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1. EARTH AND ITS FEATURES

2.  The mean distance of the Earth from Sun is
computed as 149,642,000 k.m. this distance
commonly referred as one Astronomical unit.
 It is easy to describe the distance of other
planet from sun.i.e

3. name Distance (A.U)
Mercury 0.39
Venus 0.72
Earth 1.0
Mars 1.52
Jupiter 5.20
Saturn 9.54
Uranus 19.20
Neptune 30.10
Pluto 38.0

4.  Earth revolve around the sun along regular,
stable and nearly circular path called orbit.
 The revolving speed of earth is of 29.76
km/s and complete one revolution in 365.25
days or one year.
 Planet also rotate about their axis and earth
take 23 hours 56 minutes and 4 seconds for
one rotation about axis.

5.  Earth is commonly described as a spheroid.
 Earth has an equatorial diameter of
12757.776 km and a polar diameter of
12713.824 km thus showing a difference of
43.952 km.
 Earth shows an equatorial bulge and
flattening at the poles.
 Earth mean density is of 5.517 gm/cm cube
 Earth volume= 1.08* ten power 27 cc
 Mass of earth = 5.975* ten power 27 g.

6. ATMOSPHERE
 The outer gaseous part of the earth starting
from the surface and extending as far as 700
km and even beyond is termed atmosphere.
 It has 1-million part of the total mass of the
earth. This gaseous envelop , is held around
the earth due to its gravitational pull.
 Atmosphere has layer structure and different
layers are distinguished on a number of
basis:

7. 1. Change in composition
2. Change in temperature
3. Degree of ionization
 Chemically , the atmosphere is made up of a
mechanical mixture of gasses commonly called
air.
 Chemical composition of air
Component Value percentage
Nitrogen 78.084
Oxygen 20.946
Argon 00.934
Carbon dioxide 00.033
Others (Ne , He, Kr, Xe etc.) 00.033

8.  This composition is uniform up to 80 km from
earth surface and is called homosphere to
differentiate the overlying part that forms the
heterosphere.
 Thermally or on the basis of temperature
atmosphere is classified as –
 Troposphere, stratosphere, mesosphere and
thermosphere.

9. THE TROPOSPHERE –
 it start from earth surface to an average
height of 11 km.
 Its upper boundary called tropopause lies at
about 9 km above the poles and 18 km
above the equator.
 It contains almost 9/10 of total mass of
atmosphere. It is this layer of gases that is
responsible for most of the weather forming
process on the earth.

10.  In this layer there is a regular fall in
temperature at a lapse rate of 6.3 ºc/km up to
tropopause and having temperature at that
height is of -40ºc to -60ºc.
 The most important character of troposphere
is occurrence of a strong turbulence and
thorough mixing of the gases in this layer.

11. STRATOSPERE
 This is 2nd layer of atmosphere starting from
tropopause and up to an average height of
50 km. it differs from the lower layers in
following respect –
1. Temp. constant- 20 km then start
decreasing.
2. It contains almost entire ozone gas and
known as ozone layer.
3. It, itself has layer structures.

12.  Ozone layer- 9km to 35 km from earth
surface.
 Maximum concentration of ozone- 20-25 km.
 Best quality of ozone layer- capacity to
absorb a good proportion of solar radiation
including u-v rays coming from sun.
Mesosphere –
It is 3rd zone of atmos. Which begins from
50km to a height of 80km from earth surface.

13. THERMOSPHERE
 The 4th and last zone of atmos. It start from
80 km and extends up to 500km.
 In temp. rising and reaches 1000ºc & above
 This zone is very rarefied in nature, the
individual gas particles being separated by
considerable distances. It is the solar
radiation at these heights that is most
dangerous.

14. I0NOSPHERE
 It start from 80 km to variable heights. Gases
in this layer absorb solar radiation from sun
and bcz of this gases break up into ions.
 Ionosphere has proved a boon for long
distance radio communication by virtue of its
property of reflecting long radio waves.
 Beyond 700 km is exosphere with minimum
atomic collusions.

15. LITHOSPHERE
 It is the stony part of the earth and in broader
sense includes all the solid materials
composing the earth from surface
downwards.
 The body of earth is subdivided in three
specific layers or zone that is-
 Crust
 Mantle
 Core

16.  The uppermost solid shell of the earth is
called crust.
 Mantle is that zone within the earth that
starts from M-discontinuity and continue up
to a depth of 2900 km.
 The 3rd and innermost structural shell of the
earth that starts at a depth of 2900 km and
extends up to centre of the earth.

17. THE HYDROSPHERE
 Collective name for all natural water bodies
on or below of earth surface.
 It makes 0.03% of mass of the earth.
 98% of hydrosphere is saline water present
in seas and oceans water.
 Seas and bays together cover 70% of earth
surface.
 Rivers & lakes spread over hundred or
thousand square km

18.  Ice and snow are 3rd major part of
hydrosphere.
 Water in the pores of rock called
groundwater.
 On the basis of present state of knowledge, it
can be said that this zone is a feature unique
to our planet only.
 Water has 3 forms gaseous , liquid and solid.

19. BIOSPHERE
 This term is somewhat used to express the
collective life form, as it exists on the surface
and under water.
 This zone has also been responsible for
many geological processes that have been
going on the planet since the evolution of life.