Our Earth

 

OUR Earth

Introduction:

Our earth is the only planet known to have life. Life is possible due to its air, water and moderate temperature conditions. The earth consists of five deferent layered parts-atmosphere, hydrosphere, lithosphere, mantle and core. The atmospheres is a bulk of air, primarily of nitrogen and oxygen, and surround the surface consisting of the hydrosphere and lithosphere- the water and land massage respectively. Below them are the mantle and core, studying its rocks, scientists have inferred that the earth is about 4-5 billion years old. Various hypotheses have been propounded on have the earth was formed. The scientists have unraveled on how the earth was formed. The scientists have unraveled that the earth like other planets was formed out of the nebula, a disk-shaped mass of dust and gas left over from the formation of the sun. Since its birth the earth's surface has always been changing.

Shape and size

In the solar system, third from the sun, our earth ranks fifty among the eight planets in terms of their size. It is not perfectly round but elliptical in shape. Its equatorial region is spherical and poles are flat. The total mass of the earth is 5.97x 10²⁴ kg. It diameter is 12,756 km and the equatorial radius is 6,378 km.

Heat distribution

Distribution of heat differs on the earth primarily according to the distance from the equator. The amount of heat decrease as we move north or south from the equator. Equatorial regions are hot as they receive direct rays of the sun. it is very cold at poles because only slanting rays reach there. But the areas with moderate latitudes between the equator and poles receive moderate rays and remain mild. Climate is also influenced by altitude. Low-lying areas have dense air so absorb more heat than those at high altitude. Temperature decreases approximately by 1o per 165 m from the sea level. Distance from the sea affects the climate of a place. The coastal areas are mild while continental areas are extreme. The influence of these factors is not always balance. Though low-lying the Siberian plain is not hot because of its high latitudinal location (above 60 ^o N). Similarly though at equator, Quito in Ecuador is not hot because of its high altitude (2850 m). You will learn more about the effects on climate on the earth in grade X.

Inclination, motion and seasons

Because of its round shape, only a half of the earth gets the solar rays once. The earth's motion on its axis every twenty-four hours causes ration of days and nights on the two hemispheres. The earth is also inclined at an angle of 66.5⁰on its orbital plane. Due to such inclination the two hemispheres are at different distance from the sun. When one hemisphere is tilted towards the sun, the other is tilted always. Only the equator is always at the same distance. Such inclination brings about differences in length of such inclination brings about differences in length of sunshine hour and climate of the two hemispheres. You probably kwon the poles have a six-month day and a six-month night in a year.

 

The earth also moves on its orbit to go round the sun. The movement of the inclined earth on its elliptical orbit causes changes in seasons. Two opposite hemispheres experience two opposite seasons at a time. When it is summer in England, it is Australia and vice versa.

Life and ecosystem

The earth is the wonderful home of millions of plants and creatures with many types and features. Its moderate temperature, atmosphere and abundant water have made life possible. Varied landforms ad climate conditions have supported many biomes on the earth. An ecosystem has many habitat types which are linked by ecological processes. An ecosystem may be small, like the Himalayas or the Sahara desert, and the whole earth is one marvelous ecosystem sustaining life in a wonderful way. Many ecosystems have been undergoing damages causes by human activities.