Earth's Interior

What are the features of Earth’s Crust, Mantle, and Core?

The three main layers of earth are the crust, the mantle, and the core. These layers vary greatly in size, composition,temperature, and pressure.

The Core

The Core - Is made mostly of the metals iron and nickel. It consists of two parts, a liquid outer core and a solid inner core.


The outer core - a layer of molten metal surrounding the inner core.


The inner core - a dense ball of solid metal.


The outer core is 2,258 kilometers thick. The inner core is a solid ball. Its radius is 1,222 kilometers. The total radius of the core is 3,480 kilometers. Earth's core occupies the center of the planet.

The Crust

The Crust - A layer of solid rock that includes both dry land and the ocean floor.


The main elements in the crust are oxygen and silicon. The crust is much thinner than the layer that lies beneath it. In most places, the crust is between 5 and 40 kilometers thick. It is thickest under high mountains, where it can be as thick as 80 kilometers, and thinnest between the ocean. The crust that lies beneath the ocean is the oceanic crust. The composition of the oceanic crust is nearly constant. Its overall composition is much like basalt, with small amounts of ocean sediment on top. Basalt is a dark, fine-grained rock. Continental crust, the crust that forms the continents, contains many types of rock. So unlike oceanic crust, its composition varies great. But overall the composition of the crust is much like granite. Granite is a rock that usually is a light color and has coarse grains. Both granite and basalt have more oxygen and silicon than they have any other element.

The Mantle

The Mantle - Is made of rock that is very hot, but solid. Scientists divide the mantle into layers based on the physical characteristics of those layers. Overall the mantle is nearly 3,000 kilometers thick.


The Lithosphere - The uppermost part of the mantle is brittle rock, like the rock ofthe crust. Both the crust and the uppermost part of the mantle are strong, hard, and, rigid. So geologists often group the crust and uppermost mantle into a single layer called the lithosphere. Earth's lithosphere averages about 100 kilometers thick.


The Asthenosphere - Below the lithosphere, the material is hotter and under increasing pressure. As a result, the part of the mantle just beneath the lithosphere is less rigid than the rock above. Over thousands of years this part of the mantle can bend like a metal spoon. But it's still solid. If you kicked it, you would stub your toe. This soft layer is called the asthenosphere.


The Mesosphere - Beneath the asthenosphere, the mantle is hot but more rigid. The stiffness of the mesosphere is the result of increasingly high pressure. This layer includes a region called the transition zone, which lies just beneath the asthenosphere. It is also includes the lower mantle, which extends down to Earth's core.

What are some important vocabulary terms I should know?

Seismic Wave - When earthquakes occur, they produce Seismic Waves.


Pressure - Pressure results from a force pressing on an area.


Basalt - A dark, fine-grained rock.


Granite - A rock that usually is a light color and has coarse grains.

How do geologists learn about Earth's Interior?

Geologists have used two main types of evidence to learn about Earth's Interior: direct evidence from rock samples and indirect evidence from seismic waves.