Unveiling the Mysteries of Plate Tectonics

1. Ch 10 Plate Tectonics A Moonenland Production A subsidiary of Moonco. Inc

4. Continental Drift • Alfred Wegener (1912) • German Meteorologist • Continents moved slowly to their current locations. • Pangaea- the single landmass of Earth that broke apart about 200mya . “All Land”

6. Evidence • Puzzle-like Fit • Coastlines of continents fit together like puzzle pieces. • Examples: S.America & Africa

7. Fossil Clues • Certain fossils of ancient animals & plantsare found on distant landmasses. • Freshwater/land-dwelling reptile Mesosaurus fossils have been found on South America & Africa.

8. Fossils of the ancient plant Glossopteris were found in Africa, South America, Australia, India, & Antarctica.

9. Climate Clues -Fossils of warm climate plants were found in present-day cold climates. (Coal) -Rocks deposited by glaciers from the ice ages have been found in present-day warm climates.

11. Rock Clues • Similar rock structures are found on different continents separated by oceans. -Appalachian mountains of the USA are similar to mountains found in Greenland & western Europe -Rocks of South America match those in Africa

12. Main objection to Wegener’s hypothesis was its inability to provide a mechanism for the movement of the continents.

13. Seafloor Spreading • Hypothesis • Radio waves were used to map the ocean floor. • Mid-ocean Ridges- underwater mtn ranges

14. Less dense magma flows sideways dragging the seafloor along. • As the seafloor spread apart, magma flows up through cracks in at the ridge forming new rock.

15. Midocean Ridge Rift Valley

16. Evidence • Drilling • Ocean floor rock samples show that the age of the rock gets older the further the rock is from the mid-ocean ridge

17. Magnetism • Changes in the magnetic alignment of the Earth are found in alternating bands in the seafloor rock.

18. Theory of Plate Tectonics • Theory • Combined theory of Continental Drift & Seafloor Spreading. • Earth’s crust & upper mantle (lithosphere) are broken into plates and move around on a plastic-like layer of the mantle (asthenosphere.)

20. Seven major plates: Pacific (largest) N. American S. American African Eurasian Australian Antarctic

22. Plate Boundaries • Divergent Boundaries • Two plates spread apart. • Where seafloor spreading occurs. • New crust is formed. Ex: Mid-Atlantic Ridge

23. Convergent Boundaries • Two plates come together (collide) • Oceanic plate will sink under a continental plate (subduction) producing a deep trench. Ex: Andes & Cascades

25. Two oceanic plates will converge resulting in a volcanic island arc. Ex: Mariana Islands

26. Two continental plates will converge & crumple forming folded mountains. Ex: Himalayas, Appalachians, & Alps

27. Transform Fault Boundary • Two plates slide past each other. • Move at different rates. • Also known as strike-slip faults. Ex: San Andreas Fault

28. Causes (Hypothesis) • Convection Currents • Hot magma rises in the mantle. • Magma hits the crust & cools. • Cooling magma sinks dragging the lithospheric plate with it (centimeters.) • Magma sinks into the mantle & reheats.

30. Features Formed by Tectonics • Faults • Cracks in the tectonic plates caused by stress. • Plate boundaries are also faults. • Movement along faults cause earthquakes.

32. Volcanoes • Magma produced by friction during subduction oozes up through the crust, erupts, & forms volcanoes.

33. Mountains • Convergent & Divergent boundaries form mountains. • Process of mountain building is called orogenesis. • -Volcanic Mountains

34. Folded Mountains • Horizontal rock layers are squeezed from opposite sides, causing them to buckle & fold. EX: Himalayans & Appalachians

35. Fault-block Mountains: Huge, tilted blocks of rock that are separated by faults. EX: Sierra Nevada

36. Upwarped Mountains- blocks of Earth’s crust are pushed up by forces inside the Earth. (Domes) EX: Rocky Mountains