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Plate Tectonics. Ocean Topography. Ocean Ridges- underwater mountains; longest mountain range on Earth Trenches - Narrow depression in the seafloor How do they form?. Seafloor Spreading. Seafloor spreading : when new ocean crust is formed Formation of new crust
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Ocean Topography • Ocean Ridges- underwater mountains; longest mountain range on Earth • Trenches- Narrow depression in the seafloor • How do they form?
Seafloor Spreading • Seafloor spreading: when new ocean crust is formed • Formation of new crust • magma is forced towards the surface • As the ridge separates the magma fills the gap created • This will continue to happen an new ocean crust will continue to generate
Plate Tectonics • Tectonic plates are huge pieces of crust that cover the Earth • Move through convection currents
Divergent Boundaries • Divergent Boundaries- two tectonic plates move apart • Occur in Ocean ridges • Seafloor spreading
Convergent Boundaries • Convergent Boundaries: 2 tectonic plates move towards one another • When 2 plates collide the denser plate descends below the other plate • This process is called subduction
Convergent Boundaries • Oceanic-Oceanic: • forms an ocean trench • Oceanic-Continental: • Oceanic plate is more dense and it is subducted. Produces trenches and volcanic arc • Continental-Continental • The crust are unable to subduct due to rocks so the continents collide and form massive mountain regions.
Transform Boundaries • Transform Boundaries • Plates slide horizontally • Responsible for most earthquakes • Ex. San Andreas Fault