The earth is 4600 million years old. modern man has lived on
PEOPLE and PLANET EARTH
The earth is 4600 million years old. modern man has lived on the earth for only 35000 years but in that time we have changed our planet in many ways . many of the things that we have done are good but many many more are not good for the earth .
In big cities cars and buses have polluted the air . many people in cities now have very bad health problems.
Factories have also polluted the land and the water . as a result many rivers and lakes are now dead .
The ozone layer
Around the earth there is a special type of oxygen called ozone(o3) ozone is important because it stops ultraviolet radiation from the sun . many aerosol sprays and factories destroy ozone and they have made a very big hole in the ozone layer . this means that too much ultraviolet radiation now enters earth . this is very dangerous because it can cause cancer .