THE MANTLE
◇ It forms about 83 per cent of the earth’s volume and holds 67% of the earth’s mass.
◇ It extends from Moho’s discontinuity to a depth of 2,900 km.
◇ The density of the upper mantle varies between 2.9 g/cm3 and 3.3 g/cm3.
◇ The lower mantle extends beyond the asthenosphere. It is in a solid state.
◇ The density ranges from 3.3 g/cm3 to 5.7 g/cm3 in the lower mantle.
◇ The mantle is composed of silicate rocks that are rich in iron.
◇ Regarding its constituent elements, the mantle is made up of 45% oxygen, 21% silicon, and 23% magnesium (OSM).
◇ Temperatures range from approximately 200 °C at the upper boundary with the crust to approximately 4,000 °C at the core-mantle boundary.
◇ Because of the temperature difference, there is a convective material circulation in the mantle (although solid, the high temperatures within the mantle cause the silicate material to be sufficiently ductile).
