Page 142 - SST Class 07

than ever is being trapped underneath these in the atmosphere. This is the reason why there is
gases and the earth overall is warming. This is such a concern about the thinning of the ozone
termed as the Greenhouse Effect. layer and its depletion.

Ozone is a small, but very important component If it is unable to filter out harmful rays, then more
of the atmosphere. Ozone is made up of three UV radiation reaches us. This is a major issue
oxygen molecules and is what protects us from because UV radiation makes us very sick. It
harmful UV (ultraviolet) radiation of the sun. causes skin cancer (leukoderma) and harms
Ozone absorbs this radiation, blocking most of it other plants and animals and sometimes dangers
from reaching us on the ground. It acts as a filter of vision impairment.

Co and other gases in the atmosphere
2
trap heat, keeping the earth warm
Long
Wavelength

Short
Wavelength

The Greenhouse Effect

Terminology

Exosphere : the outermost region of a planet's atmosphere
Meteorites : a piece of rock or metal that has fallen to the earth’s surface from outer space as a meteor
Nimbostratus : cloud forming a thick uniform grey layer at low altitude, from which rain or snow often falls
Insolation : exposure to the sun’s rays
Interplanetary : situated or travelling between planets

Inside Story
Inside Story
g The earth is huge spherical ball slightly tilted on its axis, third in position from the sun in the
Solar System.
g The radius of the earth is roughly about 6400 kms.
g The higher we are above the earth’s surface, the colder it gets.
g The temperature in the stratosphere gets warmer as we go up due to the absorption of
ultraviolet radiation in the ozone layer.
g The atmosphere also has water vapour which is sometimes as high as 5% of the
atmosphere in the wettest places.
g The average weather condition of a place for a longer period is called the climate of that
place.
g At a given temperature, the capacity of air to hold moisture is limited.

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