what you are known about above the earth?


Atmosphere

Structure of the atmosphere




Atmosphere – the air which envelopes the earth and extends up to a considerable height from the surface of the earth is called the atmosphere. it consists of a mixture of various gases and is held to the earth by gravitational attraction. This envelopes of air is densest at sea level and thin rapidly upwards. the atmosphere constitutes a very insignificant % of the mass of the earth.

Structure of atmosphere – the structure of the atmosphere consists of the five basic layers   -

the layer of the atmosphere
A – the troposphere

B – the stratosphere

C – the mesosphere

D – the ionosphere

E –the magnetosphere and exosphere

The troposphere – it is the densest layer of the atmosphere and contains approximately 75% of the mass of the atmosphere and almost all the water vapor and aerosol.

the troposphere extends from the Earth surface up to the tropopause where the stratosphere begins
the gift of the troposphere is greatest in the tropics about 17 km and smallest at the poles about 8 kilometer

the lower part where friction on the Earth's surface influences with air flow is the planetary boundary layer or peplosphere which is 2 kilometers deep on average, depended on the landform and which is separated from the rest of the troposphere by the capping inversion layer.

the temperature of air in the troposphere decrease at the rate of 1 Degree Celsius per 165 M of height
stratosphere – here the air is at rest. it is an isothermal region and is free of cloud, dust and water vapor it extends up to a height of about 50 kM .its upper stata is rich in Ozone which prevents ultraviolet radiation by obsorbing them and a very little is filtered through it which does not harm living organisms

Mesosphere -- it is a very cold region and extends up to a height of 80 km from the surface of the earth. at a height of 60 km there is an intermediate layer which is known as radio waves obserbing layer.

Ionosphere -- it is a region of electrically charged or ionised air lying next to mesosphere. it products from falling meteorides . it extends up to a height of 150 km.


Exosphere -- it is the upper most region of the ionosphere and is fringe of the atmosphere. Its  boundary or not  known

Composition of the atmosphere -- the atmospheric composition of the troposphere reveals to major  constituents:  molecular nitrogen and Molecular oxygen, the minor constituent include carbon dioxide , water vapour and inner inert gases. the water vapour is concentrated in the lower part of the atmosphere the composition of the atmosphere is as follows :

                        Nitrogen                                          78.09 (volume_%)
                        Oxygen                                            20.97 (volume_%)
                     Carbon dioxide                                  0.03( volume_%)

the rest is made up of organ Helium Helium , neon , krypton  etc. water vapour is present in varying proportions over different parts of the Earth surface.

                                 The hydrosphere  

  it is an irregular but nearly continuous layer of salt and freshwater, making up to the oceans, seas, lakes ,rivers ,snow and ice on the surface and also the groundwater the world ocean cover about 71% of the Global surface and its average depth is about 3800 m.

The hydrosphere


Composition of sea water -- sea water is a solution of salt- a Brine -who's ingredients have maintained approxmentally proportions over a considerable span of geologic time. of the various elements combined in these salts chlorine alone makes up to 55% by weight of all the dissolved matter and sodium makes up to 31% .magnesium, calcium, Sulphur and potassium are the other four major elements in the salts. sea water also hold in solution in small amounts of all the gases of the atmosphere

   Common elements present in the Hydrosphere, ocean water as Brian Mason  is as follow .
                  Oxygen                          85.79 % (by weight)
                  Hydrogen                       10.67% (by weight)
                  Chlorine                           1.898% (by weight)
                    Sodium                           1.056% (by weight)
                    Magnesium                     0.127% (by weight)
                     Sulphur                          0.088  % (by weight)
                      Calcium                         0.040 % (by weight)
                     Potassium                       0.038% (by weight) 
                        Bromine                            0.007% (by weight)
                   Carbon(inorganic)              0.003% (by weight)
                    Strontium                          0.001% (by weight)
                                                                   
  he rest is made up by other dissolved gases.


                                                The lithosphere  -- 

it is the general term for the entire solid or realm,i.e., The crust according to the recent  concept the term lithosphere is used for the Crust and upper part of the mantle, which is considered to be elastically very strong lithosphere is underlain by  asthenosphere.


As per the estimation,  made by Clarke and Washingtpon, the listhosphere consists of 95% igneous rock , 4% shale, 0.75% sandstone and 0.25 % limestone( the metamorphic rocks been altered equivalent of one or other of these rocks).

Chemical composition of the lithosphere --  it has been observed that while the continents are distinctly sialic the ocean floor represent the upper sima are distinctly basic in nature. The following is the composition in terms of elements (by weight), as given by Clarke and Washington :


                 Oxygen             46.71                       sodium             2.75
             Silicon                   27.69                      potassium           2.08
          Aluminium               8.07                         magnesium          2.60
           Iron                     5.05                              titanium                 0.62
           Calcium                3.65                           hydrogen                  0.14
              Remaining     elements        0.64

In terms of oxides (by weight) the chemical composition of the lithosphere is as follows:

SiO2                         59.07                    silicon oxide
Al2O3                      15.22                     aluminium oxide
CaO                        5.10                         calcium oxide
FeO                         3.71                        ferrous  oxide
Na2O                     3.71                          sodium   oxide
MgO                   3.45                         magnesium oxide
K2O                     3.11                         potassium   oxide
Fe2O3                         3.10                           Ferric oxide
H2O                     1.30                               water
TiO2                     1.03                            titanium oxide
Remaining oxides      1.20

From the above, it is evident that 99% of the upper crust is made up of only 10 elements with oxygen accounting for slightly less than 98 % of the lithosphere with silica being the most abundant.

    The mineralogical composition of the lithosphere shows that plagioclase feldspar is the most abundant mineral and apatite is the least one. the estimate as given by Clarke and Washington is as follows:

Quartz                         11%          by volume
Alkali  feldspar            16 %              by  volume
Plagioclase feldspar (feldspar)                      47%
Amphibole and biotite                      20 %
Magnetite                                         5%
Apatite                                               1 %


The above analysis gives only the average mineralogical composition of the lithosphere but it does not in any way represent the composition of the earth as  a whole or even the crust as a whole.