Structure of the Earth Overview

Structure of the Earth

• The Earth is divided into three main layers: the crust, mantle, and core, distinguished by their relative position, composition, and density.

Crust

• The outermost solid layer, varying in thickness from 5-70 km, with an average thickness of 35 km.
• Composed of a variety of rocks, including granite, basalt, and sedimentary rocks.
• Density: approximately 2.7-3.0 g/cm³.

Mantle

• Lies beneath the crust, extending from about 35 km to 2,900 km in depth.
• Divided into the upper mantle and lower mantle, separated by a transition zone.
• Composed primarily of hot, viscous rock (olivine, pyroxene, and garnet).
• Density: increases with depth, ranging from 3.3 to 5.6 g/cm³.

Outer Core

• A liquid layer, 2,250 km thick, composed of a nickel-iron alloy.
• Temperature: approximately 4,000-6,000°C (7,200-11,000°F).
• Density: around 9.9-12.2 g/cm³.

Inner Core

• A solid, innermost layer, with a radius of approximately 1,220 km.
• Composed primarily of iron (~85%) and nickel (~10%), with small amounts of lighter elements.
• Temperature: approximately 5,000-6,000°C (9,000-11,000°F).
• Density: around 12.8-13.1 g/cm³.