Here’s a clear, concise overview of Earth's interior layers and their main characteristics. Core ideas in brief
- Earth is stratified into three broad chemical layers: crust, mantle, and core.
- Each of these broad layers contains important subdivisions that define physical behavior and composition.
Detailed layers (from exterior to center)
- Crust
- Continental crust: thicker and less dense, mostly granitic rocks.
- Oceanic crust: thinner and more dense, primarily basaltic rocks.
- The crust sits atop the mantle and is delineated by the Mohorovičić discontinuity (the Moho), the boundary where seismic waves speed up as they pass into the mantle.
- Mantle
- Upper mantle: includes the asthenosphere, a zone of partially molten rock that allows the tectonic plates to move on top of it.
- Lower mantle: more rigid and extends down to the outer core boundary.
- The mantle makes up the vast bulk of Earth’s volume and is rich in silicate minerals with magnesium and iron.
- Core
- Outer core: a liquid shell primarily of iron and nickel, extending roughly from about 2,900 km (1,800 miles) below the surface to about 5,150 km (3,200 miles) below the surface; its convection generates Earth’s magnetic field.
* Inner core: a solid sphere predominantly iron-nickel alloy, with a radius close to 1,220 km (760 miles); extreme pressures keep it solid despite the high temperatures.
Key distinctions and context
- The crust, mantle, and core are defined both chemically (by composition) and physically (by behavior under pressure and temperature).
- Seismology is the primary tool for studying these boundaries, revealing major discontinuities like the Moho (crust-mantle) and the core-mantle boundary.
- Common simplifications describe four principal physically distinct layers (inner core, outer core, mantle, crust), but most modern summaries emphasize three broad chemical layers with notable internal subdivisions. Various educational sources present these perspectives with slight emphasis differences.
If you’d like, I can tailor this into a quick study guide, a visual diagram description, or a short quiz to test your knowledge of each layer and its properties.
