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Plate Tectonics: What changes the positions of the continents over time?
DIVERGENT BOUNDARIES
Learning goals:
• WHAT CHANGES THE POSITION OF THE PLATES OVER TIME?
• Plates pulling apart– The ground cracks open making earthquakes and
hot molten rock to rise and fill the crack as it cools– All of the worlds oceans were made this way in a
process called sea floor/ ocean floor spreading– Spreading is currently happening at mid-ocean
ridges and on continents at rift valleys
• Tectonic Plate
• Plate Boundary
• Tectonic/Lithospheric/ plate – broken parts of all the crust and upper mantle
• Plate Boundary – an area where the broken lithospheric plates meet
Main ideaReview terms Supporting detail
Plate boundaries
• Plates move apart at Divergent boundaries
• DIVERGENT BOUNDARY• Also called:
– spreading boundary, – extension boundary,– separating boundaries, – creation boundaries
• Plates are pushed apart
• New crust/land is created – basalt an extrusive igneous rock is formed
Main Idea Supporting details
• Divergent Plates are under force
• Tension = force pulling away
– By convection currents in the asthenosphere
– Convection currents rise & separate pulling plates apart
Main IdeaSupporting details
• Two (2) types of Divergent plate boundaries
• Continent to Continent Divergent Boundaries
• Ocean to Ocean Divergent Boundaries
• Continent to Continent Divergent Boundaries
• Plates are pushed apart
• Process is called Rifting – (occurs on land)
• Rifting occurs on land and within a continent.
• Land form created is a Rift Valley• Continued rifting will eventually lead
to the Continent separating and the formation of an ocean
Mail Idea Supporting details
Continent
Convection currents
• 1. Rift-valleys form on land
• 2. Volcanoes form on land during the rifting process and are found in rift valleys
• Land forms/ land features/ Structures created at Continent to Continent Divergent boundaries
Mail Idea Supporting detail
• Processes that creates new crust
• SEA FLOOR SPREADING• Plates are pushed apart
• Process is called Seafloor Spreading occurs at the bottom of an ocean floor along the Mid-Ocean ridge
http://www.learner.org/interactives/dynamicearth/slip3.html
Mail IdeaSupporting detail
Water
Ocean plateOcean plate
Convection currents
Mid Ocean Ridge or Rises– can form and are located on ocean floors•The Mid Ocean Ridge is the Longest mountain range on Earth and it is almost all under water
Volcanoes–Can form underwater and are part of the Mid-ocean ridge
Main ideaSupporting detail
Land forms/land features/ Structures created at Ocean to Ocean Divergent boundaries underwater
water
Animation of rifting /seafloor spreading
Plate tectonics on a cocoa earth - Safeshare.TV
Mid ocean ridgeContinent
This is the process that separatedthe continents that created theAtlantic OceanImage of bathymetry/topography from NOAA
http://www.bioygeo.info/Animaciones/DivergentBoundary
Mid ocean ridges through out the world
The Mid-Atlantic Ridge – Safeshare.TV
Image by VIZZ
Mid- Ocean Ridge in Atlantic Ocean
Iceland – Mid ocean ridge rises above the sea
Volcanoes of Iceland
Fissure eruptions in Iceland
Volcano Eruption of Eyjafjallajökull, Iceland - Safeshare.TV
Great African Rift Valley
Great African Rift Valley
http://www.safeshare.tv/w/wGiTJskwRVJourney to the Galapagos Rift
Image courtesy of NOHA
Learning goals: Review
• WHAT CHANGES THE POSITION OF THE PLATES OVER TIME?
• Plates pulling apart– The ground cracks open making earthquakes and
hot molten rock to rise and fill the crack as it cools– All of the worlds oceans were made this way in a
process called sea floor/ ocean floor spreading– Spreading is currently happening at mid-ocean
ridges and on continents at rift valleys