Structure of the Earth  Earth’s Interior is divided into 3 layers that have very different properties:  Crust  Mantle  Core  Our knowledge of these layers has come mainly from the study of earthquake waves.

The Crust  The crust is the outer- most layer of the Earth.  It is the thinnest of the Earth’s layers.  It is between 5 and 100 kilometers thick.  It is where we live.

The Crust  The crust is made up mostly of oxygen, silicon & aluminum.  There are two types of crust  Oceanic crust  Continental crust

Types of Crust  Oceanic crust is the crust that lies below the Earth’s oceans.  It consists mostly of basalt – a dark, dense igneous rock with a fine-grained texture.  Continental crust forms the continents and consists mostly of granite - a less dense igneous rock with larger crystals that is usually light in color.

The Mantle  The next layer after the crust is the mantle.  It lies from about 40 to 2,900 kilometers below the surface.  The mantle is denser than the crust.  It contains about 67% of the Earth’s mass.  It is much thicker than the crust.  It is a layer of hot rock.  It consists of a number of zones.

 The crust and the uppermost part of the mantle are very similar. They are both rigid.  Together they are called the lithosphere.  Litho means “stone.”  The lithosphere is about 100 kilometers thick. LITHOSPHERELITHOSPHERE Click for graphic

The Mantle  As you go deeper into the mantle, heat and pressure increase.  This makes the rock less rigid.  This plastic-like layer of the mantle is called the asthenosphere.  The lithosphere floats on top of the asthenosphere.  Beneath the asthenosphere solid mantle material extends all the way to Earth’s core.  It has the consistency of tar and can bend much like plastic (semi molten).  This lower solid part of the mantle is called the mesosphere.

The Core  The core makes up about 1/3 of the Earth’s mass.  Both are made of iron and nickel.  The layer of the Earth that extends below the mantle to the center of the Earth is the core.  Despite enormous pressure, the molten metal of the outer core behaves like a thick liquid.  The inner core is a dense ball of solid metal.  The pressure is so great that the iron atoms cannot spread out and become a liquid.  It has two layers:  A liquid outer core  A solid inner core

Earth’s Magnetic Field  Currents in the liquid outer core cause the solid inner core to spin.  The inner core spins at a slightly faster rate than the rest of the planet.  This movement creates the Earth’s magnetic field, which causes the entire Earth to act like a giant bar magnet.

Review  The Earth is made of three basic layers.  The crust and the top, rigid part of the mantle make up the lithosphere.  The core has two parts.  The innermost rigid part of the mantle is called the mesosphere.  The plastic-like layer of the mantle is called the asthenosphere.  The inner core is solid.  The outer core is liquid.