Environment and its Components

Posted on Oct 9 2019 - 6:54pm by Preeti

Environment and its Components

Definitions

Environment is a multi-dimensional systems of complex inter-relationships in a continuing stage of change.

It is in totality of all social, biological and physical or chemical individually as well as collectively that compose the nature and man made surroundings.

Environment is a holistic view of the world as it functions at any time, with a multitude of special elemental and socio-economic systems distinguished by quality and attributes of space and mode of behavior of biotic and abiotic forms.

It is the representation of physical components of the earth wherein man is the important factor influencing his environment.

Components/Segments of Environment

  1. Atmosphere
  2. Hydrosphere
  3. Lithosphere
  4. Biosphere

  1. Atmosphere
  • It is the blanket of gases surrounding the earth.
  • It extends to a height of about 2000 kilometers from earth’s surface.
  • The major components of atmosphere are nitrogen and oxygen, while minor components are argon, carbon dioxide and some trace gases.

Structure of Atmosphere

i. Troposphere

ii. Stratosphere

iii. Mesosphere

iv. Thermosphere

i.  Troposphere

  • 70% of atmosphere mass.
  • It lies from the surface of the earth to an altitude of 10 kilometers.
  • Density decreases with altitude.
  • The cold layer (56 degree C) at the top of troposphere, which shows a temperature inversion, that is a negative to positive lapse rate, is known as tropopause.
  • Lowest layer of atmosphere in which living organisms operate.
  • Strong air movements and cloud formations.
  • Consists of 78% nitrogen, 21 % oxygen, 1 % Argon, 0.03 % carbon dioxide, 0.0018 % Neon and 0.000524 % Helium, 0.0002 % methane and other gases such as krypton, nitrous oxide, hydrogen, xenon and ozone.
  • One of the most recent change in the troposphere involves the phenomenon of acid rains.
  • Most conventional aviation activity takes place in the troposphere, and it is the only layer that can be accessed by propeller-driven aircraft.

ii. Stratosphere

  • It extends between altitudes of 10 and 60 kilometers.
  • It is 50 km thick and contains a layer of sulphates which is important for the formation of rain.
  • It also contains a layer of ozone,which absorbs ultraviolet light known to cause cancer.
  • Ozone is formed form through a photo-chemical reaction where oxygen molecules splits to form atomic oxygen. The atomic oxygen combines with molecular oxygen and ozone is formed.

O2 + hv = 2O

O2 + O = O3

  • The stratopause separates the stratosphere from mesosphere.
  • The stratosphere is the highest layer that can be accessed by jet-powered aircraft.

iii. Mesosphere

  • It extends between altitudes of 60 and 100 kilometers.
  • In mesosphere the lapse rate is negative ( Lapse rate is decrease in temperature with altitude.)
  • The temperature reaches minimum of -95 degrees C The mesopause separates the mesosphere from the thermosphere.
  • The mesosphere is also the layer where most meteors burn up upon atmospheric entrance.
  • It is too high above Earth to be accessible to jet-powered aircraft and balloons, and too low to permit orbital spacecraft. The mesosphere is mainly accessed by sounding rockets  and rocket-powered aircraft.

iv. Thermosphere

  • It lies from an altitude of 100 kilometers upward upto 700 km.
  • Upper zone to thermosphere where ionization of O2 molecules occur is called ionosphere.
  • This layer is also called ionosphere.
  • Temperature increases with height.
  • The positive lapse rate raises the temperature to a  maximum of about 1200 degrees C.
  • Because the thermopause lies at the lower boundary of the exosphere it is also referred to as the exobase.
  • The layer is completely cloudless and free of water vapor.
  • The International Space Station orbits in this layer, between 350 and 420 km (220 and 260 mi).

Exosphere

  • The outer extremely rarefied fringe of the atmosphere is called exosphere which gradually merges with the outer space.
  • It extends from exobase which is located at the top of thermosphere at an altitude of about 700 km. to about 10,000 km.
  • This layer is cocmposed of mainly low densities of hydrogen, helium and several heavier molecules including nitrogen, oxygen and carbon dioxide closer to exobase.
  • The exosphere contains most of the satellites orbiting Earth.
  1. Hydrosphere

It covers  more than 75% of the earth’s surface either as oceans (salt water) or as fresh water. Hydrosphere includes sea, rivers, oceans, lakes, ponds, streams etc. Most of the earth’s surface water is in oceans, which contain about 35 parts per thousand of dissolved salt. The oceans are great reservoirs of water and they also regulate carbon dioxide. The oceans can absorb more carbon dioxide than the atmosphere. Of the remainder, most of fresh water with a salt content of 0.2 % is found either in lakes and ponds or in rivers and streams.

  1. Lithosphere

The solid component of the earth is called lithosphere, which includes mainly soil, earth’s rocks and mountains etc. It the mantle of rocks constituting the earth’s crust. The lithosphere mainly contains three layers-crust, mantle and outer and inner core. The surface of crust is covered with the soil which is rich in silica (Si) and aluminium (Al) and is also known as Sial layer. The continents belong to the Sial layer and are made of of granite rocks.

The next zone next to crust is rich in silica and magnesium (Mg). This layer is formed of basalt rocks and constitutes the ocean floors. The basal rocks are heavier than granite rocks. Next layer is the mantle which has a thickness of about 2400 km. The upper part of mantle is known as the Asthenosphere, while the lower mantle is called Mesosphere.

The inner most part of the earth is called core,which is rich in minerals like iron,nickle, cobalt mixed with Sulphur, ans silica. The thickness of the core extends to about 3500 km. The core consists of outer and inner core. The inner core is solid while the outer core is molten and metallic. The temperature of the core ranges between 5000 to 5500 degrees.

  1. Biosphere

It is composed of all living organisms and their interactions with the environment viz, atmosphere, lithosphere and hydrosphere. The planet earth alongwith its living organisms and environment (air, land and water) which sustains life is known as biosphere. The biosphere extends vertically into the atmosphere to about 10 km, downward into the ocean to a depth of about 35,000 ft and about 23,000 ft into the earth’s surface itself where life has existed.

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