Soils, Vegatation and Animals Questions and Answers - 2

Question: 6

What was the status of trees in Tamil Culture?

Sacred trees (thala vrikshas) are found in our sacred groves and in the tank or lake areas of the country. Every temple, temple town has a sacred trees. In some place, the trees are in the sanctum of temples and are worshipped along with the gods. Some cities are even named after the thala vrikshas.

Question: 7

Where do we find alluvial soils?

The alluvial soils are found in both the coastal and deltaic areas. They are found in the deltaic tracts of the rivers of Tamilnadu, more especially the Cauvery in Thanjavur, Thiruvarur and Nagapattinam districts and also in Villupuram, Cuddalore, Thirunelveli and Kanyakumari districts.

Question: 8

What are the ill effects of deforestation?

i. With the destruction of forests in the country, there is a destruction of 1.5 million hectares every year. They are in fact destroyed by human activities.

ii. Other causes account for 1 million hectares of land being destroyed every year.

iii. If the trees are felled indiscriminately, the humus and the plant nutrients of the soils will be removed easily by the rains.

iv. If there are no forests along the hill or mountain slopes, the flow of water by gravity will increase; it will cause floods.

v. Sediments will be brought down by the waters, causing damages to crops in the fields by their deposition.

vi. In course of time, the cultivated lands will become wastelands, unsuitable for any cultivation.

Question: 9

Write about the continental crust?

The continental crust is 20 to 70 kms thick. This crust is composed of 80 percent Silica and 15 percent Aluminum. The remaining 5 percent is composed of other rocks. This is also referred as SIAL layer which is derived from the first two letters of Silica and Aluminum.

Question: 10

Write a note on oceanic crust?

The oceanic crust is thin and measures between 5 to 10 kms thick. It is composed of 40 percent Silica, 40 percent Magnesiam and 20 percent Iron and other minerals. Hence this is refered as a SIMA, which is derived from the first two letters of Silica and Magnesium. The rocks in the SIMA belong to basaltic variety. They are heavy because of their high density.