Download Plate Tectonics

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 outermost layer of the
Earth.
 It is between 5 and
100 kilometers
thick.
 It is the thinnest of the Earth’s layers.
 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.
It is much thicker
than the crust.
It contains about
67% of the Earth’s
mass.

It is a layer of hot rock.

The mantle is denser than the crust.

It consists of a number of zones.
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
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.
The Mantle

As you go deeper into
the mantle, heat and
pressure increase.
 This makes the rock
less rigid.
 It has the consistency
of tar and can bend much like plastic (semi molten).
 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.

This lower solid part of the mantle is called the
mesosphere.
The Core

The layer of the Earth that extends
below the mantle to the center of
the Earth is the core.
 The core makes up about 1/3 of
the Earth’s mass.

It has two layers:



A liquid outer core
A solid inner core
Both are made of iron and nickel.

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.
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 plastic-like layer of the
mantle is called the
asthenosphere.

The innermost rigid part of
the mantle is called the
mesosphere.

The core has two parts.

The outer core is liquid.

The inner core is solid.