earth's internal structure

• the outermost layer of earth is the crust, the part which we step on.
• the crust is made up of hard, solid rock with soil on the topmost part.
• the oceanic crust consists of basaltic rock and has a density of about 3.0 g/cm3.
• rocks in the oceanic crust are less than 200 million years old.
• the continental crust is made up of granite-type rocks and has a density of about 2.7 g/cm3.
• the continental crust is about 300 million years old.
• the next layer of the earth is the mantle which is about 2885 kilometers thick.
• the mantle is subdivided into the upper mantle and the lower mantle.
• seismic studies indicate that the outer mantle is the most solid.
• the lower mantle is also solid but behaves somewhat "plastic".
• the inner part of earth is the core.
• the core consists mostly of iron and nickel.
• the core is subdivided into the liquid outer core and solid inner core.
• the lithosphere is the rigid outer layer of earth.
• the lithosphere includes the crust and the uppermost mantle.