Earth's upper mantle is divided into two major rheological layers: the rigid lithospheric mantle (the uppermost mantle), and the more ductile asthenosphere, separated by the lithosphere-asthenosphere boundary.

Thickest Layer: The mantle is the thickest layer of the Earth, accounting for about 84% of the Earth’s volume. It extends approximately 2,900 kilometers beneath the crust, which makes it nearly twice the thickness of the Earth’s outer and inner cores combined.

Its chemical structure is of a silicate crust, a ferromagnesian mantle, and an iron-nickel core whose flowing upper portion generates the Earth's magnetic field.

Earth consists of three main layers: the crust, the mantle, and the core (Figure 3.1.1). The core accounts for almost half of Earth’s radius, but it amounts to only 16.1% of Earth’s volume.

Earth's outer core is a fluid layer about 2,260 km (1,400 mi) thick, composed of mostly iron and nickel that lies above Earth's solid inner core and below its mantle. [1][2][3] The outer core begins approximately 2,889 km (1,795 mi) beneath Earth's surface at the core-mantle boundary and ends 5,150 km (3,200 mi) beneath Earth's surface at the ...

The four primary layers are the crust, the mantle, the outer core, and the inner core. However, geologists subdivide these layers into a complex structure that better describes the Earth’s intricate composition and behavior.

Its chemical structure is of a silicate crust, a ferromagnesian mantle, and an iron-nickel core whose flowing upper portion generates the Earth's magnetic field.

The Earth is not a solid sphere — it’s made up of distinct layers, each with its own composition, density, and behavior. From the fragile crust we live on to the fiery outer core that generates Earth’s magnetic field, these layers reveal how our planet formed and how it continues to evolve today.

Schematic view of Earth's interior structure. Earth's inner core is the innermost geologic layer of the planet Earth.

The inner core is a solid ball of metal at the very center of the Earth, roughly 1,220 kilometers (about 760 miles) in radius. It sits beneath every other layer of the planet, surrounded by the liquid outer core, and begins at a depth of about 5,150 kilometers below the surface.

Geological cross section of Earth, showing the different layers of the interior. The internal structure of Earth is the spatial variation of chemical and physical properties in the solid Earth.

The four main layers of the Earth are the crust, mantle, outer core, and inner core. The Earth, like an onion, consists of several concentric layers, each with its own unique set of properties and characteristics.