1. What might have made this huge crack?2. How could this crack (over time ) change the landscape of the Earth’s surface?

Discovery Ed.

The Structure of the Earth and Plate Tectonics

Structure of the Earth• The Earth is

made up of 4 main layers:– Inner Core– Outer Core– Mantle– Crust

The Crust• This is where we live!• It is thin, very hard and brittle• The Earth’s crust is divided

into two types.

Continental Crust- Forms the land-thick (10-70km)- buoyant (less dense than oceanic crust) - mostly old

Oceanic Crust- Ocean floor-thin (~7 km)- dense (sinks under continental crust)- young

Label This

Continental Crust

Oceanic CrustOceanic Crust

Sublevels Lithosphere – the crust and the very top of the mantle makes this zone of rigid, brittle rock

Asthenosphere – a layer of hot soft semi-rigid rock in the middle mantle thatflows

Label This

Upper Mantle

Lower Mantle

Convection Currents

Lithosphere

AsthenosphereMiddle Mantle

Vocab p. 38A

Definition Example

Sentence using Word

What it is not

Inner Core

A hot solid ball ofmetal that is the Inner most part of the Earth.

Example

The inner core is the most dense layer of the Earth

Outer surfaceLiquidcold

Warm Up• Get a Textbook and turn to page

15A. Look at the picture.

• What do you think the shaded area on the outline maps of South America and Africa represent?

What is Plate Tectonics?

Generally Speaking

The theory of plate tectonics explains how the Earth’s surface has changed over geologic time.

The Earth’s outer crust is made of plates of rock that continues to shift and collide resulting in earthquakes and volcanoes, mountain ranges, rift valleys, etc…

What are the specifics of Plate Tectonics?

• The Earth’s crust is divided into 12 major plates which move 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.

What causes the plates to move?

How and Why do Tectonic Plates move around?

\

What are convection currents?

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

the underlying hot mantle convection cells. Hot magma rises and cools then fall back toward the core.

What are tectonic plates made of?

What lies beneath the tectonic 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 lies beneath the tectonic plates?

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

Where are the World Plates located?

World Plates

• 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.

Warm Up• Read Evidence for Continental Drift on

pg.15A and answer the following:

1. List the 3 pieces of evidence used to prove continental drift?

2. Which evidence do you think is the most convincing and explain your answer?

Practical Exercise 1

Supercontinents!

• What are supercontinents?

• How do they form and how do they break apart?

What are supercontinents? a landmass comprising more than one continental core, or craton. How do they form and how do they

break apart? Through continental collision fewer and

larger continents are formed while rifting makes more and smaller continents.

What happens at tectonic plate boundaries?

TYPES OF PLATE BOUNDARIESType ofBoundary

Sketch ofBoundary

Direction ofMovement

Description/Features of Plate Boundary

Examples

DivergingPlateBoundary

TransformBoundary

ConversionBoundary***Collision

CollisionBoundary***Subduction

Ocean-Ocean

Ocean-Continent

Ocean-Ocean

Ocean-Continent

Ocean-Ocean

Ocean-Continent

Ocean-Ocean

Ocean-Continent

Divergent Boundaries

• Spreading ridges ex. Mid-ocean ridge– As plates move apart new material is erupted to fill the gap

Divergent Boundaries

Three types of plate boundaryDivergent boundaries are where plates move away from each other

• Iceland has a divergent plate boundary running through its middle

Iceland: An example of continental rifting

Age of Oceanic Crust

Courtesy of www.ngdc.noaa.gov

Youngest Crust

Oldest Crust

Transform Boundaries

Transform Boundaries

The San Andreas fault, adjacent to which the US city of San Francisco is built is an example of a transform boundary between the Pacific plate and the North American plate.

• Where plates slide past each otherTransform Boundaries

Above: View of the San Andreas transform fault

Convergent Boundaries

the plates move towards each other

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

Convergent Boundaries

Continent-Continent Crust Collision

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

Continent-Continent Crust Collision

Continent-Oceanic Crust Collision

Occurs along Continent-Oceanic collision and Ocean-ocean collision•

SUBDUCTION Zones

• 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 collision

TYPES OF PLATE BOUNDARIESType ofBoundary

Sketch ofBoundary

Direction ofMovement

Description/Features of Plate Boundary

Examples

DivergingPlateBoundary

plates move away from each other

Mid-Ocean Ridge

TransformBoundary

plates slide past each other

The San Andreas fault

ConversionBoundary***Collision

plates move towards each other

CollisionBoundary***Subduction

Ocean-Ocean

Ocean-Continent

Ocean-Ocean

Ocean-Continent

Ocean-Oceantwo oceanic plates collide one rolls on top while pushing the other into the mantelOcean-ContinentContinent plate collides with Oceanic plate. CP rolls on top of the more dense OP

Ocean-OceanMariana Trench

Ocean-Continentmany volcanoesAndes mountain

• end

• Divergent

• Convergent

• Transform

Three types of plate boundary

Himalayas

Practical Exercise 2

Where will the UK be in:1,000 years?1,000,000 years?1,000,000,000 years?

…what’s the connection?

Volcanoes and Plate Tectonics…

Volcanism is mostly focused at plate margins

Pacific Ring of Fire

- Subduction - Rifting - Hotspots

Volcanoes are formed by:

Pacific Ring of Fire

Hotspot volcanoes

• Hot mantle plumes breaching the surface in the middle of a tectonic plate

What are Hotspot Volcanoes?

Photo: Tom Pfeiffer / www.volcanodiscovery.com

The Hawaiian island chain are examples of hotspot volcanoes.

The tectonic plate moves over a fixed hotspot forming a chain of volcanoes.

The volcanoes get younger from one end to the other.

• As with volcanoes, earthquakes are not randomly distributed over the globe

• At the boundaries between plates, friction causes them to stick together. When built up energy causes them to break, earthquakes occur.

Figure showing the distribution of earthquakes around the globe

Where do earthquakes form?

Figure showing the tectonic setting of earthquakes

Plate Tectonics Summary• The Earth is made up of 3 main layers (core,

mantle, crust)• On the surface of the Earth are tectonic

plates that slowly move around the globe• Plates are made of crust and upper mantle

(lithosphere)• There are 2 types of plate• There are 3 types of plate boundaries• Volcanoes and Earthquakes are closely

linked to the margins of the tectonic plates

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

asthenosphere

• Spreading ridges– As plates move apart new material is

erupted to fill the gap

Divergent Boundaries