Edward Suess suggested that earth was differentiated into three parts SIAL, SIMA, NIFE. The uppermost SIAL which has granite and is composed of silicon and aluminum floats over SIMA which is more denser and consists of silicon and magnesium. This theory has been replaced with the more complex structuring theory. From seismic studies, it has been shown that earth has 3 parts crust, mantle and core
The Crust ![[Pasted image 20220310102314.png]]
it is the outermost and brittle part of the earth, oceanic crust is thinner compared to continental
The Mantle ![[Pasted image 20220310102811.png]] The mantle is composed of SIMA, moho discontinuity or the mohorovicic discontinuity separates the mantle from crust. Outer portion of mantle is called Asthenosphere it is the main source of magma, the mantle is in solid state and is made up of silicate minerals rich in iron and magnesium.
Core The core is the innermost layer of Earth, outer layer is in liquid state while the inner core is solid, the core-mantle boundary is called Gutenberg Discontinuity
Asthenosphere and the Lithosphere ![[Pasted image 20220310104132.png]] The lithosphere being brittle and asthenoshpere being soft and plastic means the former can easily move over the latter, each lithospheric plate can easily be as large as a continent. Hence lithospheric plates may separate at one place while forming ridges and mountains in another ([[Continental Drift]] ?).