Inside Edition

The Earth’s Interior:

A Hot Topic

A Planet at Rest?From the surface or from space the earth appears stable and calmExcept for infrequent violent volcanic and earthquake activity the earth hides its volatile natureThe key to understanding this side of the earth is understanding its interior

A Model of the Earth

Inner CoreOuter CoreMantleCrust

DifferentiationRemember how the Earth

Formed?

The Nebula Hypothesis

Planetesimals joined together to form protoplanets which were molten, at first

Dense materials like iron and nickel would tend to sink towards the middle

As cooling progressed lighter materials floated to the surface like “scum” and formed the crust

This was all completed about 4 billion years ago

Inner Core1216km (754 miles) in radiusRich in Iron and NickelIntense Pressure and Heat:

37000c (67000 f)

Dense materials sank to core as earth cooledSolid

Outer Core2270km (1410miles) thick Molten Iron and Nickel1500ºcLess pressure than inner coreliquidInner and outer core = 1/6 volume, but 1/3 mass

Mantle2900km (1800miles) thick Mainly Fe, Mg, Si, and OAbout 1200ºcMakes up 2/3 of Earth’s massLess pressure than cores, but still pretty intensePlasticlike-partially molten compostion that can slowly “flow”

Crust30-40km(19-25miles) average thicknessBeneath mountains can reach 43 milesThis thin layer that floats on denser mantleAverage composition is basalticSolid – Made of Plates•if you were to imagine the Earth as a soccer ball, the crust would be about ½millimeter thick.

The Thickness of the Crust Varies:

•This is a contour map of the thickness of the Earth's crust. The contour interval is 10 km; it also include sthe 45 km contour for greater detail on the continents.

•Where are the thickest parts of the crust?

Rock SolidContinental Crust

Thickest type of crust;- can be 43 miles thick beneath mtns.Very old rocks, 3.8 billion years oldLighter granitic composition

Do You Want Some Water With

That Crust?Oceanic Crust

Thinnest part of the crust, 4-7 miles thickRocks are relatively young, only 200 million years oldDense basaltic composition

Crust and Mantle

Lithosphere – cool, rigid upper layer of earthAsthenosphere – softer layer of the earth under the lithosphereMesosphere – very slowly flowing layer under the asthenosphere

The interaction of the crust and mantle gives rise to tectonic activity and crustal movement

The crust and mantle are broken down into three different zones

LithosphereComposed of the Crust and upper mantle

Solid – rigid plates made of the lithosphere

Varies from a few to 190 miles thick (62 miles average)

Continental CrustOcean Water

Upper MantleLithosphere

Oceanic Crust

AsthenosphereVery hot, weak zone of the upper

mantle capable of flowing

Temperatures reach 26000F – hot enough to melt some of the mantle material

This creates a soft layer about 200 miles thick that the overriding lithosphere “floats” upon

The lithosphere can move independently of the asthenosphere

So What?

Why is this important to

know?

The movement of the lithosphere created

because of the uneven heating of the interior of the earth causes many

things, like….

Earthquakes

And……

Volcanoes

Coloring the Earth’s Plates:

Color each plate a different color

•Be sure can still see the arrows showing the direction the plates are moving

•Answer the questions associated with the map