Home > Encyclopedia of Science > Earth's Interior

• The crust
• Words to Know
• The mantle
• The core

The distance from Earth's surface to its center is about 3,975 miles (6,395 kilometers). Scientists have divided the interior of Earth into various layers, based on their composition. The crust, or outer portion, varies in depth from 5 to 25 miles (8 to 40 kilometers). Below the crust is the mantle, which extends to a depth of about 1,800 miles (2,900 kilometers). Below that is the core, composed of a liquid outer core about 1,380 miles (2,200 kilometers) in depth, and a solid inner core about 780 miles (1,300 kilometers) deep.

From direct observation, core samples, and drilling projects, scientists have been able to study the rock layers near the planet's surface. However, this knowledge is limited. The deepest drill hole, just over 9 miles (15 kilometers) in...