8.4 Earth’s Layers

Layers by Composition Earth’s interior consists of three major zones defined by its chemical composition. CrustMantleCore

Crust Thin, rocky outer layer of Earth, is divided into oceanic & continental crust. Oceanic crust is made up of igneous rocks basalt and gabbro. Continental crust is made up of many rock types.

Mantle Over 82 % of Earth’s volume is contained in the mantle Mantle – a solid, rocky shell that extends to a depth of 2890 km. The boundary between the crust & mantle shows a change in chemical composition.

Core Sphere composed of an iron-nickel alloy. Extreme pressure is found here.

Layers by Physical Properties Earth’s interior gradually increases in temperature, pressure, and density with depth. Earth is divided into layers based on their physical properties LithosphereAsthenosphere Outer Core Inner Core

Lithosphere & Asthenosphere Lithosphere – Earth’s outermost layer that consists of the crust and uppermost mantle. It forms a relatively cool, rigid shell Asthenosphere – located below the lithosphere. Relatively soft, and weaker layer. Warmer than the lithosphere

Lower Mantle Located near the base of the mantle More rigid layer Rocks are still very hot and capable of gradual flow

Inner & Outer Core Composed mainly of iron-nickel alloy Divided into 2 main regions that both have different physical properties Outer Core- liquid layer; flow of metallic iron in this zone is what creates the Earth’s magnetic field Inner Core- High temperatures; material is compressed into a solid state by the high pressure