The Earth's internal structure is a concentric layered structure, differentiated from the core to the surface into the core, mantle, and crust, with the boundaries between the Earth's core, mantle, and crust mainly inferred based on the abrupt changes in seismic wave propagation velocity.

The Earth's crust refers to a solid outer shell made of rock, the outermost layer of the Earth's solid sphere, and an important component of the lithosphere. Based on seismic wave studies, the interface between the crust and mantle is determined to be the Mohorowicz discontinuity (Mohorowicchi plane).

Beneath the crust, above the core, is the Earth's middle layer, about 2,865 km thick, mainly composed of dense rock-forming material, which is the largest and most massive layer inside the Earth. The mantle can be further divided into upper and lower mantles.

The Earth's core is the core part of the Earth, located at its innermost part. It has a radius of about 3470 km, is mainly composed of iron and nickel, has a high density, and the average density of core material is about 10.7 grams per cubic centimeter. The temperature is extremely high, reaching 7000°C. The Earth's core can be further divided into the inner core and the outer core.

The inland core is located at the Earth's innermost part, about 1216 km thick, with an average density of 12.9 grams per cubic centimeter. Its main components are heavy metals mainly iron and nickel, hence it is also called the iron-nickel core.

The outer core is above the solid inner core, beneath the mantle, composed of liquid iron and nickel, with a thickness of about 2254 km.