heavy rain.
Formation and anatomy of Tropical Cyclones:
• Tropical cyclones form only over warm ocean waters near the equator- Direct sun
heat.
• As the temperature increases the air blows up leaving behind low pressure core.
• Consequently, it causes the air from surrounding areas with higher pressure to
move towards the low-pressure area which further leads to warming up of the air
and causes it to rise above.
• As the warm, moist air rises and cools the water in the air forms clouds
• The complete system of clouds and wind spins and grows, along with the ocean's
heat and water evaporating from the ocean surface.
• As the wind system rotates with increasing speed, an eye gets formed in the
middle
• The eyewall is the region of a cyclone that surrounds the eye. It is the most
destructive part of the storm as heavy rainfall, extreme winds and very
dense clouds-rain bands- driven from the eye, create intense conditions for any
type of environment.
106.
107. Causes of Tropical Cyclones:/ conditions
Here are the factors responsible for cyclone formation:
• Warm temperature at sea surfaces.
• Coriolis force impact area that forms a low-pressure zone.
• Atmospheric instability.
• Increased humidity in the lower to middle levels of the troposphere.
• Pre-existing low-level disturbance or focus.
108. Impacts of Tropical Cyclones:
Cyclones are often accompanied by strong winds, torrential rains and storm
surge.
These three elements cause have to a great extent as follows:
• Strong winds cause damages to infrastructure, uproots trees, and lead to
other catastrophes.
• Torrential rainfall leads to unprecedented floods and damages to houses and
buildings.
• Due to storm surge, seawater levels rise, and the coastal areas are exposed to
floods.
• The rise in seawater level also erodes beaches and embankments.
• Severe cyclonic storms resulting in floods can damage vegetation and
livestock.
• Due to the strong winds and flood conditions, the soil becomes infertile.
• Results in the loss of human, plant and animal lives
• Affect the country's economy.
109. Categories of tropical Cyclones:
The intensity of a tropical cyclone is defined by five different categories;
the higher the category, the greater the severity of the cyclone.
Although developed in the USA, tropical cyclones around the world are measured by the Saffir-
Simpson Hurricane Wind Scale which originated from 1971 with Herbert Saffir, a civil engineer
and Bob Simpson of the US National Hurricane Center.
Categories Wind Speed Damage Surge Surface
Catg. 1 74-95 mph Minimal 4-5 feet
Catg. 2 96-110 mph Moderate 6-8 feet
Catg. 3 111-130 mph Extensive 9-12 feet
Catg. 4 131-155 mph Extreme 13-18 feet
Catg. 5 >155 mph Catastrophic 19+ feet
Examples:
https://www.worlddata.info/asia/pakistan/cyclones.php
110. Preventive measures to combat Cyclones
Following steps can be helpful to stay safe during cyclones -
• It is necessary to stay indoors during a cyclonic storm and keep away
from electrical mains.
• In extreme situations, one must prepare an emergency kit that is
essential for survival.
• In case your house is unsafe, it is advisable to shift before the onset of a
cyclone.
111. MIDLATITUDE CYCLONES:/ Extratropical Cyclones
• The mid latitude cyclone is the dominant weather system in middle and high
latitudes.
• It is a large in-spiraling of air that repeatedly forms, intensifies, and dissolves along
the polar front.
• They occur in areas that are between latitudes 30° – 60° from the equator.
• They are not the same as Tropical Cyclones.
• These are actually many masses of cold and warm fronts
producing rain, heavy wind, tornadoes and even hails.
112. Formation of MIDLATITUDE CYCLONES:
1. Along the polar front, two very different air masses are in contact. The airflows
converge from opposite directions, setting up an unstable situation.
1. An disturbance begins, cold air is turned in a southerly direction, and warm air in a
northerly direction, creating a cold front and a warm front. As the fronts begin to
move, the precipitation process begins.
1. The disturbance along the cold and warm fronts deepens and intensifies.
Precipitation zones along the two fronts are now strongly developed.
1. The faster-moving cold front overtakes the warm front, lifting the warm, moist air
mass at the center completely off the ground because the warm air is shut off from
the ground, this is called an occluded front.
1. Eventually, the polar front is reestablished, but a pool of warm, moist air remains
aloft and north of the polar front. As its moisture content reduces, precipitation dries
out, and the clouds gradually dissolve.
113.
114. TORNADOES
A small but intense vortex of rising air associated with the strong updraft of an
intense thunderstorm.
Incidence: All year, forming particularly in late spring and summer
Tornadoes in Pakistan:
1981: killed 56 people
1985: killed 18 people
2001: killed 10 people
Wind Shear: variation in wind velocity occurring along a direction at right angles to the wind's
direction
Main Factor: Wind Shear
115. Formation of Tornadoes:
The formation and life cycle of tornadoes can be explained in a series of stages:
1. Storm development:
• Sunshine heats the ground and localized pockets of air become warmer than surroundings
• Where these warm bubbles of air (thermals) rise to sufficient height, shallow cumulus clouds
develop (dense, towering vertical cloud, typically forming from water vapor)
• If the temperature in the surrounding atmosphere decreases rapidly with warm bubbles may
rise to much greater heights, resulting in the up draughts and associated deep cumulus and
cumulonimbus clouds- thunder clouds
2. Storm organization:
• When the above process occurs in an environment where winds increase strongly with
height-strong vertical wind shear- the thunderstorm updraught may begin to rotate.
• The rolling motion becomes vertical. Thunderstorms that exhibit persistent and deep rotation
are called 'supercells'.
3. Tornado formation:
• Downdraughts within the storm help to concentrate the rotation & to bring it lower.
• Eventually the rotation may become so strongly-focused that a narrow column of violently
rotating air forms. If this violently-rotating column of air reaches the ground a tornado is born.
• The tornado is often visible because of the presence of a condensation funnel shaped cloud
which forms due to the much-reduced pressure within the tornado vortex.
• Dust and other debris lofted by the intense winds can also help to make the tornado visible.
4. Tornado dissipation:
• Cold downdraughts eventually wrap around the tornado, cutting off the supply of warm air.
The tornado typically narrows during this stage, and eventually the vortex dissipates.
116.
117. Effects of tornado:
Devastation from these tornadoes is often complete within the narrow limits of their paths. The Enhanced
Fujita intensity scale is a scale generally used to measure the intensity of tornadoes’ destruction based on
their speed. It can be classified as:
Damage Intensity Speed of tornado
Damages
Light Damage (65–85 mi/hr) Chimneys are damaged, tree branches are broken, shallow-
rooted trees are toppled.
Moderate damage (86–110 mi/hr) Roof surfaces are peeled off, some tree trunks are broken,
garages and trailer homes are destroyed.
Considerable damage (111–135 mi/hr) Roofs are damaged, trailer homes and outbuildings are
destroyed, large trees are uprooted or snapped
Severe damage (136–165 mi/hr) Roofs and walls are torn from structures, small buildings are
destroyed, non-reinforced masonry buildings are destroyed,
forest are uprooted
Devastating damage (166–200 mi/hr) Homes are destroyed, cars are blown some distance, and
debris includes large objects.
Incredible damage (>200 mi/hr) Strong homes are lifted from foundations, concrete structures
are damaged, damage from debris the size of automobiles,
trees are debarked
118.
119. DISASTER RISK MANAGEMENT:
NATIONAL DISASTER MANAGEMENT AUTHORITY (NDMA)
PAKISTAN FIRST NATIONAL DISASTER AWARENESS DAY: 08 OCT. 2017
• 5 DEADLIEST TROPICAL CYCLONES IN THE WORLD/ PK
• 5 DEADLIEST EARTHQUAKES IN THE WORLD/ PAKISTAN
• 5 DEADLIEST TSUNAMIS IN THE WORLD/ PAKISTAN
• 5 MAJOR FLOODS IN THE WORLD/ PAKISTAN
• 5 MAJOR TORNADOES IN THE WORLD/ PAKISTAN
• 5 MAJOR VOLCANOES IN THE WORLD/ PAKISTAN
https://pakistanweatherportal.com/?s=flood
