Sea Floor Spreading Mr. R & Ms. GEarth Science Discovery: - -WWII sonar mapping and military advancements to combat enemy hiding locations in the Atlantic Ocean. - -Harry Hess (1963) Princeton Professor US Navy recruit inn WWII tracked and recorded the sonar machine to map the ocean floor and discover the Mid-Atlantic ridge. Sea Floor Spreading Mr. R & Ms. GEarth Science Convective Upwelling: - -Areas on the seafloor that are openings for convective upwelling from the aesthenosphere. - -Ridges/rises are features that are found at these locations - - Ridges represent where the divide in the crust occurs and rock age records confirm the younger rocks are closer to the ridge and get progressively older the further away it gets. Revolutionary theory: - -Seafloor spreading is a large piece of evidence to confirm continental drift theory. - -Seafloor mapping illustrated the on the ocean basins openings for convective upwelling from the aesthenosphere are present. - -Ridges/rises are features that are found at these convective upwelling locations. - -Ocean trenches are deep parts of the ocean which are usually located near continents. These features are a component of seafloor spreading and connect the ocean movement to plate tectonics. Sea Floor Spreading Mr. R & Ms. GEarth Science Currently the most up-to-date map of the worlds oceans (5-15% is mapped) Sea Floor Spreading Mr. R & Ms. GEarth Science Understanding the Age of the Seafloor Sea Floor Spreading Mr. R & Ms. GEarth Science Rocks contain magnetic elements and when they cool and form, they become aligned with the current magnetic polarity of the Earth. - Magnetic north and south pole over time have reversed (cyclic) 1 million 200,000 year intervals. North pole is located over Antarctica. - -Geographic north and south do not change (reverse) Paleogeomagnetic Reversals Sea Floor Spreading Mr. R & Ms. GEarth Science Paleogeomagnetic Reversals Sea Floor Spreading Magnetic Stripes Mr. R & Ms. GEarth Science Sea Floor Spreading Magnetic Stripes Mr. R & Ms. GEarth Science Using magnetic dating of the rocks, the Atlantic is a perfect example of a seafloor spreading - -Magnetic north and south pole over time have reversed (cyclic) 1 million 200,000 year intervals. North pole is located over Antarctica. - -Geographic north and south do not change (reverse) Convection Currents Hot magma in the Earth moves toward the surface, cools, then sinks again. Rule hot things rise, cold things sink Creates convection currents beneath the plates that cause the movement. https://www.youtube.com/watch?v=ryrXAGY1dmE