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