4.2: The Layered Earth

The Layered Earth

Before we can address plate tectonics, we must consider Earth’s layered interior. At first glance, we can identify three major regions which are distinct based on their overall composition: the core, mantle, and crust. However, more layers are visible if we also consider mechanical properties of the layers. By examining these properties, five major layers are identified, the lithosphere (upper mantle and crust), asthenosphere, lower mantle, outer core, and inner core. For a visual journey through the interior of the Earth, visit the BBC's Journey to the Center of the Earth Links to an external site. or take a trip to the Earth’s core by watching the video below.

A cross-section of Earth, illustrating the different layers. Moving from the exterior towards Earth’s center: The lithosphere includes the crust and upper mantle, the asthenosphere, lower mantle, outer core, and inner core. — **Figure 4.1**: The Earth’s layered structure (CC-BY 4.0; Chloe Branciforte, own work).

**Table 4.1:** The layers of the Earth have distinct and unique properties
(CC-BY 4.0, Chloe Branciforte, own work).
Properties	Lithosphere	Asthenosphere	Lower Mantle	Outer Core	Inner Core
Physical behavior	Solid, rigid, brittle	Solid, plastic (ductile)	Solid, rigid, brittle	Liquid	Solid, rigid, not brittle
Overall Thickness (mi & km)	62 mi (100 km)	115 mi (185 km)	1800 mi (2897 km)	1367 mi (2200 km)	776 mi (1249 km)