Development of the Theory of PLATE TECTONICS

Continental Drift 1912 – Alfred Wegener (German) suggested that the continents were once joined together forming a super- continent called Pangaea. Pangaea – all land Panthalassa – all ocean Laurasia – Northern section of Pangaea Gondwanaland – Southern section of Pangaea

Evidence for Continental Drift By 1912 the maps of the continents were accurate enough to use scientifically… 1) THE COASTLINES OF CONTINENTS FIT LIKE A PUZZLE!

Evidence for Continental Drift Fossil evidence 2) MESOSAURUS (ancient alligator) – fossils found in South America and Africa 3) GLOSSOPTERIS (ancient fern tree) – fossils found in Antarctica, India, Australia, Africa, and South America

Other Fossils ) Lystrosaurus- Land reptile found in south Africa, Antarctica, and India. Cynognathus- Land mammal-like reptile found in central South America and Africa.

Evidence for Continental Drift Rock Types 4) The Appalachian Mountains have the same composition and age as the mountains found in Africa and Northern Europe

Evidence for Continental Drift Climate Change 5) Glacial erosion (striations and erratics) are found in tropical and sub- tropical locations in Africa, South America, India, and Australia

EVERYONE LAUGHED AT HIM!!! ALFRED WEGENER COULD NOT EXPLAIN HOW OR WHY THE CONTINENTS MOVED. IT JUST SEEMED TOO IMPOSSIBLE FOR PEOPLE TO BELIEVE.

Sea-Floor Spreading 1960s – Harry Hess (American), Glomar Challenger Used modern day SONAR to map the ocean floor. He discovered the Mid-Ocean Ridges AND suggested that the sea-floor is actually growing

Evidence for Sea-Floor Spreading 6) Age of Rocks on Sea-Floor Hess found that the rocks were youngest near the mid-ocean ridge and oldest near coastlines of continents.

Evidence For Sea-Floor Spreading 7) Paleomagnetism The magnetic poles of Earth have shifted several times throughout the course of Earth’s History. When a rock forms it takes on the magnetic orientation of the Earth at that time The magnetic orientation is mirrored on the ocean floor

The Final Piece of Evidence Earthquake Data proves that pieces of the earth’s crust (plates) MOVE!!!!!!! Do Now: see handout

Complete the Plate Map Activity

1.Put your name and a title on front of puzzle. Plate Tectonic Puzzle -Using your notes, http://www.learner.org/interactives/dynamicearth/plate.html, and pgs. 256-257 of your textbook, complete the following. 1.Put your name and a title on front of puzzle. 2. Complete a key to indicate the 3 ways plates interact. -Divergent -Convergent -Transform 3. Like the examples show, identify all plates by name. 4. Label the location of all 8 of the following, -Himalayan Mtns -Appalachian Mtns -Mid-Atlantic Ridge -African Rift Valley -Andes Mtns -San Andreas Fault -Japan -Mariana Trench 5. Using the colors from your key, identify which type of plate interaction exists at each boundary for the items from #5.

PLATE TECTONICS The theory of Plate Tectonics suggests that the crust and upper mantle (lithosphere) is broken into sections called plates. The plates move and float on the liquidy part of the mantle called the Aesthenosphere.

PLATE TECTONICS The plates grow, shrink, and move due to CONVECTION CURRENTS IN THE MANTLE

How do the plates interact? 3 types of plate boundaries: Convergent Boundary – move toward one another Divergent Boundary – move away from one another Transform Fault Boundary – slide past one another

Convergent Boundaries (type 1) Oceanic Crust – Continental Crust Subduction Occurring – creates trenches, coastal mountains and volcanoes Examples: Andes Mountains, Appalachian Mountains

Convergent Boundaries (type 2) Continental Crust – Continental Crust Creates large mountain ranges Examples: Himalaya Mountains

Convergent Boundaries (type 3) Oceanic Crust – Oceanic Crust Subduction Occurring – creates trenches, island arcs and volcanoes Examples: Japan Island Arc, Mariana Trench

Divergent Boundaries (type 1) Mid-ocean ridges (Mid-Atlantic Ridge)

Divergent Boundaries (type 2) Rift Valleys (African Rift Valley)

Transform Fault Boundaries Creates Earthquakes (San Andreas Fault)

Practice