Question

Q. Consider the following statements with reference to interior of earth

1. The primary source of Earth's heat is the combination of Extraterrestrial impacts, gravitational energy and radioactivity.
2. The lithosphere which is the outer layer of earth's crust comprises both continents made of granite rocks and oceans made of basaltic rocks.
3. The density of basaltic rocks is more than granitic rocks and because of this the sial is lighter than sima.

Which of the above statements is/are correct?

• A.
  1 only
• B.
  1 and 3 only
• C.
  2 and 3 only
• D.
  1, 2 and 3

Answer 1

The correct option is D

1, 2 and 3
Explanation:

There are three main sources of heat in the deep earth:
All the statements are correct - There are three main sources of heat in the deep earth: (1) heat from when the planet formed and accreted, which has not yet been lost; (2) frictional heating, caused by denser core material sinking to the center of the planet; and (3) heat from the decay of radioactive elements.

The outer layer is the earth crust –the lithosphere consists of 2 parts – the upper part consists of granitic rocks and forms the continents which comprises silica and alumina which have a density of 2.7.

The lower part consists of basaltic rocks and forms the oceans which comprises of silica,iron and magnesium which has average density of 3.0