Layers of the Earth

Classification of Earth’s Layers There are two ways in which Earth’s layers are classified: 1) By composition (The type of rock each layer is made of) 2) By mechanical properties ( The way in which each layer moves)

Earth’s Layers by Composition Before we can discuss the Earth’s Layers by Composition, we must know the difference between Felsic and Mafic rocks, which are classified according to their silica (Silicon Dioxide (SiO2)) content. Felsic and Mafic Classifications Felsic Rock is more than 65 percent silica. Intermediate Rock is between 55 and 65 percent silica. Mafic Rock is between 45 and 55 percent silica. Ultramafic Rock is less than 45 percent silica.

Lighter in color and weight Darker in color and heavier in weight

The Earth’s Crust The crust is less than 1% of Earth’s mass. The two types are oceanic crust and continental crust. Continental crust is felsic and oceanic crust is mafic.

The Earth’s Mantle The mantle consists of hot, dense, semisolid, ultramafic rock. It makes up about 68% of Earth's mass.

The Earth’s Core The core is the very hot center of the Earth and makes up about 31% of the planet. The inner core is mostly solid iron metal, while the outer core is mostly melted iron and nickel. The inner core is very hot but cannot melt due to the pressure of all the Earth around it.

Earth’s Layers by Mechanical Properties The lithosphere is composed of both the crust and a portion of the upper mantle and behaves as a brittle, rigid solid. The asthenosphere is partially molten upper mantle material and behaves plastically and can flow. The lithosphere “floats” on top of the asthenosphere, with heavier parts of the lithosphere riding lower than its lighter parts.

Layers of the Earth Interactive Model and Video http://www.learner.org/interactives/dynamicearth/structure.html https://www.youtube.com/watch?v=NAHY6965o08