Question

what is meant by sima and sial

Answer 1

About 71%of earth surface is covered with water, which appears blue from space.but also due to atmosphere land appears quite hazy, which at a distance becomes a wash with the predominantly blue surface.hence,earth is referred as'blue planet'.

hope it's helpful !!!

Answer 2

Sial is the upper layer of lithosphere which is made up of silica and aluminium.

Sima is the lower (inner)part of lithosphere which is made up of silica and magnesium.