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Chapter 13The Structure of the Earth and

Plate Tectonics

Structure of the Earth3 main layers:• Core (inner + outer)

• Mantle• Crust Inner core

Outer core

Mantle

Crust

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Continental Crust- thick (10-70km)- buoyant (less dense) - mostly old

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

The Crust

More details to follow in Chapter 15S.3

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How do we know what the Earth is made of?

• Geophysical surveys: seismic, gravity, magnetic, electrical, geodesy

• Acquisition: land, air, sea and satellite• Geological surveys: fieldwork, boreholes, mines

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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.

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World Plates What are tectonic plates made of?

Plates are made of rigid lithosphere.

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

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What lies beneath tectonic plates?Below the lithosphere is the asthenosphere.

The asthenosphere, is the molten part of the upper mantle.

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

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Exercise 1

Supercontinents!The Pangaea Puzzle

Note: DO NOT overlap edges.

What happens at tectonic plate boundaries?

• Divergent

• Convergent

• Transform

Three Types of Plate Boundaries

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

fill the gap.

Divergent Boundaries

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Age of Oceanic Crust

Courtesy of www.ngdc.noaa.gov

Age of Oceanic Crust

Courtesy of www.ngdc.noaa.gov

Seafloor Spreading and Magnetic Reversals

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There are three styles of convergent plate boundaries• Continent-Continent collision• Continent-Oceanic Crust collision• Oceanic-Oceanic Crust collision

Convergent Boundaries

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• FORMS MOUNTAIN RANGES(e.g. European Alps, Himalayas)

Continent-Continent Collisions

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India + Eurasia = The Himalayas

• Results in SUBDUCTION ZONES

Continent-Oceanic Crust Collisions

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• Oceanic lithosphere subductsunderneath the continental lithosphere

• Oceanic lithosphere heats and dehydrates as it subsides

• The melt rises forming volcanoes

• e.g. Andes, Cascades

Subduction

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• one plate runs over the other which causes it to sink into the mantle forming a subduction zone.

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

• deepest parts of the ocean found along trenches. – Mariana Trench is 11 km deep– Mount Everest is only 8 km high.

Ocean-Ocean Plate Collision

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Ocean-Ocean Plate Collision

Mariana Trench vsMt. Everest

• Where plates slide past each otherTransform Boundaries

Above: View of the San Andreastransform fault

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Exercise 1

Supercontinents!The Pangaea Puzzle

Note: DO NOT overlap edges.

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Exercise 2

Plate Motion!• Label the Tectonic Plates Map• Show the relative motion of each plate.

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UNIT TEST - Chapters 13-16

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Assignments:Chapter 13 – Plate Tectonics Notes & Vocab √Chapter 14 – Plate Tectonics & Volcanoes Notes & VocabChapter 15 – Plate Tectonics & Earthquakes Notes & VocabChapter 16 – Plate Tectonics & Mountain Building Notes & Vocab

For Review and Test Prep:Go to esc11.weebly.com

• Flashcard Library (home page)• volcano photo review• link to practice quizzes and review PowerPoints• Quizlab – Chapters 13-16 Practice Test