1. What might have made this huge crack?

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1. What might have made this huge crack? 2.
How could this crack (over time ) change the
landscape of the Earths surface?
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Discovery Ed.
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The Structure of the Earth and Plate Tectonics
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Structure of the Earth

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

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The Crust

• This is where we live!
• It is thin, very hard and brittle
• The Earths 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

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Label This
Continental Crust
Oceanic Crust
Oceanic Crust
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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
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Label This
Lithosphere
Upper Mantle
Convection Currents
Lower Mantle
Asthenosphere
Middle Mantle
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Vocab p. 38A
Definition
Example
Sentence using Word
What it is not
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Inner Core
A hot solid ball of metal that is the Inner most
part of the Earth.
Example
The inner core is the most dense layer of the
Earth
Outer surface Liquid cold
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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?

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What is Plate Tectonics?
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Generally Speaking
The theory of plate tectonics explains how the
Earths surface has changed over geologic time.
The Earths outer crust is made of plates of
rock that continues to shift and collide
resulting in earthquakes and volcanoes, mountain
ranges, rift valleys, etc
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What are the specifics of Plate Tectonics?

• The Earths 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.

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• What causes the plates to move?

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How and Why do Tectonic Plates move around?
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What are convection currents?
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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.

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What are tectonic plates made of?
What lies beneath the tectonic plates?
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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.
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What lies beneath the tectonic plates?

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

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Where are the World Plates located?
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World Plates
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• 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.

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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?

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Practical Exercise 1

• Supercontinents!

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• What are supercontinents?
• How do they form and how do they break apart?

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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.

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What happens at tectonic plate boundaries?
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TYPES OF PLATE BOUNDARIES
Type of Boundary Sketch of Boundary Direction of Movement Description/Features of Plate Boundary Examples
Diverging Plate Boundary
Transform Boundary
Conversion Boundary Collision
Collision Boundary Subduction Ocean-Ocean Ocean-Continent Ocean-Ocean Ocean-Continent Ocean-Ocean Ocean-Continent Ocean-Ocean Ocean-Continent
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Divergent Boundaries
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Divergent Boundaries

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

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Three types of plate boundary
Divergent boundaries are where plates move away
from each other
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Iceland An example of continental rifting

• Iceland has a divergent plate boundary running
  through its middle

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Age of Oceanic Crust
Youngest Crust
Oldest Crust
Courtesy of www.ngdc.noaa.gov
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Transform Boundaries
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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.
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Transform Boundaries

• Where plates slide past each other

Above View of the San Andreas transform fault
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Convergent Boundaries
the plates move towards each other
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Convergent Boundaries

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

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Continent-Continent Crust Collision
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Continent-Continent Crust Collision

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

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Continent-Oceanic Crust Collision
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SUBDUCTION Zones

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

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Subduction

• Oceanic lithosphere subducts underneath the
  continental lithosphere
• Oceanic lithosphere heats and dehydrates as it
  subsides
• The melt rises forming volcanism
• E.g. The Andes

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Ocean-Ocean Plate Collision

• 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!

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Ocean-ocean collision
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TYPES OF PLATE BOUNDARIES
Type of Boundary Sketch of Boundary Direction of Movement Description/Features of Plate Boundary Examples
Diverging Plate Boundary plates move away from each other Mid-Ocean Ridge
Transform Boundary plates slide past each other The San Andreas fault
Conversion Boundary Collision plates move towards each other
Collision Boundary Subduction Ocean-Ocean Ocean-Continent Ocean-Ocean Ocean-Continent Ocean-Ocean two oceanic plates collide one rolls on top while pushing the other into the mantel Ocean-Continent Continent plate collides with Oceanic plate. CP rolls on top of the more dense OP Ocean-Ocean Mariana Trench Ocean-Continent many volcanoes Andes mountain
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• end

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Three types of plate boundary

• Divergent
• Convergent
• Transform

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Himalayas
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Practical Exercise 2
Where will the UK be in 1,000 years? 1,000,000
years? 1,000,000,000 years?
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Volcanoes and Plate Tectonics

• whats the connection?

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Pacific Ring of Fire
Volcanism is mostly focused at plate margins
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Volcanoes are formed by

• - Subduction - Rifting - Hotspots

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Pacific Ring of Fire
Hotspot volcanoes
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What are Hotspot Volcanoes?

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

The Hawaiian island chain are examples of hotspot
volcanoes.
Photo Tom Pfeiffer / www.volcanodiscovery.com
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The tectonic plate moves over a fixed hotspot
forming a chain of volcanoes.
The volcanoes get younger from one end to the
other.
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• 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
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Where do earthquakes form?
Figure showing the tectonic setting of earthquakes
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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

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Structure of the Earth
asthenosphere

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

Mantle
Outer core
Inner core
Crust
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Divergent Boundaries

• Spreading ridges
• As plates move apart new material is erupted to
  fill the gap