Chapter 17 plate tectonics
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Chapter 17 Plate Tectonics. Powerpoint -a-long!. Earth’s Structure (layers of the Earth). The inner core - the solid layer located at the very center of the Earth The outer core - the liquid layer located between the Inner Core and Mantle

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Chapter 17 Plate Tectonics

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Chapter 17 plate tectonics

Chapter 17 Plate Tectonics

Powerpoint-a-long!


Earth s structure layers of the earth

Earth’s Structure (layers of the Earth)

  • The inner core- the solid layer located at the very center of the Earth

  • The outer core- the liquid layer located between the Inner Core and Mantle

  • Mantle- The largest layer of the Earth located above the Outer Core

  • Crust- The outermost layer of the Earth, thickest on land, thinnest on oceans


Crust

Crust

  • Made up of “Tectonic plates”– huge rock slabs that float on the semi fluid mantle

  • Lithosphere– outer layer of the mantle and crust


Continental drift theory

Continental Drift Theory

  • Theory developed Alfred Wegener(1912)

  • States that:

    • Earth’s continents were once all joing into a single landmass called “Pangea”

      • Existed about 200 million years ago (mya)

      • Name means “all the earth” in Greek

    • Continents have moved horizontally to their current locations over a long period of time.

  • Got the idea from “puzzle like” appearance

  • pieces look like they should fit together.


Evidence of continental drift

Evidence of Continental Drift

  • 1.Fossil Clues

    • Mesosaurus: prehistoric freshwater reptile found in S. America and Africa

    • Glossopteris: prehistoric fern found in completely different climates (Africa, Antartica, S. America)


Evidence of continental drift1

Evidence of Continental Drift

  • Rock Clues- Appalachian Mountains similar to mountains in Greenland, S. America mountains similar to ones in Africa


Evidence of continental drift2

Evidence of Continental Drift

  • Sea-floor Spreading – Molten material in the mantle is forced upward

    • Material surfaces at mid-ocean ridges (undersea mountain ranges with steep valleys) in the form of magma. This pushes the continents further apart from each other

    • In some areas, pieces of the crust slip back below the surface and are re-melted.


Evidence of continental drift3

Evidence of Continental Drift

  • 4. Age Evidence– no rocks found on sea floor older than 160 mya

    • Some rocks of continents over 4 Billion years old


Evidence of continental drift4

Evidence of Continental Drift

  • 5. Magnetic Clues– Rocks take on current magnetic properties as they form

    • Iron molecules in the magma “line up” with Earth’s magnetic north and south pole as they cool and crystallize

    • Magnetic Orientation reverses periodically on Earth, and when it does, any rock being laid down show the opposite magnetic orientation

    • Rocks being formed now have “reversed” orientation


Evidence of continental drift5

Evidence of Continental Drift

  • 6.Climatic Evidence –

    • Coal deposits form in swamps when dead plants are buried under mud

      • Antarctica has coal deposits and we’ve found fossils indicating it used to be a temperate swamp

    • Glacial deposits in India, Africa, and Australia indicate that these areas used to be much colder (probably nearer to the poles!)


The plate tectonic theory

The Plate Tectonic Theory

  • The theory of plate tectonics says that:

    • Earth’s crust and rigid upper mantle are broken into enormous slabs called “plates”

    • Tectonic plates move in different directions at different rates over Earth’s surface

    • The plates interact at places called plate boundaries


The plate tectonic theory1

The Plate Tectonic Theory

  • Divergent boundaries: two tectonic plates are moving apart

  • Mostly found on the ocean floor where they form Mid-ocean ridges

  • Lots of Volcanoes, hydrothermal vents, and earthquakes in these areas as magma surge up towards the surface

  • When continental plates separate, it forms a rift valley like that found in Africa


  • The tectonic plate theory

    The Tectonic Plate Theory

    • Convergent boundaries: where two plates are moving towards each other

      • Can be continental-continental, continental-oceanic, or oceanic-oceanic

      • Two possible results:

        • Subduction: one plate slides under the other

          • Creates a deep-sea trench ( Mariana’s Trench – over 6.8 miles deep)

          • Recycles and melts down the crust as it enters the mantle

        • Mountain building: plates push each other upwards to form mountains!

          • Ex. - Himalayas


    The plate tectonic theory2

    The Plate Tectonic Theory

    • Transform Boundary: plates slide horizontally past each other

      • Crust is deformed or fractured (cracked) – lots of earthquakes!

      • Ex. San Andreas Fault


    Causes of plate motions

    Causes of Plate Motions

    • Mantle convection:

      • Convection: transfer of heat energy through the movement of heated matter

        • Heated air or water rises because it is less dense, colder parts sink because they are more dense

      • Heat from the Earth’s core causes magma to rise up towards the crust

      • Cooler parts of the crust sin at convergent boundaries

    • We don’t know if these are permanent or not, how big they are, or how they form


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