Pg.no. 101
Lower Mantle
Temperature: 3,000°C
State: solid
Composition: iron, oxygen, silicon, magnesium and aluminium
The lower mantle is found between 670km and 2,890km below the surface, and is made
from solid rock. The rock is hot enough to melt, but is solid because of the pressure pushing
down on it.
Upper Mantle
Temperature: 1,400°C – 3,000°C
State: liquid / solid
Composition: iron, oxygen, silicon, magnesium and aluminium
This layer is up to 670km below the Earth’s surface. The lower part of the upper mantle is
made from both solid and melted rock (liquid), while the rock in the upper region is stiffer,
because it’s cooler.
Crust
Temperature: Around 22°C
State: Solid
Composition: Oceanic crust made up of iron, oxygen, silicon, magnesium and aluminium.
Continental crust made up of granite, sedimentary rocks and metamorphic rocks.
The Earth’s surface is covered by its thinnest layer, the crust. Land is made of continental
crust, which is 8km to 70km thick and made mostly from a rock called granite. The layer
beneath the ocean bed is made of oceanic crust, which is about 8km thick and made mainly
from a rock called basalt.