Chemical and Mechanical
Layers of the Earth
6400 km (Earth’s radius)
Chemical/Composition Layers of the Earth
• Crust. The outermost rock layer, divided into continental and
oceanic crusts. The continental crust is 10-70 km thick and is
mostly granite and andesite. The oceanic crust is 5-10 km thick
and mostly basalt.
• Mantle. The mantle stretches from the below the crust to 2900
km below the surface. The upper part is partially molten and
the lower part is very dense. The main mantle rock is
peridotite.
• Core. The core is about 7000 km in diameter with a
temperature of 6000oC and a pressure of over 3 million
atmospheres. The inner core is a lumpy solid iron and nickel
sphere, and the outer core is a thick liquid iron and nickel layer.
Mechanical/Physical Layers of the Earth
• Lithosphere. Equivalent to the crust and uppermost layer of
the mantle (10 – 200 km thick), the lithosphere comprises of a
number of tectonic plates that 'float' on the asthenosphere. It is
rigid or solid.
• Asthenosphere. Ductile rocks that lie from below the
lithosphere. It is 660 km deep. It has fluid property (viscoelastic
solid – under certain conditions it is elastic and other conditions
it can deform as a plastic material). The ability of the
asthenosphere to flow slowly is termed as plasticity.
• Mesosphere. Solid rocks below the asthenosphere. It is solid
or rigid because of enormous pressure.
granite
andesite
basalt
iron
nickel