Download Plate Tectonics - Madeira City Schools

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8 Grade Science Unit 3 Lesson 3 Theory of Plate Tectonics •  Lithosphere – outermost physical layer •  Asthenosphere – layer immediately below the lithosphere •  The Lithosphere is divided into large, moving pieces – tectonic plates •  Plate Tectonics – explains how the lithosphere plates move around on the slow-­‐ flowing rock of the asthenosphere Properties of Plate Tectonics •  15 major tectonic plates that fit together like a puzzle •  Some sources will divide this into 7 major plates •  Differ in size, shape, density, thickness, and composiLon •  Two Types of lithosphere •  Oceanic Crust – denser and younger rock •  ConLnental Crust – less dense and older Types of Stress •  Tectonic plate movement puts stress on rock •  Stress – amount of force per area put on a body •  DeformaLon – bending, LlLng, and breaking of rock •  Changes the shape and size of features on and below the surface Compression •  Compression-­‐ stress that squeezes or shortens material Tension •  Tension – lengthens a material or pulls a material apart •  Two plates moving away from each other cause tension Shear Stress •  Shear Stress – the rocks will grind past one another in opposite direcLons or at different rates Plate Boundaries •  DeformaLon can occur throughout the plate •  Most deformaLon occurs at places where plates meet •  3 Types of Plate Boundaries •  Convergent Boundary •  Divergent Boundary •  Transform Boundary Convergent Boundary •  Tectonic Plates move toward each other and collide (Compression) •  Ocean Plate – Oceanic Plate (SubducLon Zone) •  Denser plate always sinks beneath the less dense plate •  ConLnental – ConLnental •  Plates push up against one another causing a fold •  Indian Plate and Eurasian Plate Meet •  ConLnental – Oceanic (SubducLon Zone) •  Juan de Fuca and North American Plates Meet Subduction Zone Convergent -­‐ Convergent Juan de Fuca Plate Divergent Boundary •  Two Tectonic Plates moving away from each other (Tension) •  As the lithosphere moves apart – the lithosphere thins •  Thinning allows the lithosphere to rise to the surface and melt •  MelLng produces magma which moves to the Earth’s surface (where it cools and solidifies) •  North American Plate and Eurasian Plate (Mid AtlanLc Ridge) Fault Block Mountains Transform Boundary •  Forms when two boundaries move horizontally past one another •  The plates slowly scrape against one another causing energy to build •  Shi\ suddenly releasing energy – Earthquake •  San Andreas Fault – Transform Boundary •  North American plate and Pacific Plate •  Most studied transform boundary in the world Features of Convergent Boundaries Two Huge Convergent Boundary Concepts •  Huge Mountains form along convergent boundaries •  SubducLon Zones are associated with volcanic acLvity Folded Mountains •  Folded Mountains – two conLnental lithospheric plates converge •  Plates tend to be pushed upward and folded and faulted. •  Appalachian Mountains •  Himalayas Volcanoes •  Oceanic and Con+nental Plates Collide – the oceanic plate subducts undernearth •  Magma rises to the surface •  Over Lme a chain of volcanic mountains form •  Cascade Mountains •  Ex. Juan de Fuca Plate and the North American Plate •  Also Volcanoes can form from subducLng oceanic plates called a volcanic island arc •  Philippine Islands Ocean Trenches •  Ocean Trenches are the deepest landforms found on the ocean floor •  Volcanic Island Arcs form parallel to Ocean Trenches •  Deepest Trench is the Mariana Trench Divergent Boundaries •  Most divergent boundaries are found on the Sea Floor •  Fault-­‐Block Mountains •  Form when block of lithosphere drop down or are li\ed up along faults •  Grand Teton Mountains •  Ri\s •  Long, narrow, faulted ri\ valleys •  Ri\ Zones – areas with many long, deep cracks in Earth’s Lithosphere •  When this happens on the ocean floor – forms Mid-­‐ Ocean Ridges Transform Boundaries •  Caused from Shear Stress •  Rocks on either side of the boundary grind past one another •  The rocks will break if the shear stress is great enough •  When rocks suddenly break along these Faults – Earthquakes happen Hot Spots •  Hot Spot – magma rises from deep within Earth through the lithosphere to reach the ocean floor •  Over Lme, lava flows build up to form an undersea volcano unLl it reaches the surface forming a volcanic island •  Over Lme, new oceanic lithosphere is posiLoned over the hot spot •  Hawaiian Island •  The newest Islands in the island chain are closer to the hot spot.