Presentation on theme: "The Theory of Plate Tectonics"— Presentation transcript:
1The Theory of Plate Tectonics Terms:J. Tuzo WilsonPlateScientific theoryPlate tectonicsFaultDivergent boundaryRift valleyConvergent boundaryTransform boundaryConcepts:What is the theory of plate tectonics?What are the three types of plate boundaries?
2J. Tuzo Wilson and Plates A Canadian scientist, J. Tuzo Wilson, observed that there are cracks in the continent similar to those on the ocean floor.In 1965, Wilson proposed a new way of looking at these cracks.According to Wilson, the lithosphere is broken into separate sections called plates.
3Lithospheric PlatesThe plates fit together along cracks in the lithosphere . The plates carry the continents or parts of the ocean floor or both. Wilson combined what geologists knew about sea-floor spreading, Earth plates, and continental drift into a single theory.What is a scientific theory? It is a well tested concept that explains a wide range of observations.
4The Theory of Plate Tectonics The theory of plate tectonics explain the formation, movement, and subduction of Earth’s plates.
5How do the plates move?The theory of plate tectonics states that pieces of Earth’s lithosphere are driven by convection currents in the mantle.As the plates move, they collide, pull apart, or grind past each other producing spectacular changes in Earth’s surface.Volcanoes, mountain ranges, and deep ocean trenchesThe plates move very slow about 1-24 centimeters a year.About as fast as your fingernails grow.They have been moving for tens of millions of years.
6The result of plate movements can result in catastrophic events.
7Plate movement also creates beautiful landscapes https://www.google.com/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&docid=icN9y-7uTUhWrM&tbnid=aKKasg5R-vQHtM:&ved=0CAQQjB0&url=http%3A%2F%2Fwww.igf.fuw.edu.pl%2Fhill%2Fashima.html&ei=dJWBUtLQKsKqiQKL9YCgAw&bvm=bv ,d.cGE&psig=AFQjCNG1IWSWUDEdF1Vnur3ZQLCjtsEX-Q&ust=
8What action occur at each location/type of plate boundary? As we review each plate boundary, complete a tree map and include the following:Focus Questions:Plate BoundaryWhich direction are the plates moving at these boundaries in relationship to each other?What action occur at each location/type of plate boundary?What forms because of these actions?Examples
10Types of plate boundaries Divergent plate boundaryOcean: Mid Oceanic RidgeLand: Continental Rift zoneConvergent plate boundaryOceanic-oceanic convergence – Subduction TrenchContinental-continental convergence – No Subduction - MountainsOceanic - continental convergence – Subduction TrenchTransform plate boundaryEarthquakesCrust is neither created nor destroyed.The place where two plates move apart, or diverge, is called a divergent boundary. Most divergent boundaries occur along the mid-ocean ridges, where sea-floor spreading occurs.Divergent boundaries also occur on land, two of Earth’s plates slide apart. A deep valley called a rift valley forms along the divergent boundary. For example the Great Rift Valley in East Africa marks a deep crack in the African continent.Convergent boundary is the place where two plates come together, or converge. When two plates collide, the density of the plates determines which one comes out on top.Oceanic crust becomes cooler and denser as it spreads away from the mid ocean ridge. Where tow plates carrying ocreanic crust meet at a trench, the plate that ismore dense sinks under the other plate.Sometimes a plate carrying oceanic crust collides with a plate carrying continental crust. Oceanic crust is more dense than continental crust. The less dense continental crust can’t sink under the more dense oceanic crust. Instead subduction occurs as the oceanic plate sinks beneath the continenal plate.When two plates carrying continental crust collide, subduction doesn’t take place but mountains form.Transform boundaries is a place where tow plates slip past each other, moving in opposite directions. Earthquakes often occure along transform boundaries, but crust is neither created or destroyed.
11Divergent plate boundaries A place where two plates move apart, or diverge
12OceanMid-Ocean Ridge E.g. Mid-Atlantic ridge is a result of sea floor spreadingnew basaltic magma rises to the surface along the ridge forming new oceanic crust.
13Thingvellir Rift Valley Slicing through the center of Iceland is the Mid-Atlantic Ridge. This is the boundary between theNorth American and Eurasian tectonic platesThingvellir National Park, in southwestern Iceland, is one of the few spots in the world where an underwater ridge rises above the water surface.Iceland is one of the most geologically active places on Earth with more than 15 volcanoes that have erupted in the last century.
14Rift valleys may increase in size till water fills them to form a Sea LandRift valleys may increase in size till water fills them to form a SeaThe Red Sea and the Gulf of Aden were once rift valleys.Mt. KilimanjaroThese rift valleys often have volcanoes lining them.Great African Rift Valley
15The formation of the Atlantic Ocean The Atlantic Ocean was also a result of a land rift!
16Divergent Plate Boundaries In the OceanRidgeAction: oceanic plates move apartSea floor spreadingMid-Ocean RidgeExample: Mid Atlantic RidgeLongest mountain RangeOn LandRiftAction: Continental crust pull apartExamples: Iceland, Great Rift Valley in East AfricaOceans and Seas formExample: Atlantic Ocean and Red SeaVolcanoesExample: Mt. KilimanjaroIn groups – compare and discuss peer maps.What’s the difference between a ridge and a rift?
17Tree Map Divergent Plate Boundary Plate Movement Ocean: Ridge Land: RiftAction: Sea-floor spreadingExample: Mid Atlantic RidgeOceans and Seas form:Examples: Atlantic Ocean and the Red SeaAction: Continental crust pull apartExamples: Iceland, Great Rift Valley in East AfricaOceans and Seas formExample: Atlantic Ocean and Red SeaVolcanoesExample: Mt. KilimanjaroA place where to plates move apart, or diverge
18Convergent Plate Boundaries The place where two plates come together, or converge.Three types of convergent plate boundaries:Ocean crust to ocean crust collisionOcean crust to continental crust collisionContinental crust to continental crust collisionMake predictions as to what each of these collisions will form.
19Tree Map Name of plate boundary Draw arrows to indicate direction the plates move in relationship to each other.Create a Tree map of the 3 types of convergent boundaries, the events that occur there, and an example of each occurrence. i.e. action, formations, examplesCompare the items in your map, which convergent boundary type does NOT result in volcanoes? Why?
23Oceanic - continental convergence E.g. Andes mountainsThe forces of plate tectonics are responsible for the formation of the Andes. The Nazca plate and a part of the Antarctic plate have been subducting beneath the South American plate, which is a process that continues today and causes earthquakes andvolcanic eruptions in the region
29Convergent Boundaries 3 types of convergent boundariesOcean to ocean crustCrust melting forms volcanic island arc, ex Aleutian IslandsVolcanoes – Philippines- Mt PinatuboSubduction forms trenchOcean to continental crustCrust melting forms volcanic mountain ranges, ex Andes, cascade range, Mt Rainer, Mt BakerSubduction zones forms, trenches,Ocean crust denser than continental crust.Ocean crust slides/subducts under the continental crustContinental to continental crustNo melting of crust = no volcanoesNo subductionFolding of crust = Non-volcanic mountains are formed -Example Mt Everest
30Tree Map Convergent Plate Boundaries Ocean to ocean crust Continental to continental crustOcean to ocean crustOcean to continental crustCrust melting forms volcanic mountain ranges, ex Andes, cascade range, Mt Rainer, Mt BakerSubduction zones forms trenchesOcean crust denser than continental crust.Ocean crust slides/subducts under the continental crustCrust melting forms volcanic island arc, ex Aleutian IslandsVolcanoes – Philippines- Mt PinatuboSubduction forms trenchesNo melting of crust = no volcanoesNo subductionFolding of crust = Non-volcanic mountains are formed-Example Mt Everest
31Transform BoundaryA place where two plates slip past each other, moving in opposite directions
35Transform plate boundary Action: EarthquakesForms: faultExample: San Andres faultNo crustal melting = No volcanoes
36Transform BoundaryDraw arrows to indicate direction the plates move in relationship to each other.Name a location of a transform boundary.Name the event that occurs at transform boundaries.Could a volcano erupt in Los Angeles? Why or why?
37No crustal melting = No volcanoes Transform BoundaryCrust is neither created nor destroyedFormsDirectionFaultsNo crustal melting = No volcanoesEarthquakesIs a place where two plates slip past each otherExample: San Andres fault