Presentation on theme: "Theory that all of the continents were once one large landmass (Pangaea) that has broken up and drifted apart. –Alfred Wegener Evidence –Continents fit."— Presentation transcript:
Theory that all of the continents were once one large landmass (Pangaea) that has broken up and drifted apart. –Alfred Wegener Evidence –Continents fit like pieces of a puzzle –Fossils of same species animal & plants found on separate continents Glossopteris –Rock formations Matching mountain chains –Climatic conditions Coal fields in Antarctica
Pangaea –Greek for “ all Earth” Pangaea broke into two huge continents –Laurasia –Gondwana These two split again to form the current continents
Mid-ocean Ridges –Underwater mountain chain that runs through the Earth’s oceans. Sea-floor spreading –Process in which new lithosphere forms Magma rises to the surface through the mid-ocean ridge forming new oceanic crust Tectonic plates spread apart and magma fills the gap. As new crust forms older crust moves away from the M.O.R.
Crust closer to the mid-ocean ridges is younger than crust further away. Subduction –Process in which old ocean floor goes back into the mantle through trenches
Earth’s north and south poles have changed places many times Molten rock contains contains tiny grains of magnetic minerals These minerals align with the magnetic field of the Earth. As the magnetic field reverses and the ocean and new ocean floor is formed it leaves a record of this change.