1. The endosphere
It is the interior of the Earth placed below the lithosphere (120 km thick).
According to geologists and geophysicists, the endospehre consists of concentric zones of increasing density toward the center. These zone are: the atmosphere (a), hydrosphere (b), the lithosphere (c) and
- The mantle or outer core (d) with 1,200 km thick and a density from 2.7 to 5 comprising feldspars.
- The middle core (e), with 1,700 km thick and a density from 5 to 9, formed by ferromagnesian silicates.
- The inner core (f) or NiFe, formed by nickel and iron of about 3400 km and an increasing density from 9 to 11, completely solid and greater stiffness than the steel.
In the middle core, rocks have a plasticity condition due to the high pressure and the high temperatures; pressure tends to solidify them and temperature tends to melt them. When the pressure decreases through a crevice in the lithosphere, the rocks melt and the pressure exerted by the gases causes the expulsion of those rocks as magma.
2. Choose one of these words: mantle, the middle core or the inner core: