Earth’s Interior6th Grade Earth ScienceMs. Mudd

ObjectivesExplain how geologists learn

about Earth’s inner structures.Identify the characteristics of

Earth’s crust, mantle, and core.

Key TermsSeismic wavesCrustMantleAsthenosphereInner and outer coreLithosphereBasaltgranite

Exploring Inside the EarthEarth’s surface is constantly

changing.Throughout the planet’s history it

has been pushed down, bent, pushed up and broken.

All of this movement makes the Earth look very different from the way it did millions of years ago.

Exploring inside the Earth.Geologists are unable to dig a

hole to the center of the Earth.The extreme conditions of the

Earth’s interior prevent exploration far below the surface.

How deep is deep?The deepest mine in the world, a

gold mine in South Africa, reaches a depth of 3.8 km.

You would have to travel 1600 times that to reach the Earth’s center.

6,000 km

Exploring the EarthGeologist use two main types of

evidence to learn about the Earth’s interior.

Direct evidence from rock samples.Indirect evidence from seismic

waves.

Rock SamplesRocks from inside Earth give

geologists clues about Earth’s structure.

Rock SamplesGeologists have drilled holes as deep

as 12 km into Earth.The drills bring up samples of rocks

to study.Geologists can make inferences.In addition, forces inside the Earth

blast rock to the surface from depths of more than 100 km.

These rocks provide information about the interior.

Finding Indirect EvidenceSeismic WavesPrimary Waves (P waves)

◦Back and Forth motion◦First to arrive after earthquake◦Can travel through liquid and solids

Secondary Waves (S waves)◦Up and Down motion◦Cannot travel through liquid

Seismic Waves Paths Through the Earth

http://phschool.com/atschool/earth_science/powerpoints/PHESCh01.ppt#16

S Waves

P Waves

Finding Indirect EvidenceThe denser the rock the more

quickly the wave will travelAs P waves travel from one type

of material to another the waves bend or refract

S waves stop at the outer core indicating that it must be liquid

Finding Indirect EvidenceThe Moho

◦The name of the boundary between the mantle and the crust. Named for Andrija Mohorovicic

◦An area where seismic waves suddenly speed up (due to rock density)

Earth’s Interior Showing P and S Wave Paths

Earth’s Layered StructureEarth’s interior consists of three

major zones defined by their chemical composition—

the crust, mantle, and core.

Check Your NotesWhat are the two types of

evidence geologists used to learn about the interior of the Earth?

Give an example of each.

AnswerIndirect and Direct evidence.Seismic waves and rock samples.

Check your notesWhat are the two types of

waves?

AnswerP waves and S waves.P waves move back and forth.S waves move up and down.

Check your NotesWhat are the three main layers of

the Earth?

AnswerCrustMantleCore

http://teach.fcps.net/trt20/projects/EKU/Default.htm

Inside Earth’s InteriorPhysical Classification: 5 layers

based on physical traits

Lithosphere:◦Crust and uppermost part of mantle

◦Rigid layer of rock◦“Litho” means stone◦Approximately 100 km thick

Earth’s Layered Structure

http://phschool.com/atschool/earth_science/powerpoints/PHESCh01.ppt#16

LithosphereThe Earth’s crust and upper mantle are broken into sections called plates

Plates move around on top of the mantle like rafts

Earth’s InteriorChemical ClassificationCrust -

◦Continental Crust: Mostly granite Average thickness 30km

◦Oceanic Crust: Mostly basalt Average thickness 5 – 8 km Denser than continental crust

Thin, rocky outer layer

2 Types of PlatesOcean plates - plates below the oceans made up of mostly basalt

Continental plates - plates below the continents made up of mostly granite

Inside Earth’s InteriorAsthenosphere:

◦Upper mantle – higher temperature and pressure

◦Soft rock that the lithosphere floats on◦“Asthenes” means weak◦Convection currents in the

asthenosphere cause plates to moveMesoshpere

◦Rest of mantle which is solid material due to high pressure

Earth’s Outer CoreAt the center of Earth is the core. The core is made mostly of iron and

nickel and possibly smaller amounts of lighter elements, including sulfur and oxygen.

The core is about 4,400 miles (7,100 kilometers) in diameter, slightly larger than half the diameter of Earth and about the size of Mars.

The outermost 1,400 miles (2,250 kilometers) of the core are liquid.

Currents flowing in the core are thought to generate Earth's magnetic field.

Earth’s Inner CoreGeologists believe the innermost part of the

core, about 1,600 miles (2,600 kilometers) in diameter, is made of a similar material as the outer core, but it is solid.

The inner core is about four-fifths as big as Earth's moon.

Earth gets hotter toward the center. Geologists believe the temperature of Earth's outer core is about 6700 to 7800 degrees F (3700 to 4300 degrees C). The inner core may be as hot as 12,600 degrees F (7000 degrees C)--hotter than the surface of the sun. But, because it is under great pressures, the rock in the center of Earth remains solid.

Exit TestWhat are the two types of plates?

AnswerContinental and Ocean

Question 2What is the ocean plate mainly

made of?(hint; type of rock)

AnswerBasalt

Question 3What layer are plates found?

AnswerLithosphere

Question 4What does “Athenes” mean?

Answerweak

http://www.youtube.com/watch?v=6-x9eok__Cw&feature=related

Part 1

http://www.youtube.com/watch?v=Rei8G7RNiDI&feature=related

Part 2

http://www.youtube.com/watch?v=gHgRDnvOnM4&feature=related

Part 3

http://www.youtube.com/watch?v=SdmuX0nv-xE

Part 4

http://www.youtube.com/watch?v=bbtFsbuopAA&feature=more_related