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Chapter 14.3: The Theory of Plate Tectonics

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8th Grade Integrated Science chapter 14 lesson 3 on the theory of plate tectonics. This lesson covers plate boundaries and the effects of the movement. It includes pictures and definitions of divergent, convergent, transform, collision, and subduction boundaries. There is an explanation of the lithosphere and the asthenosphere including convection currents. This also introduces forces causing plate motion such as basal drag, ridge push, and slab pull.

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Chapter 14.3: The Theory of Plate Tectonics

1. 1. Chapter 14 Lesson 3: The Theory of Plate Tectonics – p510-519 - page1 Vocabulary  Plate tectonics (511) – Earth’s surface is made of rigid slabs of rock, or plates, that move with respect to each other  Lithosphere (512) – the cold and rigid outermost rock layer  Divergent plate boundary (513) – forms where two plates separate  Transform plate boundary (513) – Forms where two plates slide past each other  Convergent Plate Boundary (513) – form where two plates collide  Subduction (513) – A process in which the denser plate sinks below the more buoyant plate  Convection (516) – the circulation of material caused by differences in temperature  Ridge Push (517) – the forces that causes rising mantle material at mid-ocean ridges that creates the potential for plates to move away from the ridges  Slab Pull (517) – As a slab sinks, it pulls on the rest of the plate with this force The Plate Tectonic Theory  Earth’s crust is constantly being __________________ and destroyed  The ______________________ of plate tectonics states that Earth’s surface is made of rigid slabs of rock, or plates, that move with respect to each other  Each plate moves over Earth’s hot and ______________________________ mantle o The term _________________________ describes the forces that shape Earth’s surface and the resulting rock structures o Plate tectonics is used to explain ______________________and volcanic eruptions Tectonic Plates
2. 2. Chapter 14 Lesson 3: The Theory of Plate Tectonics – p510-519 - page2 Tectonic Plates  The Pacific Plate is the ______________________ plate  The Juan de Fuca is one of the ________________________  The boundaries that run through oceans mark the positions of the ____________________________ ridges  Earth’s outermost layers are cold and rigid compared to the layers in Earth’s interior. It is called the__________________________________________. o It is made up of the crust and the solid, uppermost _______________________. o It is ____________ below ocean ridges and __________________ below continents o The tectonic plates are just large pieces of the ________________________.  Just ___________________ the lithosphere is called the asthenosphere. o This layer is so hot that it behaves like a _____________________ material o This enables to lithosphere to ___________________ Plate Boundaries
3. 3. Chapter 14 Lesson 3: The Theory of Plate Tectonics – p510-519 - page3 Divergent Plate Boundaries  Mid-ocean ridges are located along _______________________ plate boundaries.  A divergent plate boundary forms where two plates __________________  When the seafloor spreads at a mid-ocean ridge, lava erupts, cools, and forms new __________________ crust.  Divergent plate boundaries can also exist in the ______________________of a continent o They pull continents apart and form rift ______________________ o The East African Rift is an example. Transform Plate Boundaries  A transform plate boundary forms where two plates _________________past each other. o The San Andrews Fault in California is a well known example. o As the plates move past each other, they can get stuck and _____________moving, o ________________________builds up where the plates are stuck. o Eventually the stress is too great and the rocks _________________ o The resulting rapid energy release is an________________________. San Andreas Fault Convergent Plant Boundaries
4. 4. Chapter 14 Lesson 3: The Theory of Plate Tectonics – p510-519 - page4  Convergent plate boundaries form where two plates ______________________  The ________________________ plate sinks below the more buoyant plate in a process called subduction o The area where a denser plate descends into Earth is called a ________________________ zone.  When an oceanic plate and continental plate collide the denser oceanic plate subducts under the edge of the _______________________. o This creates a deep ocean trench o A line of ______________________ forms above the subducting plate on the edge of the continent  This process can also happen with two oceanic plates. o Typically the older, denser plate will subduct beneath the _____________________ plate. o This creates a deep ocean trench and a line of volcanoes called an ______________ arc  When two continental plates collide, neither plate is subducted. o Instead rock is uplifted and create mountains like the Himalayas
5. 5. Chapter 14 Lesson 3: The Theory of Plate Tectonics – p510-519 - page5 Evidence for Plate Tectonics  Continents move apart or come together at speeds of a few _______________ per years  Today scientists use a network of ______________________ called the Global Positioning System (GPS) to measure the movement of the plates  The theory of plate tectonics explains why earthquakes and volcanoes occur in certain ___________________.  All types of plate boundaries can result in _________________________ due to the rapid release of energy  Diverging and _______________________ plates result in volcanoes  __________________________ form when two continental plates converge
6. 6. Chapter 14 Lesson 3: The Theory of Plate Tectonics – p510-519 - page6 Plate Motion  Convection Currents o Convection is the ________________________of material caused by differences in temperature and density  For example, the upstairs floors of most houses often warmer than the lower floor  This is because warm air ________________ while denser, cold air sinks.  Tectonic plate activity is related to convection in the__________________ . o ________________________________ elements heat Earth’s interior. o When materials such as solid rock are heated, they expand and become less ______________. o Hot mantle material rises upward and comes in contact with Earth’s ____________. o Thermal energy is _________________________ to the surface o As the mantle__________________ , it becomes denser and then sinks, forming a convection current  These currents in the ____________________________ act like a conveyor belt moving the lithosphere. Forces causing plate motion o Scientists are still _______________ about which force has the greatest influence. Basal Drag o This is when convection currents in the asthenosphere move or drag the _______________________ much like how walking sidewalks at the airport move people.
7. 7. Chapter 14 Lesson 3: The Theory of Plate Tectonics – p510-519 - page7 Ridge Push o Recall that mid-ocean ridges have greater _____________________ than the surrounding seafloor. o Because they are higher, ___________________ pulls the surrounding rock down and away from the ridge o Rising mantle material at mid-ocean ridges creates the _____________________ for plates to move away from the ridge with a force called ridge push.  This moves the lithosphere _______________ from the mid-ocean ridge. Slab Pull o When plates converge, the _________________ plate will sink into the mantel along a subduction zone o This plate is called a____________________. It is usually old and cold which makes it denser. o As a slab sinks, it ____________ on the rest of the plate with a force called slab pull. A Theory in Progress  Plate tectonics has become the ________________________ theory of geology  It explains the connection between continental drift and the __________________ and destruction of crust along plate boundaries. o `It also helps to explain the occurrence of earthquakes, volcanoes, and mountains Unanswered Questions  Several questions remain unanswered: o Why is Earth the only ______________ in the solar system that has plate tectonic activity? o Why do some earthquakes and volcanoes occur far away from plate boundaries?  Part of the answer has to do with plate thickness. The other part is the scientists are still learning how active the mantle really is. o What forces _________________________ plate motion?