The Structure of the Earth and Plate Tectonics

The Structure of the Earth and Plate Tectonics

Lesson Objectives

This lesson will teach you everything you need to know about the Structure of the Earth and Plate Tectonics. By

the end of this lesson you will be able to…

1. Name and describe Earth’s main layers.2. Name and describe three types of plate boundaries

Instructions

• Complete this lesson on your own and at your own pace.• Use the navigational buttons along the bottom to move

throughout the lesson.• Take notes as you go.The objectives (on the previous

page) will be assessed by practice quizzes and on our Chapter Test.

• After linking to a website, simply close your browser window to return to this lesson.

• Have a pencil & paper handy.• Have fun!

Structure of the Earth

• The Earth is made up of 4 main layers:– Inner Core– Outer Core– Mantle– Crust

Inner core

Outer core

Mantle

Crust

Structure of the EarthWorking from the center of the Earth out we have:

The inner core is a primarily solid sphere about 1220 km in radius situated at Earth's center.

Based on the abundance of chemical elements in the solar system, their physical properties, and other chemical constraints regarding the remainder of Earth's volume, the inner core is believed to be composed primarily of a nickel-iron alloy, with small amounts of some unknown elements.

Structure of the EarthWorking from the center of the Earth out we have:

The liquid outer core is 2300 km thick and like the inner core composed of a nickel-iron alloy (but with less iron than the solid inner core).

Iseismic and other geophysical evidence indicates that the outer core is so hot that the metals are in a liquid state.

Structure of the EarthWorking from the center of the Earth out we have:

The mantle is approximately 2,900 km thick and comprises 70% of Earth's volume.

This is the largest layer!!

In the mantle, temperatures range between 500-900 degrees Celsius at the upper boundary with the crust to over 4,000 degrees Celsius at the boundary with the core.

The CrustThis is where we live!

The Earth’s crust is made of:

Continental Crust

& Oceanic Crust

The Crust

Continental Crust

Continental crust forms the land (the continents, as the name suggests) that we see today.

Continental crust averages about 35 km thick. Under some mountain chains, crustal thickness is approximately twice that thickness (about 70 km thick).Continental crust is less dense and therefore more buoyant than oceanic crustContinental crust contains some of the oldest rocks on Earth.

The CrustOceanic CrustAs the name already suggests, this crust is below the oceans.Compared to continental crust, Oceanic crust is thin (6-11 km).

It is more dense than continental crust and therefore when the two types of crust meet, oceanic crust will sink underneath continental crust.

The rocks of the oceanic crust are very young compared with most of the rocks of the continental crust. They are not older than 200 million years.

Checkup Quiz:

Move forward when you are ready to test yourself on the

knowledge you gained!

Review song/video of the layers

Checkup Quiz:Which layer is the rigid outer layer of the Earth?

Crust

Asthenosphere

Mantle

Outer core

Inner core

Structure of the Earth

• The Earth is made up of 4 main layers:– Inner Core– Outer Core– Mantle– Crust

Inner core

Outer core

Mantle

Crust

Which layer is the rigid outer layer of the Earth?

Crust

Checkup Quiz:Which layer of the earth is made of

mostly solid metals?

Lithosphere

Asthenosphere

Mantle

Outer core

Inner core

Structure of the EarthVideo

Which layer of the earth is made of mostly solid

metals?

Inner core

Checkup Quiz:Which layer of the earth is made of

mostly liquid metals?

Lithosphere

Asthenosphere

Mantle

Outer core

Inner core

Structure of the EarthVideo

Which layer of the earth is made of mostly solid

metals?

Outer core

Checkup Quiz:Which layer labeled as #5?

Lithosphere

Asthenosphere

Mantle

Outer core

Inner core

Hint: use the scale on the right of the figure!

Structure of the Earth

• The Earth is made up of 4 main layers:– Inner Core– Outer Core– Mantle– Crust

Inner core

Outer core

Mantle

Crust

Which layer labeled as #5?

Outer core

What is Plate Tectonics?

• If you look at a map of the world, you may notice that some of the continents could fit together like pieces of a puzzle.

Plate Tectonics• The Earth’s crust is divided into 12 major

plates which are moved in various directions.• This plate motion causes them to collide, pull

apart, or scrape against each other.• Each type of interaction causes a

characteristic set of Earth structures or “tectonic” features.

• The word, tectonic, refers to the deformation of the crust as a consequence of plate interaction.

World Plates

What are tectonic plates made of?

• Plates are made of rigid lithosphere.

The lithosphere is made up of the crust and the upper part of the mantle.

What are tectonic plates made of?

• Take a look at both labels for lithosphere.

The lithosphere is made up of either type of crust and the upper part of the mantle.

What lies beneath the tectonic plates?

• Below the lithosphere (which makes up the tectonic plates) is the asthenosphere.

Plate Movement• “Plates” of lithosphere are moved around by

the underlying hot mantle convection cells

Plate Movement only need the first :35 sec.

Plate MovementContinental drift is the movement of the Earth's continents relative to each other. The hypothesis that continents 'drift' was first put forward by Abraham Ortelius in 1596 and was fully developed by Alfred Wegener in 1912.

Exercise 1: Wegener

On the back, explain your reasoning on the evidence.

Try to logically piece the continents together so that they form a giant supercontinent. Use the handout in class to use to cut out and paste.

What happens at tectonic plate boundaries?

• Divergent

• Convergent

• Transform

Three types of plate boundary

• Spreading ridges– As plates move apart new material is erupted to

fill the gap

Divergent Boundaries

In plate tectonics, a divergent boundary is a linear feature that exists between two tectonic plates that are moving away from each other. These areas can form in the middle of continents or on the ocean floor.

As the plates pull apart, hot molten material can rise up this newly formed pathway to the surface - causing volcanic activity.Where a divergent boundary forms on a continent it is called a RIFT or CONTINENTAL RIFT, e.g. African Rift Valley.Where a divergent boundary forms under the ocean it is called an OCEAN RIDGE

Age of Oceanic Crust

Courtesy of www.ngdc.noaa.gov

Ocean Ridges: This map shows the age of the oceanic crust. The red coloring shows the youngest ages, whilst the dark blue shows the oldest ages (around 200 million years old).

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ivergent boundaries

• Iceland has a divergent plate boundary running through its middle

Iceland: An example of continental rifting

• There are three styles of convergent plate boundaries– Continent-continent collision– Continent-oceanic crust collision– Ocean-ocean collision

Convergent Boundaries

• Forms mountains, e.g. European Alps, Himalayas

Continent-Continent Collision

Himalayas

Continent-Continent Collision

• Called SUBDUCTION

Continent-Oceanic Crust Collision

Continent-Oceanic Crust Collision

At a convergent boundary where continental crust pushes against oceanic crust, the oceanic crust which is thinner and more dense than the continental crust, sinks below the continental crust.

The oceanic crust descends into the mantle at a rate of centimeters per year

Subduction is a way of recycling the oceanic crust. Eventually the subducting slab sinks down into the mantle to be recycled. It is for this reason that the oceanic crust is much younger than the continental crust which is not recycled.

• Oceanic lithosphere subducts underneath the continental lithosphere

• Oceanic lithosphere heats and dehydrates as it subsides

• The melt rises forming volcanism

• E.g. The Andes

Subduction

• When two oceanic plates collide, one runs over the other which causes it to sink into the mantle forming a subduction zone.

• The subducting plate is bent downward to form a very deep depression in the ocean floor called a trench.

• The worlds deepest parts of the ocean are found along trenches. – E.g. The Mariana Trench is 11 km deep!

Ocean-Ocean Plate Collision

Ocean-Ocean Plate Collision

The subducting plate is bent downward to form a very deep

depression in the ocean floor called a trench.

• Where plates slide past each other

Transform Boundaries

Above: View of the San Andreas transform fault

This map summarizes all the known plate boundaries on Earth, showing whether they are divergent, convergent or transform boundaries

Checkup Quiz :

Move forward when you are ready to test yourself on the

knowledge you gained!

Plate Boundary Rap

Checkup Quiz:Movement of two plates often results a rift valley

is which type of boundary .

ConvergentDivergent Transform

Movement of two plates often results a rift valley

is which type of boundary .

Divergent

Checkup Quiz:Movement of two plates often results in mountains is which type of boundary .

ConvergentDivergent Transform

Movement of two plates often results in mountains is which

type of boundary .

Convergent

Checkup Quiz:Movement of two plates toward each other is

which type of boundary .

ConvergentDivergent Transform

Movement of two plates toward each other is

which type of boundary .

Convergent

Checkup Quiz:Using what you know about the rock cycle,

movement of two plates causing igneous rock is which type of boundary .

ConvergentDivergent Transform

Remember: Igneous rock is formed through the cooling and solidification of magma or lava.

“NEW” rock

Using what you know about the rock cycle, movement of two plates causing igneous rock is which type

of boundary .

Divergent

Checkup Quiz:Using what you know about the rock cycle,

movement of two plates causing metamorphic rock is which type of boundary .

ConvergentDivergent Transform

Metamorphic rocks arise from the transformation of existing rock types, in a process called metamorphism, which means "change in form". The original rock is subjected to heat and pressure, (temperatures greater than 150 to 200 °C and pressures of 1500 bars)

Movement of two plates often results a rift valley

is which type of boundary .

Convergent

Checkup Quiz:Scientists think continental plates move because

of circulating liquid rock below the plates.

True False

Scientists DO think continental plates move because of

circulating liquid rock below the plates.

Plate Tectonics SummaryHow are you doing?

Are you able to describe all of the following?1.Name Earth’s main layers.2.Name and describe three types of plate boundaries.

1.If so, you are ready to move to the next slide!2.If not click on the area you need help with!

Plate Tectonics: Well done! Only one thing left to do:

Turn in your printed Wegener activity with your explanation of the evidence on the back.