plate tectonics

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The Structure of the Earth and Plate Tectonics : 

The Structure of the Earth and Plate Tectonics

Structure of the Earth : 

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

The Crust : 

The Crust This is where we live! The Earth’s crust is made of: Continental Crust thick (10-70km)- buoyant (less dense than oceanic crust) - mostly old Oceanic Crust - thin (~7 km)- dense (sinks under continental crust)- young

How do we know what the Earth is made of? : 

How do we know what the Earth is made of? Geophysical surveys: seismic, gravity, magnetics, electrical, geodesy Acquisition: land, air, sea and satellite Geological surveys: fieldwork, boreholes, mines

What is Plate Tectonics? : 

What is Plate Tectonics?

Slide 6: 

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.

Slide 7: 

Alfred Wegener

Slide 8: 

Alfred Wegener – proposed that in the distant past, the Earth’s continents were all joined as a single landmass. -South America and Africa would fit remarkably well, shoreline to shoreline. -If the Americas were moved next to Africa and Europe, there would be a match of ancient continental rocks and tectonic (fold and fault) structures. -Pangaea – when Wegener placed all the continents together like a puzzle, it formed a large landmass which he called Pangaea.

Slide 9: 

Pangaea Puzzle!

Plate Tectonics : 

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 : 

World Plates

What are tectonic plates made of? : 

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? : 

What lies beneath the tectonic plates? Below the lithosphere (which makes up the tectonic plates) is the asthenosphere.

Plate Movement : 

Plate Movement “Plates” of lithosphere are moved around by the underlying hot mantle convection cells

What happens at tectonic plate boundaries? : 

What happens at tectonic plate boundaries?

Slide 16: 

Divergent Convergent Transform Three types of plate boundary

Slide 17: 

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

Slide 18: 

Age of Oceanic Crust Courtesy of www.ngdc.noaa.gov

Slide 19: 

Iceland has a divergent plate boundary running through its middle Iceland: An example of continental rifting

Slide 20: 

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

Slide 21: 

Forms mountains, e.g. European Alps, Himalayas Continent-Continent Collision

Slide 22: 

Himalayas

Slide 23: 

Called SUBDUCTION Continent-Oceanic Crust Collision

Slide 24: 

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

Slide 25: 

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

Slide 27: 

Where plates slide past each other Transform Boundaries Above: View of the San Andreas transform fault

Slide 29: 

Practical Exercise 2 Where will the UK be in: 1,000 years? 1,000,000 years? 1,000,000,000 years?

Slide 30: 

…what’s the connection? Volcanoes and Plate Tectonics…

Slide 31: 

Volcanism is mostly focused at plate margins Pacific Ring of Fire

Slide 32: 

- Subduction - Rifting - Hotspots Volcanoes are formed by:

Slide 33: 

Pacific Ring of Fire Hotspot volcanoes

Slide 34: 

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.

Slide 35: 

The tectonic plate moves over a fixed hotspot forming a chain of volcanoes. The volcanoes get younger from one end to the other.

Slide 36: 

…what’s the connection? Earthquakes and Plate Tectonics…

Slide 37: 

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? : 

Where do earthquakes form? Figure showing the tectonic setting of earthquakes

Plate Tectonics Summary : 

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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