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 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 Asthenosphere Middle Mantle

Vocab p. 38A Definition Example Sentence using Word What it is not

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

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?

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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 BOUNDARIES Type of Boundary Sketch of Boundary Direction of Movement Description/Features of Plate Boundary Examples Diverging Plate Boundary Transform Boundary Conversion Boundary *** Collision Boundary *** 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 boundary Divergent 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 Youngest Crust Oldest Crust

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 other Transform 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 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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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 / 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