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Plate Tectonics

Plate Tectonics. How did it form to the current day earth?. EARTH; once upon a time. http://www.classzone.com/books/earth_science/terc/content/visualizations/es0806/es0806page01.cfm?chapter_no=visualization. Tectonics Plates.

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Plate Tectonics

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  1. Plate Tectonics

  2. How did it formto the current day earth? EARTH; once upon a time http://www.classzone.com/books/earth_science/terc/content/visualizations/es0806/es0806page01.cfm?chapter_no=visualization

  3. Tectonics Plates • Earth’s crust is now broken to several pieces called crustal or tectonic plates • Each plate has an average thickness of 100km and is composed of both continental and oceanic crust • Plate movement results in various landform appearance

  4. Tectonics Plates • 9 major plates have been identified: • Eurasian plate • Philippine plate • Indo-Australian plate • Pacific plate • North American plate • African plate • South American plate • Nazca plate • Antarctic plate

  5. Causes of Plate Movements • Convection currents in the athenosphere • Currents circulate near the base of the lithosphere, cause drag on the bottom of the plates, causing them to move over the surface of the Earth. http://www.classzone.com/books/earth_science/terc/content/visualizations/es0805/es0805page01.cfm?chapter_no=visualization

  6. Plate movements and boundaries • As the plates move, they interact with each other at their boundaries. • 3 types of boundaries: • Divergent Plate Boundaries • Convergent Plate Boundaries • Transform Fault Boundaries

  7. Plate movements and boundaries • Divergent Plate Boundaries

  8. Plate movements and boundaries • Convergent Plate Boundaries

  9. Plate movements and boundaries • Transform Fault Boundaries

  10. Divergent Plate Boundaries • Zones of Tension • Occurs mostly beneath oceans, few occur within continents • Convection currents diverge (moving apart), the plates are pulled apart • Magma from mantle wells up to fill gap between separating plates.

  11. Divergent Plate Boundaries • Cooling and solidification of magma on earth’s surface • Constructive margins formed, where new sea floor (ocean crust )is generated. • New sea floor appears as series of ridges • Sea floor spreading occurs • As plate pulls apart again and new cracks appear, more magma rises to fill gaps creating more sea floor

  12. Divergent Plate Boundaries • Rocks found further away from ridge proves that new sea floor is created continuously • Example of divergent plate boundary : Mid-Atlantic Ridge, East African Rift Valley OLDER ROCKS YOUNGER ROCKS OLDER ROCKS RIDGES MAGMA http://whs.moodledo.co.uk/file.php/1365/EarthSystems/Earth%20Systems/Rift%20Valleys%20to%20Oceans.swf

  13. Convergent Plate Boundaries • Zones of Compression • Convection currents converge (coming together), the plates come together • Three types of convergent boundaries • Oceanic and Continental plate collide • Oceanic and Oceanic plates converge • Continental and Continental plates collide

  14. Oceanic-Continental • Known as destructive margins • Continental plate which is less dense will ride over oceanic plate • Oceanic plate Subducts (forced downwards the mantle), forming a deep elongated trough (ocean trench) • Volcanoes form in subduction zone • As oceanic plates sink deeper, it gradually melts and becomes magma http://www.classzone.com/books/earth_science/terc/content/visualizations/es0804/es0804page01.cfm?chapter_no=visualization

  15. Oceanic-Continental http://www.classzone.com/books/earth_science/terc/content/visualizations/es0804/es0804page01.cfm?chapter_no=visualization

  16. Oceanic-OCEANIC • Less dense oceanic plate ride over more dense oceanic plate • More dense oceanic plate subducts, formation of ocean trench • Magma is force through overriding oceanic plate, forming a chain of volcanic islands • Example: line of islands running from the Aleutians, Japan and down through Philippines

  17. Oceanic-OCEANIC

  18. Continental-Continental • Collision results in massive land form • No Subduction • Fold Mountain Range tend to form • Example: the Himalayan Fold Mountain Range

  19. Continental-Continental

  20. Transform fault boundaries • Also known as conservative margins • Two plates slide past each other • Fault-line created Continental Plate Continental Plate or Oceanic Plate Fault-line

  21. Transform fault boundaries • Example of a transform fault boundary is the San Andreas Fault http://www.classzone.com/books/earth_science/terc/content/visualizations/es0804/es0804page01.cfm?chapter_no=visualization

  22. Results of Plate Movements • Folding and Faulting • Earthquakes • Volcanoes

  23. Folding • When 2 plates collide, the rock strata (layers) will bend and warp as they are compressed • Features of folding: Synclines (downfold) and anticlines (upfold) ANTICLINE SYNCLINE

  24. Folding • Place where rock strata band over is called hinge line • The rock strata on either sides of the hinge is called limbs HINGE LINE LIMBS LIMBS

  25. Folding • Types of fold : • Symmetrical fold – both limbs of equal gradient • Assymmetrical fold- one limb steeper than the other • Recumbent fold- Limbs are nearly parallel • Overthrust old- One limb pushed forward so forcefully that the rocks may fracture, and it overrides the other limb. When the overriding limb becomes detached from the main fold, it is called a nappe

  26. Folding RECUMBENT SYMMETRICAL NAPPE ASYMMETRICAL

  27. Folding • Large scale folding will lead to formation of Fold Mountains • Examples of fold mountains: • The Himalayas • The Andes • The Zagros of Iran http://www.classzone.com/books/earth_science/terc/content/visualizations/es1105/es1105page01.cfm?chapter_no=visualization

  28. Faulting • Displaces rocks along a crack or fault line • Occurs in 3 ways: • Normal fault • Reverse fault • Tear fault • Can give rise to block mountains and rift valleys

  29. Normal fault • When rock strata are under tension caused by forces acting in opposite directions • Tension causes the rock strata to stretch and crack, developing a normal fault • One block of land then moves down (downthrown block) to form an escarpment • Example: The Tenton Mountain in Wyoming USA

  30. NORMAL FAULTS

  31. Reverse fault • When rock strata are compressed • Forces pushing towards each other causes the rock strata to fold, giving rise to reverse fault • One block of land moves up (upthrown block) against the direction of the fault, creating an overhanging scarp • The overhanging scarp collapses due to gravity, weathering and erosion, and produce a gentler slope • Example: Sierra Nevada Mountains of California

  32. RESULT FAULTS

  33. Tear fault • Also known as wrench fault or strike-slip fault • When plates slip past each other horizontally • Tensional or compressional forces act on the rock strata giving rise to tear faults • Big tear faults are known as transcurrent faults • Example: San Andreas Fault in the United States

  34. TEAR FAULT

  35. Block Mountains • Block raised between 2 parallel fault lines is called a block mountain • If surface is horizontal, it is termed as a horst • if block is tilted, it is termed tilt block • Examples of faulted blocks: • Hawkes bay in New Zealand

  36. HORST

  37. Rift valleys • Also known as agraben • Formation can be due to: • land between two parallel lines sink • land on either side of the two parallel lines are unpthrown above the central block of land • two plates pull apart • Example: • The East African Rift Valley • The Red Sea

  38. GRABEN http://www.iris.washington.edu/gifs/animations/faults.htm http://www.classzone.com/books/earth_science/terc/content/visualizations/es1103/es1103page01.cfm?chapter_no=visualization

  39. Earthquakes • Vibrations in earth’s crust caused by sudden release of energy • Energy released in the form of seismic waves and that radiate out from the epicentre • Point below the epicentre is called the point of origin where the earthquake originated from http://www.pbs.org/wnet/savageearth/animations/earthquakes/index.html

  40. Earthquakes • Two types of seismic waves: • P- waves (Compression waves) • alternately compress and release rocks in the direction the waves are moving • S- waves (Shear waves) • move rocks perpendicularly to the direction the waves are moving

  41. Earthquakes http://www.classzone.com/books/earth_science/terc/content/visualizations/es1002/es1002page01.cfm?chapter_no=visualization

  42. Earthquakes • Major earthquake zones: • Pacific Ring of Fire -Along the edge of the Pacific Ocean • Trans-Eurasian Belt –Where the Indo-Australian Plate and African Plate meet the Eurasian Plate

  43. Earthquakes http://www.classzone.com/books/earth_science/terc/content/visualizations/es1005/es1005page01.cfm?chapter_no=visualization http://www.classicalarchives.com/eq/

  44. EFFECTS OF Earthquakes • Displacement of earth’s crust • When earthquakes occur in the ocean floor: Tsunamis (huge tidal waves) • Devastation of cities and loss of lives

  45. MOUNT DOOM Lord of the rings

  46. VOLCANOES

  47. volcanoes • Found along plate boundaries or hotspots • Can be found on land or under water • Volcanoes on land : often form flat cones and the expulsions build up over the years. • Volcanoes under water: often form rather steep pillars and in due time break the ocean surface in new islands.

  48. volcanoes • Vulcanicity: when magma is forced towards earth’s surface from within the earth • Hotspot volcanoes: where the location has vulcanism for a long period of time • Example of hotspot volcano: Java Island in Indonesia http://www.classzone.com/books/earth_science/terc/content/visualizations/es0904/es0904page01.cfm?chapter_no=visualization

  49. volcanoes • Most volcanoes on the land are formed at destructive plate margins: • Oceanic crust melt, reduced density force the newly formed magma to rise. • As magma rises it rises up through weak areas in the continental crust, eventually erupting as one or more volcanoes.

  50. volcanoes • For example, Mount St. Helens is found inland from the margin between the oceanic Juan de Fuca Plate and the continental North American Plate.

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