The Layers of the Earth

Earth Layers

• The Earth is divided into 4 main layers.

Inner CoreOuter CoreMantle Crust

The Crust Outermost layer of the Earth The Earth’s crust is like the skin of an apple. It is

very thin compared to the other three layers. The crust makes up 1% of the Earth and is called

the “rock and mineral” layer. The crust of the Earth is broken into many pieces

called plates. At the junction of these plates some interesting

things occur!

Plate Tectonics

Sea-Floor Spreading

Volcanoes

Earthquakes

And what type of crust would you like with your Earth?

• There are two types of crust.– Continental crust– Oceanic crust

Continental Crust

• Makes up the continents

• Contains light colored rocks such as granite.

• Floats high on the mantle

Oceanic Crust

• Makes up the ocean floor

• Contains the dense rocks such as basalt

• Thinner than the continental crust

The Mantle The mantle is the layer between the

crust and the outer core. The mantle is the largest layer of the

Earth. The mantle is made up of MAGMA (hot

molten rock). Because of the heating and cooling of

liquid rock, convection currents occur. These currents force the plates of the crust to move.

Mantle Zones: Lithosphere

• Thin, uppermost part of the mantle and crust; rigid, brittle rock

• Floats on the athenosphere, and slides around very slowly.

• The upper part of the lithosphere melts rocks, forming a substance called magma.

Magma

• Magma (melted rock) moves like hot oatmeal.

• Uneven heating causes material in the mantle to constantly and slowly rise & fall in convection currents.

• Convection Currents: process by which hot fluid rises to the surface, and then sinks again, like soup being heated in a saucepan

OUTER CORE

CRUST

MANTLE

HOT LIQUID RISES

COOL LIQUID SINKS

CONVECTION IN THE MANTLE

Mantle Zones: Asthenosphere

• Hot, weak zone directly under the lithosphere

• Flows at a very slow rate like hot asphalt under a heavy weight

• The movement (convection currents) of the asthenosphere is the reason that the crustal plates of the Earth move

Core

• Deep within the Earth is the core

• The core is made mostly of nickel & iron

• Twice as dense as the mantle.

• Main source of heat that triggers the convection currents

• The core is made of two layers

Outer Core The outer core of the Earth is a ball of

very hot liquid metal. The outer core is made up of mostly

iron and is very dense. Because this liquid metal is moving,

positive and negative particles are created and released that create the Earth’s MAGNETIC FIELD.

Magnetic Field

Inner Core The inner core of the Earth has

temperatures and pressures so great that the metals are squeezed together and are not able to move.

Therefore; the inner core is a solid. The temperature in the core is nearly as

hot as the surface of the SUN!

Plate Tectonics

• Pieces of the lithosphere that move around

• Each plate has a name• Fit together like jigsaw puzzles• Float on top of mantle similar to ice

cubes in a bowl of water

Continental Drift

http://members.enchantedlearning.com/subjects/astronomy/planets/earth/Continents.shtml

Alfred Wegener 1900’sContinents were once a single land mass that drifted apart.

Fossils of the same plants and animals are found on different continents

Called this supercontinent Pangea, Greek for “all Earth”

245 Million years ago

Split again – Laurasia & Gondwana 180 million years ago

Evidence of Pangea

Sea Floor Spreading

Sea Floor Spreading

• Mid Ocean Ridges – underwater mountain chains that run through the Earth’s Basins

• Magma rises to thesurface and solidifiesand new crust forms

• Older Crust is pushedfarther away from theridge

How Plates Move

http://pubs.usgs.gov/gip/dynamic/unanswered.html

Different Types of Boundaries

http://pubs.usgs.gov/gip/dynamic/understanding.html

Divergent Boundary – Arabian and African Plates

Divergent Boundary – Iceland

http://pubs.usgs.gov/gip/dynamic/understanding.html

Divergent Boundary - Oceanic

http://www.geology.com

Divergent Boundary - Continental

http://www.geology.com

Convergent Boundary – Indian and Eurasian Plates

Convergent Boundary – Oceanic & Continental

http://pubs.usgs.gov/gip/dynamic/understanding.html & http://www.geology.com

Convergent Boundary – Oceanic & Oceanic

http://pubs.usgs.gov/gip/dynamic/understanding.html & http://www.geology.com

Convergent Boundaries - Continental

http://pubs.usgs.gov/gip/dynamic/understanding.html & http://www.geology.com

Transform Boundary – San Andreas Fault

www.geology.com