Question

The crust and the upper part of the mantle together are known as :

• A. lithosphere
• B. asthenosphere
• C. mesosphere
• D. stratosphere

Answer 1

Answer:

A. lithosphere

Lithosphere

• The crust and the upper part of the mantle together are known as lithosphere.

• The part beneath the lithosphere, where the materials exist in the partially molten state is known as asthenosphere. This is the source of the molten rock material (lava) that comes out during volcanic eruptions.

• The lithospheric plates are situated above the asthenosphere which is in a semi plastic state. Magma, which is a part of the mantle remain molten due to the high temperature at the earth's interior and undergoes continuous convection.

• The plates move at a speed of 2 to 12 centimeters a year. The speed of this movement has not always been uniform. Studies indicate that the speed of the plate movement was up to 30 centimeters a year about 580 million years ago

• Alfred Wegener, a German meteorologist, put forward the idea of continental drift in 1912.