plate tectonics...the theory of continental drift is now based on seafloor spreading. there seems to...
TRANSCRIPT
PLATE TECTONICS
• Continental drift : PANGAEA ; Gondwanaland and Laurasia
• EVIDENCE
• Plate boundaries
• Plate movements• Destructive margin
• Constructive margin
• Collision margin
• Conservative margin
The Theory of Continental Drift
• A theory put forward by Alfred Wegener in 1912.
• The continents were once joined together in a single landmass.
• It split up to form separate continents.
Pangaea
Original Continent : Pangaea
Tectonic Plates and Continental Drift
Pangea
Proof that Pangaea existed
Movement of the continents .
• Heat inside the earth is the driving force .
• Heat rises from the mantle.
• It deforms the earth’s crust and breaks it into large pieces .
• Tectonic plates carry both continents and oceans.
Convection Currents .
• Heat in the mantle causes convection currents which cause the plates to move.
• The plates move a few centimetres every year.
• The edges of the plates are called plate boundaries.
• The mantle has a plastic consistency and can therefore move or flow. ( slush )
• Associated with earthquakes and volcanoes.
Plate boundaries• Constructive/ diverging plate boundaries
• New seafloor is being formed and plate move apart• Mid oceanic ridges – seafloor moving apart
• Rift valleys – continental plate move apart
• Destructive/ converging plate boundaries• Seafloor pushed back into mantle
• trenches – seafloor collides
• Peripheral fold mountains – seafloor and continent collides
• Inter-cratonic fold mountains – 2 continents collide
• Transform boundary• Plate boundaries that move parallel to each other in
opposite directions
Seafloor spread lead to plate tectonics
Constructive plate boundary
Destructive plate boundary
The theory of continental drift is now based on seafloor spreading. There seems to be hotspots in the mantle that cause convection currents that drags the solid crustal plates along. Plate tectonics refer to the study of landforms formed due to these movements.
Destructive
plate
boundaries:
Trenches
Peripheral
fold
mountains
Intercratonic
fold
mountains
Activity 7: Identify Plate types and movementsPlate Margin Two types of crust involved Direction of plate
movement
Conservative Continental Crust Slide sideways past each other. Eg: San Andreas Fault
Destructive Oceanic and Continental crust
Move towards each other. Eg: Nazca and South American Plate
Collision Two Continental crusts Towards each other. Eg: Indo-Australian and Eurasian plate
Constructive Oceanic and Continental crust
Moves away from each other, Eg: Mid-Atlantic ridge