Читать книгу Earth Materials - John O'Brien - Страница 18

The layers within Earth defined principally on the basis of mechanical properties (Figure 1.1; right side) include: (1) a relatively strong lithosphere of variable thickness to an average depth of ~100 km that includes all of the crust and the upper part of the mantle, (2) a weaker asthenosphere that extends to depths between ~100 and 660 km and includes a transition zone from ~400 to 660 km, and (3) a mesosphere or lower mantle from ~660 to 2900 km. The underlying core is divided into a liquid outer core (~2900–5150 km) and a solid inner core below ~5150 km to the center of Earth. Each of these layers is distinguished from the layers above and below by its unique mechanical properties. The major features of each of these layers are summarized in the next section.