Plate Tectonics
How can continents move? l In the 1960’s, scientists aboard the research ship Glomar Challenger drilled into the seafloor of the Atlantic Ocean and removed crust samples. l None of the rock samples were over 200 million years old. (Samples of continents are over 3 billion years old) l Rocks at the mid-ocean ridges were younger; rocks became older in both directions closer to the continents.
Glomar Challenger
l After analyzing the rock samples, scientists came up with a theory that molten material from Earth’s mantle is forced upward to the surface at mid- ocean ridges and cools to form new sea floor. l Movement in Earth’s mantle forces sections of crust apart, allowing magma to flow onto Earth’s surface and form new crust. l Therefore, the Atlantic Ocean is wider today than it was when Christopher Columbus crossed it!!!
Plate Tectonics- theory that Earth’s crust and upper mantle (lithoshphere) are broken into sections called plates that move on top of the asthenosphere.
Types of Plate Boundaries Convergent-plates collide Divergent-plates separate Transform-plates slide past each other
Plate Map
Converging Plates
Divergent Plates
Transform Plates
Convection Currents l Scientists believe plate movement is caused by convection currents. l When material in the mantle reaches an extreme high temperature, it rises. When it cools, it begins to sink back down. This motion creates a current, like when soup boils.
Convection currents
Convergent Boundaries Oceanic/Continental l Andes Mts (S. America) South American & Nazca Plates l Cascade Mts, Mt.St. Helens (N. America) North American & Juan de Fuca Plates
Effects of oceanic/continental convergence l Volcanic mountain chains l Faults l Earthquakes l Click picture for short video
Ocean/Continent Convergence
Andes Mountains
Mount St. Helens
Convergent Boundaries Con’t Oceanic/Oceanic l Japan Island chain Eurasian & Pacific Plates l Philippine Islands Eurasian & Pacific Plates
Effects of oceanic/oceanic convergence l Volcanic island arc l Faults l Earthquakes l Tsunamis
Ocean/Ocean Convergence
Mt. Pinatubo, Philiippines
Mt. Fugi, Japan
Convergent Plates Continued Continental/Continental l Appalachian & Atlas Mts. African & N. American Plates l Himalayas Indian & Eurasian Plates
Effects of continental/continental convergence l Folded mountain ranges l Faults l Earthquakes l Click pic for short video
Continent/continent convergence
Himalayas
Divergent Plate Boundaries Oceanic Crust l Mid Atlantic Ridge (MAR) and Iceland N. American & Eurasian plates Effects: l Mid ocean ridges l Faults l Earthquakes l volcanos
Computer generation of MAR
Mid Atlantic Ridge
Iceland
Continental crust divergence l East Africa, Red Sea & Rift Valley l Effects: l Rift valleys l Faults l Earthquakes l Inland seas l Rare volcanos
Red Sea
Transform Plate Boundaries Continental & Oceanic Plates San Andreas Fault (California) Pacific & N. American Plates Effects: l Faults l Volcanos Click for short video
Transform Boundary
San Andreas Lake
San Andreas trench
Hot Spots l Areas of volcanic activity formed by areas of intense heat in the mantle at places other than plate boundaries Ex: Hawaiian Islands, Yellowstone Natl. Park Click for short video
Hawaiian Islands
Cross section of hot spot