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 idea Review 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 Idea Supporting 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 IdeaSupporting 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 IdeaSupporting 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 Mail Idea Supporting detail Water Ocean 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 idea Supporting 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 separated the continents that created the Atlantic Ocean Image of bathymetry/topography from NOAA

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

Journey 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