NCERT 6th Class (CBSE) Social Science: The Realms of the Earth

Question: Which two layers from the crust of the earth?

Answer: The crust is made up of two layers the upper layer is called sail and the lower layer is called sima has rocks rich in silicon and magnesium.

Question: What constitutes the hydrosphere?

Answer: The hydrosphere oceans, seas, rivers and lakes, frozen water in ice sheet, underground water and water and water vapor present in atmosphere.

Question: What are the main gasses found in atmosphere?

Answer: Above the surface there is an envelop of air that surrounds the earth. It is held in its place due to earth’s gravity. This envelop is called atmosphere.

Composition of the Atmosphere:

1. Nitrogen: 78 percent – it helps in the growth of living organisms.
2. Oxygen: 21 percent – It is the gas human beings breathe.
3. Hydrogen, Helium, Argon ozone and many other gases: 0. 97% -These are necessary for many reasons. For example, the ozone layer protects us form the harmful ultraviolet rays of the sun that can cause skin cancer.
4. Carbon dioxide: 0.03 per cent – Plants use it to make food: it also helps to keep the earth warm.

Question: What is global warming?

Answer: Loss of forest cover and pollution are believed to be the cause for global warming which is a serious – issue today.

Question: How does it affect our lives?

Answer: Excessive carbon emissions have have led to the rise in carbon dioxide in the atmosphere, resulting in a increase in global temperatures. It is causing climate-changes, which in turn are causing large scale devastation.