COE - Layers of the Earth Lesson

 

Layers of the Earth

While the Earth was molten, many of the materials that make up its mass rearranged themselves according to density - the denser elements and compounds sank towards the center of the Earth and the less dense materials floated to the surface, where they cooled and hardened.

There are three distinct chemical layers of the Earth - the core, the mantle and the crust. The core is thought to be mainly composed of iron and is spherical in shape. The mantle is composed of heavier silicates containing calcium, magnesium, and iron. The crust is made primarily of lighter silicates, containing aluminum and smaller amounts of iron, calcium, magnesium, and other elements.

The Earth's layers can also be described in terms of physical properties. The core can actually be divided into two parts - a solid inner core and a liquid outer core. Both are thought to be made of the same materials - mostly iron and nickel - but the inner core is under more pressure than the outer core, which keeps the inner core from melting into a liquid. The mantle can also be divided into two parts; a solid mesosphere below and a semi-solid layer called the asthenosphere on top. The asthenosphere is often described as being "plastic", meaning that it mostly behaves like a solid, but bends and flows very slowly, much in the way that glaciers do on the Earth's surface. On top of the asthenosphere is the solid lithosphere, which is essentially the same as the crust:

Chemical	Physical
Crust	Solid Lithosphere
Mantle	"Plastic" Asthenosphere
	Solid Mesosphere
Core	Liquid Outer Core
	Solid Inner Core

Watch the video below to learn more:

Complete the Earth Layers activity below:

 

There is even differentiation within the crust itself; a relatively thin layer (>10 km thick) of crust creates the ocean floors, whereas thicker sections (25-75 km thick) form the continents. The oceanic crust, however, is denser than the continental crust, which means that when the two types collide with each other, the oceanic crust sinks below the continental crust:

 

IMAGES CREATED BY GAVS OR OPENSOURCE