Journey to the Journey to the Center of the Earth!Center of the Earth!

• When the Earth first formed gravity pulled most of the heavy materials to the center of the Earth

• Lighter materials “floated” to the surface of the Earth

• As a result of gravity, the Earth separated into four main layers

The Layers of the EarthThe Layers of the Earth

• The thinnest layer of the Earth

–On average it is:• 3 miles thick under the oceans• 19 miles thick under the continents

The CrustThe Crust

•• There are two main types of crust:There are two main types of crust:– Continental Crust

• Thicker than oceanic crust– Up to 35 miles thick

• Least dense layer in the Earth

– Oceanic Crust• Much thinner than continental crust• Slightly more dense than continental crust

The CrustThe Crust

Nobody has ever drilled through the crust

The CrustThe Crust

CrustCrust

The MantleThe Mantle• Made up of heavier materials than the

crust.

• Slightly liquid– Similar to silly putty or play-dough

• The largest layer in the Earth

• Asthenosphere

– A layer of the mantle just beneath the crust.

• The asthenosphere is more fluid than the rest of the mantle.

The MantleThe Mantle

• Mohorovi čić Discontinuity

– Also known as: the border between the mantle and the crust.

– Called the “Moho” for short

– Named after Andrija Mohorovičićwho located the border.

The MantleThe Mantle

http://www.earthscrust.org/earthscrust/science/historic/img/mohorovicic.gif

MantleMantle MohoMoho

THICK LIQUIDTHICK LIQUID

Outer CoreOuter Core• Located 1,800 miles beneath the surface

• Mainly made out of liquid iron and nickel

– The liquid iron moving around in the outer core creates the Earth’s magnetic field.

Outer Outer CoreCore

LIQUIDLIQUID

(Iron & Nickel)(Iron & Nickel)

• Located 3,200 miles beneath the surface

• Made from solid iron and nickel

• Very, very hot, but stays solid because the entire Earth is pushing down on the inner core.

Inner CoreInner Core

Inner CoreInner CoreSOLIDSOLID

(Iron & Nickel)(Iron & Nickel)

Inner Inner CoreCore

Outer Outer CoreCore

MantleMantle MohoMohoCrustCrust

How Do We Know?How Do We Know?• No one has even drilled through the crust,

so how do we know what the layers are?

– Earthquakes cause waves to go through the center of the Earth

– Scientists use earthquake waves like a submarine uses SoNAR.

• The waves bounce off the layers and tell scientists where a boundary is located

Heat in the EarthHeat in the Earth• The temperature in the center of the Earth

gets up to about 10,000°F

• Where does that heat come from?

Where Does the EarthWhere Does the Earth ’’s s Heat Come From?Heat Come From?

1. Heat from when the Earth formed� Comets & Meteors striking the Earth

2. Radioactive Elements in the Earth� They decay and release huge amounts of heat.

3. Gravity pulling elements towards the center of the Earth

� Friction between materials rubbing against each other.