Inside the Earth

The Layers of the Earth © Copyright 2006.  M. J. Krech. All rights reserved.

The Three Main Layers The three main layers of the Earth are the crust, the mantle, and the core. These layers vary greatly in size, composition, temperature, and pressure.

The Crust The crust is the layer that forms the outer “skin” of the earth It is a layer of solid rock that includes both dry land and the ocean floor. It is the thinnest layer of the earth and is between 5-100 km thick. It is thickest under mountains and thinnest beneath the ocean. 2 types of crust Oceanic (very dense, made of basalt) Continental (less dense, made of granite)

Oceanic and Continental Crust

The Crust The crust of the Earth is broken into many pieces called plates. The plates "float" on the soft, semi-rigid asthenosphere.

The Mantle The mantle is the layer of the earth between the crust and core. The mantle is made up of rock that is very hot, but solid. Scientists further divide the mantle into layer based on physical characteristics of those layers: lithosphere, asthenosphere, and lower mantle.

The Mantle’s Lithosphere The crust and the upper layer of the mantle together make up a zone of rigid, brittle rock called the Lithosphere. In Greek, litho means “stone”.

The Mantle’s Asthenosphere The middle layer of the mantle is hotter and under increasing pressure. The asthenosphere is a softer layer than the rigid lithosphere, but is still considered to be solid. It is soft enough to bend like plastic, but hard enough to stub your toe if you kicked it.

Convection Currents in the Mantle The middle mantle "flows" because of convection currents. Convection currents are caused by the very hot material at the deepest part of the mantle rising, then cooling and sinking again --repeating this cycle over and over.

The Core At Earth’s center you will find the core which is broken into two parts- the outer core and the inner core. The core (both the outer and inner) makes up Earth’s thickest layer

The Outer Core The Outer Core is a layer of molten metal (iron and nickel) that surrounds the inner core. The outer core is liquid and scientist believe that the movements in the liquid outer core create Earth’s magnetic field.

The Inner Core The Inner core is a dense ball of solid metal. The core of the earth makes up about 33% of Earth’s mass Temperatures in the inner core ranges up to 5,000 degrees Celsius.