The Story of the Discovery of Plate Tectonics In 1915 a German scientist named Alfred Wegener proposed hypothesis called CONTINENTAL DRIFT The same fossils were found on different continents The same mountains were found on different continents Scratches from ice were found in deserts in India and Africa All Continents had been joined together in a supercontinent, Pangaea and has since drifted apart Circle is where mountains split, half are found in East US, the other half in Europe This plant fossil Glossopteris was found on 5 different continents Scratches left by ice show that India and africa were much farther South on Globe WEGENER’S HYPOTHESIS WAS REJECTED BECAUSE HE COULDN”T PROVE WHY CONTINENTS MOVED! During World War II scientists began to use sonar to map the ocean floor With Sonar Scientists Discovered: Mid-Ocean Ridges Or Underwater volcanic mountain ranges Mid-Ocean Ridges Or Underwater volcanic mountain ranges Deep Ocean Trenches Or Deep holes where plates slide under eachother Deep Ocean Trenches Or Deep holes where plates slide under eachother *2 Basalt rock was found at the mid-ocean ridge, it comes from Volcanoes and makes the ocean floor of every ocean * 3 Ocean floor was found to be sinking below continents or other crust at the trenches… this process was named subduction *1 Youngest Rock was Found at the ridge and oldest the farthest away from the ridge Other Observations In 1963 Harry Hess created the idea of Sea-Floor Spreading New ocean floor forms at the mid-ocean ridges, slowly spreads out to form new ocean basins before sinking below lighter plates

WarmUp ( ) What is going to happen to all of our continents within the next 250 million years? – They will collide to form another supercontinent

WarmUp ( ) Who developed the concept of Continental Drift and what was his evidence to support it? – Alfred Wegener: same fossils on different continents, and same rocks from mountains, and how continents fit together like a puzzle

WarmUp ( ) Describe the process of sea-floor spreading. Agenda: 1.WarmUp 2.How It’s Made 3.Finish Poster 4.Watch Video Agenda: 1.WarmUp 2.How It’s Made 3.Finish Poster 4.Watch Video

WarmUp ( ) Name the three different types of plate boundaries. – Convergent boundary (plates collide with each other) – Divergent boundary (plates move away from each other) – Transform boundary (plates slide past each other) Agenda: 1.WarmUp 2.How It’s Made 3.Plate Tectonic Activity Agenda: 1.WarmUp 2.How It’s Made 3.Plate Tectonic Activity