KALYAN SIR_ THE EARTH.pdf

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8/14/2014 KALYAN SIR: THE EARTH

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THE EARTH

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THE EARTH

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http://www.kalyansir.net/2014/02/the-earth.html 2

Origin of Earth

Hypothesis of origin of Earth

The age of earth

The shape of earth

Rotation

Revolution

The axis of earth

Latitudes

Longitudes

Tropic of Cancer

Tropic of Capricorn

Arctic circle

Antarctic Circle

Standard Time

The structure of the earth

ORIGIN OF THE EARTH

The most common belief is that the earth has been originated from the Sun. Some

scholars propounded theories regarding the origin of the earth.

Kant - Gaseous Hypothesis


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Laplace - Nebular Hypothesis(Nebula means Cloud)Jeans and Jeffrey - Tidal HypothesisRussell - Binary Star HypothesisHoyle - Supernova HypothesisOtto Schmidt - Inter stellar DustHypothesis

Continental Drift theory:

Abraham Ortelius (Dutch) was the first to propound this theory in the year 1596.

Antonio Pellegrini was the second to propound the theory.

And finally the Continental Drift theory was proposed by Alfred Wegener (Germany)

in the year 1912).

According to this theory:

1. About 150 million years ago there was only one continent in the World called Pangea.

2. The Pangeawas surrounded by a mega Oceancalled Panthalassa.

1. Around 200 million years ago pangea broke into Laurasia (North) and Gondwanaland(South).

PLATE TECTNOIC THEORY:

The Plate tectonic theory was propounded by McKenzie, parker and Morgan in the year

1967.

According to this theory the outermost part of the earth is made up of Lithosphere

(Crust + uppermost part of the mantle).

Below Lithosphere it is Asthenosphere (inner part of the upper mantle).

The Asthenosphere behaves like superheated material over which the Lithosphere floats.


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These are also called Lithosphere plates.

According to this theory Earthquakes, Volcanoes, mountain building and oceanic trench

formation occur.

THE BIG BANG THEORY

The Big Bang Theory was propounded during 1950s and 1960s.

This theory was validated in the year 1972.

According to this theory everything in the universe emerged from a point known

as Singularity.

AGE OF THE EARTH:

The solid crust of the earth came into existence about 4.6 billion years.

How do you estimate the age of the rocks that forms into the earths crust? It is through

radio carbon dating.

The radio carbon dating technique was developed by Willard Libby (USA, 1908

1980).

Radio carbon dating is also called carbon dating.

THE SHAPE OF THE EARTH:

Just like any other object the earth has got a shape.


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The shape of the earth is called Geoid. It means earth-shaped.

The real form of the earth resembles a sphere. That is compressed at the poles and

slightly bulges at the equator.

This is also known as oblate ellipsoid or spheroid.

The bulge at the equator is because of the rotation of the earth.

The earth moves in space in two distinct ways.

v Rotation

v Revolution

(Note:Be clear with rotation and revolution. If it is not clear please read again immediately,kindly do not leave and jump to other area).

ROTATION:

The rotation is the movement of earth on its own axis. (Around its own self).

SHAPE OF THE EARTH
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The earth rotates on its own axis.

The earth moves in the West to East direction. (Not East to West)

The total time taken by the earth for rotation is 23 hours 56 Minutes and 4.09 seconds.

The rotation of the earth causes the formation of day and night.

REVOLUTION:

The revolution is the movement of the earth round the Sun.

ROTATION OF THE EARTH
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The total time taken for revolution is 365 days. (365 days 6 hours 9 minutes and 9.54

seconds).

The revolution causes the seasons.

Please Read this:

(Did you observe that there is an additional 1/4th day? Wenormally say that there are 365 days in a year. What happened tothe 1/4th day?

Do you know what a leap year is? This is a year with 366 dayswith 29 days in February. This happens every 4 years.

Where from it is coming? The additional 1/4thday is taken for 4years and it becomes 1 day and it is added to the year.

Hope It is clear. If not read again, once you understood pleaseexplain the same to your friend, brother or sister. It improves yourquality of understanding)

REVOLUTION OF THE EARTH
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Quick Review:

What causes day and night?

a. Rotation of the earth b. Revolution of the

earth (Answer: A)

What is responsible for change of seasons?a. Rotation of the earth b. Revolution of the

earth (Answer: B)

THE AXIS OF THE EARTH

The axis of the earth is ecliptic.

It is also called obliquity of the ecliptic.

AXIS OF THE EARTH
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The earth has an axial tilt of 23.40.

This axis remains tilted in the same direction towards the stars throughout the year.

This is the main cause of seasons.

This is also the cause for varying lengths of days and nights.

The Sun is vertically over the head of the equator on March 21st and September 23rd

every year. These two days are called equinoxes. (Equal day and night).

On June 21st the Sun is vertically overhead at the Tropic of Cancer (23 0N). This is

called Summer Solstice. During this time the Northern hemisphere will have longest day

and shortest night.

On December 22ndthe sun is vertically overhead of Tropic of Capricorn (23 0 S). This is

called Winter Solstice. The southern hemisphere will have longest day and shortest night.

LATITUDES: (Horizontal lines)

Latitudes are the imaginary lines on the surface of the earth.

LATITUDES
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These are the horizontal lines from East to West on the Surface of the earth.

This is the angular distance of a point on the earths surface measured in degrees from the

centre of the earth. (North or South).

There are 180 latitudes. 90 in the Northern hemisphere and 90 in the southern hemisphere.

The latitudes are also called parallels.

The each line of latitude is a circle.

The lines of latitudes also known as circles of latitudes.

The central line is called equator.

Among the parallels only equator is the great circle. (

What is a great circle? A great circle is a circle on the surface of the earth that passes

through the centre of the earth).

Reaming parallels are small circles.

The equator has the latitude of 00.

The equator divided the earth into Northern and Southern hemispheres.

EQUATOR
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Equator passes through Ecuador, Colombia, Brazil, Gabon, Congo, Uganda, Kenya,

Somalia and Indonesia.

The North Pole has the latitude of 90 0N.

The South Pole has the latitude of 90 0S.

LONGITUDES:(Vertical lines)

Longitudes are the imaginary lines on the surface of the earth.

These are the vertical lines from North to South on the surface of the earth.

This is the angular distance measured in degrees along the equator.

These are also called meridians.

One of these is called Prime Meridian that passes through the Royal observatory,

Greenwich, England.

LONGITUDES
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The Prime meridian is the 00longitude.

The prime meridian divides the earth into Eastern hemisphere and the Western

hemispheres.

There are 360 longitudes.

There are 180 longitudes in the eastern hemisphere and the other 180 in the western

hemisphere.

All the longitudes converge at poles.

The longitude that is exactly opposite to the Prime meridian is the International Date Line.

TROPIC OF CANCER:

This is a parallel.

This is at 23 0N of the equator.

This is also known as the Northern Circle.

TROPIC OF CAPRICORN:

This is a parallel.

This is at 23 0S of the equator.

This is also known as the Southern circle.

ARCTIC CIRCLE

This is a parallel.


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This is at 66 0N.

ANTARCTIC CIRCLE

This is a parallel.

This is at 66 0S.

Please Remember:

Equator (Horizontal line): 00.

Tropic of Cancer: 23 0N

Arctic Circle: 66 0N

North Pole: 90 0N

Tropic of Capricorn: 23 0S

Antarctic Circle: 66 0S

South Pole: 90 0S

Prime Meridian (Vertical line) : 00

International Date Line: 1800

STANDARD TIME:

Kindly read:

v The earth rotates 360 in about 24 hours, which means 15 an

hour or 1 in four minutes. Thus, when it is 12 noon at


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Greenwich, the time at 15 east of Greenwich will be 15 4 =

60 minutes, i.e., 1 hour ahead of Greenwich Time, which

means 1 p.m. But at 15 west of Greenwich, the time will be

behind Greenwich time by one hour, i.e., it will be 11.00 a.m.

Similarly, at 180, it will be midnight when it is 12 noon at

Greenwich.

We know what the time is.

We also know that the time is not same on all parts of the earth.

It varies from place to place.

This is because for the sake of convince the whole World is divided into 24 standardtime zones.

Each zone is separated by 150longitudes.

Or

By one hour.

Or

By 40 for 1 minute

Larger countries (greater east to west stretch) have more than 1 time zone.

Russia has 11 time zones. (Area wise Russia is the largest country).

USA has 6 time zones.

Canada has 5 time zones.

Do you know how many time zones are present in India?

1 Time Zone

Travelling from GMT towards east will gain time.


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There is a total difference of 24 hours between the two sides of 1800meridian.

At the International Date Line the date changes exactly by 1 day when it is crosses.

The International Date Line passes through Bering Strait(Between USA and Russia),

Fiji, Tonga and other islands.

(What is a Strait? Strait is a narrow strip of water connecting two larger bodies of

water).

Give me Quick Answers:

1. The country with highest number of Time Zones

is

a. USA b. Russia c.

India (Answer: B)

2. The country with only one time zone.

a. USA b. Russia c.India (Answer: C)

3. How many degrees that the earth rotates in 1

hour

a. 3600 b. 1800 c. 150

(Answer: C)


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THE STRUCTURE OF THE EARTH

The interior structure of the earth is divided into

The Crust

Mohorovicic discontinuity

(Moho) The Upper Mantle

The Mantle

Gutenberg discontinuity

The Outer Core

Lehmann discontinuity

The Inner Core

The Crust, the Mantle and the Core are the layers in the earth.

The uppermost mantle along with the crust is called Lithosphere.

The basis of differentiation of these layers is the density of the rocks in different parts.

The Mohorovicic discontinuity, the Gutenberg discontinuity and the Lehman discontinuity

are the transitional zones.

STRUCTURE OF THE EARTH
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Let us discuss about these layers in detail.

THE CRUST:

This is the topmost layer of the earth.

This is the thinnest layer of the earth.

This layer has the least density.

The thickness of this layer varies from 8 to 40 km.

The lower limit of the crust is identified by the transitional zone called Mohorovicic

discontinuity.

The Crust is the most important part of the earth for human beings.

The Oceans and the continents are situated on the crust.

The thickness of the crust is less under the oceans.

The thickness of the crust is more under continents.

The thickness of the crust under the mountains is much more.

The Crust is rich with the minerals like Silica and Aluminum.

The crust is also called Sial. (Please remember this).

What is Sial? (Si - Silica and Al - Aluminum).

Oxygen is the most important constituent of this layer.

Oxygen constitutes about 46.6 percent.

The other important constituents are Silicon, Aluminum, Iron, Calcium, Sodium etc.


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The Basalt rock is available in the oceanic crust.

The Granite rock is available in the continental crust.

THE MANTLE:

This is the intermediate layer of the earth.

The mantle is about 2895 km thick.

This is the thickest layer of the earth.

The minerals that are present in this layer are in semi solid state.

The mantle is also called Sima.

What is Sima? (Si Silica and Ma Magnesium).

The Gutenberg discontinuity is the transitional zone that separates the Mantle and the

core.

THE CORE:

This is the innermost layer of the earth.

The radius is about 3475 km.

The innermost part of the core is crystalline.

The core is the densest part of the earth.

The inner core was discovered by Lehmann in the year 1936.

The temperature of the core is between 22000and 27500 C.


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