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PLATE TECTONIC THEORY BBC - Learning Zone Class Clips - New Zealand - plate tectonics theory - Geography Key concepts: 1. Continental drift 2. Paleomagnetism. CONTINENTAL DRIFT • BBC - Learning Zone Class Clips Investigating the Great Glen Fault – Geography CONTINENTAL DRIFT http://www.wwnorton.com/colleg e/geo/egeo/flash/2_1.swf • Plate tectonics animation • http://videos.howstuffworks.com/search.ph p?media=video&terms=continental+drift More detailed info on continental drift and paleomagnetism • The above concepts led to the theory of SEA FLOOR SPREADING. This then led to the development of SUBDUCTION! All of these need CONVECTION CURRENTS generated in the Earths mantle to work! • HowStuffWorks Videos "100 Greatest Discoveries: Sea Floor Spreading" PLATE MOVEMENT • There are 7 major plates and many more minor plates. As a result of convection currents they move towards, away from or sideways along adjacent plates. It is at these plate boundaries that most of the worlds major landforms occur and where earthquake, volcanoes and mountain building take place. • http://www.as.uky.edu/academics/departments_ programs/EarthEnvironmentalSciences/EarthEn vironmentalSciences/Pages/default.aspx RULES OF PLATE TECTONICS • 1. Continental crust does not sink because of its relatively low density and so it is permanent. Whereas oceanic crust does sink and is continually being formed and destroyed. • 2. Continental plates, such as the Eurasian Plate, may consist of both continental and oceanic crust. • 3. Continental crust may extend far beyond the margins of the landmass. • 4. Plates can not overlap.Either they are pushed upwards to form mountains or downwards into the mantle and destroyed. • 5. No gaps may occur so if plates are moving apart new oceanic crust must be formed. • 6. If new oceanic crust is being formed, elsewhere it must be destroyed. • 7. Plate movement is slow, but usually continuous. • 8. Most significant landforms are at boundaries. Major landforms at plate boundaries. TYPE OF PLATE BOUNDARY CHANGES OCCURING EXAMPLES CONSTRUCTIVE(spreading or divergent) Plates move apart new oceanic crust appears forming midocean ridges with volcanoes. Mid-Atlantic ridge and East Pacific Rise. DESTRUCTIVE (subduction zones, convergent) Oceanic crust moves towards continental crust and being heavier sinks and is destroyed forming deep sea trenches and island arcs with volcanoes. Nazca sinks under South American Plate (Andes) Juan de Fuca sinks under North American Plate (Rockies) Island arcs of the West Indies and Aleutians Indian collided with Eurasian forming Himalayas. African collided with Eurasian forming Alps. COLLISION ZONES 2 continental crusts collide and are forced up into fold mountains. CONSERVATIVE 2 plates move sideways San Andreas fault in past each other. Land is California neither formed or destroyed. Note: centres of plates are a..Shield lands, b. Depressions on edges of the shield. rigid (exception of a rift Canadian shield Amazon. CONSTRUCTIVE MARGINS • 1. OCEANIC PLATES = Mid-Oceanic Ridges. Plates pull apart and new oceanic crust appears. Such as the Mid-Atlantic Ridge and the East Pacific Rise. • 2. CONTINENTAL PLATES = Rift Valleys. Plates pull apart in continental areas, such as East Africa. The Red Sea was formed as a result of this movement. CONSTRUCTIVE PLATE MARGINS • ICELAND Tectonic landforms on Iceland • VOLCANOES: Kerio( see photo), Hekla(signs that eruption is iminent, eruptions every 4-5years). Katla and Eyjafjallajokull(2010 ash eruption, little lava). 36 volcanic systems, fissures up to 500m long, extrude lava. • EARTHQUAKES: 2008 epicentre near Selfoss, 6.6 on R.scale. 40 houses in Selfoss condemned, no fatalities. Fault line unzipping west from Hekla. Several earthquakes occur every day on Iceland. • HOT SPRINGS, MUD POOLS AND GEYSERS:Strokkur geyser(photo), spouts every 4-5 minutes.Blue Lagoon is a geothermal lagoon in the middle of a lava field. • RIFT VALLEY:Thingvellir.(photo)Plates diverging leaving fissures and lava flows. Subsidence of the grabon has created the largest natural lake in Iceland(thingvallavatn). • • BASALT CLIFFS: Vik. Black, basalt beaches.South of Mt. Reynisfjall East African Rift Valley Iceland,s seismic setting. • 2010 eruptions of Eyjafjallajökull Wikipedia, the free encyclopedia • See p.point of Icelandic volcano. • WHY DID THIS HAPPEN? • BBC News - Could another Icelandic volcano erupt soon? DESTRUCTIVE PLATE MARGINS • • • • • • Where 2 plates converge or collide. Oceanic crust can not override continental crust and is forced to dip downwards at an angle to form a subduction zone and its associated deep sea trench. Earthquakes are triggered and heat generated by friction converts the crust back into magma. This is less dense than the mantle and so rises to the earths surface. If it reaches the surface produces volcanoes. Fold mountains are formed or, if offshore Japan or the West Indies, as an island arc. Destructive margin: http://www.classzone.com/books/earth_science/terc/content/visualizations/es0902/es 0902page01.cfm?chapter_no=visualization Fold mountain building: • http://www.classzone.com/books/earth_science/terc/content/visualiz ations/es1105/es1105page01.cfm?chapter_no=visualization • http://videos.howstuffworks.com/science/convergent-plate-boundaries-videosplaylist.htm#video-5933 CONSERVATIVE PLATE BOUNDARY SUMMARY OF PLATE MARGINS. • http://www.classzone.com/books/earth_sci ence/terc/content/visualizations/es0804/es 0804page01.cfm?chapter_no=visualizatio n Types of volcanic material • http://www.classzone.com/books/earth_sci ence/terc/content/visualizations/es0905/es 0905page01.cfm?chapter_no=visualizatio n • Use sheets to discuss the different types of volcanic lava. They have implications for the types of volcanoes produced. HOT SPOTS! • http://www.classzone.com/books/earth_sci ence/terc/content/visualizations/es0904/es 0904page01.cfm?chapter_no=visualizatio n • Video of how they happen! • http://videos.howstuffworks.com/science/h ot-spots-videos-playlist.htm#video-29183