4 LESSON_Q1

• Tectonic Plates


  Plates that make up the Earth's lithosphere and move at an average of 2 to 20 cm per year
• Finding out the explanation for the movements of tectonic plates took a lot of effort from scientists
• Different theories and concepts were put forward until the accepted scientific consensus evolved into the current theory of plate tectonics
• Learning Competency


  Describe the possible causes of plate movement
• Specific Learning Objectives


  • Enumerate the various theories, concepts and scientists that contributed to the current scientific explanation of why the tectonic plates move
  • Describe the concepts put forward by each theory or concept
  • Trace how the theories and concepts evolved into the theory of plate tectonics
  • Explain how plate tectonic theory explains the possible causes of plate movement
• Continental Drift Theory


  Continents were once connected as one landmass called Pangaea, which broke down into individual continental landmasses that moved through unmoving oceans/seafloor
• Seafloor Spreading Theory


  Hot magma rises up from the mantle and creates a crack in the Earth's crust which we call an ocean ridge. The magma pushes the two sides of the seafloor causing each to move sideward. This magma fills in the gap then solidifies and forms new seafloor.
• Convection Currents


  In the mantle, magma materials rise up as they are heated up and sink down as they cool. This forms magma currents that circulate from the deeper parts of the mantle up to the bottom boundary of the lithospheric plates and back down.
• Interior Structure of the Earth

  The Earth's layers are Crust, Mantle, Outer Core and Inner Core. The inner core is made up of nickel and iron, is the hottest and is solid because of the tremendous pressure exerted by the layers above. The outer core has the same composition but it is cooler and is in liquid state. The mantle contains a layer which is plastic-like and therefore flows like a fluid.
• Continental Drift Theory and Seafloor Spreading Theory


  They differ in their views on the oceans/seafloor
• Convection Currents and Seafloor Spreading Theory

  Convection currents support seafloor spreading theory by providing the important material (magma) mentioned in seafloor spreading theory
• Interior Structure of the Earth

  It implicitly explains the existence of convection currents by showing that the mantle contains a plastic-like layer that can flow like a fluid, and that the inner core is the hottest part of the Earth
• Iron


  The hottest and is solid because of the tremendous pressure exerted by the layers above
• Outer core


  Has the same composition but it is cooler and is in liquid state
• Mantle


  Contains a layer which is plastic-like and therefore flows like a fluid
• The continental drift theory is opposed by the seafloor spreading theory in terms of what they say about the oceans/seafloor
• Convection currents


  Support seafloor-spreading theory
• The interior structure of the Earth implicitly explains the existence of convection currents
• Temperature differences in the mantle and the layers below it drive the formation of convection currents
• The core serves as the source that heats up materials at the bottom of the mantle layer kickstarting the circular movement of molten rock and magma
• Factors for the motion of the lithospheric plates

  • Ridge push
  • Mantle drag
  • Slab pull
• The Theory of Plate Tectonics explains how the features of the earth such as mountains, volcanoes, trenches etc. are formed or built
• The continental drift theory provided no mechanism or means of how the continental masses moved
• The seafloor spreading theory addressed the weakness of the continental drift theory by offering an explanation to why the continents moved
• The seafloor spreading theory contradicts the continental drift theory in terms of the oceans/seafloor being the actual site of tectonic activity
• Convection currents in the mantle are what break the seafloor to form an ocean ridge and start the process of seafloor spreading
• The lithosphere floating on top of the asthenosphere is affected by any movement in the fluid
• The Earth has three compositional layers - crust, mantle and core
• The mantle is divided into three sublayers - the uppermost rigid part of the mantle, the asthenosphere and the mesosphere
• The core is subdivided into the liquid outer core and the solid inner core
• The crust and the first sublayer of the mantle (the uppermost rigid part of the mantle) form the outermost mechanical layer of the Earth - the lithosphere
• The asthenosphere has different mechanical properties compared to the lithosphere because it is partially melted and it flows like a fluid
• The earth's hard outermost mechanical layer, the lithosphere, is fragmented into several segments called lithospheric/tectonic plates
• These plates float on top of a fluid-like mechanical layer called the asthenosphere
• Materials in the mantle which includes the asthenosphere form convection currents
• Convection currents form when the materials at the bottom of the mantle are much hotter than the materials at the top of the mantle
• Lithosphere


  The Earth's hard outermost mechanical layer, fragmented into several segments called lithospheric/tectonic plates
• Asthenosphere


  A fluid-like mechanical layer that the lithospheric plates float on top of
• Convection currents in the mantle


  Hotter materials at the bottom of the mantle float up while colder materials sink down, forming a circular flow of magma
• Convection currents in the asthenosphere


  Drag the lithospheric plates floating above it, causing them to move