Continental Drift and Plate Tectonics

1. Continental Drift and Plate Tectonics

2. http://pubs.usgs.gov/gip/dynamic/historical.html

3. 1912 - Continental Drift -- introduced by a 32-year-old German meteorologist named Alfred Wegener.

4. Continental Drift • Wegener’s hypothesis that all the continents had once been joined in a single landmass and have since drifted apart.

5. Wegner based his theory on: • the puzzle fit of the coasts of the continents 2. the matching geologic features between continents now separated 3. the identical fossil plants and animals found on separate continents

9. Past location of Antarctica http://maps.unomaha.edu/Maher/plate/week10/USGSDynamicEarthfossils.gif

10. www.mnh.si.edu/.../4_1_2_3_glossopteris.jpg The picture above is of Antarctica as it looks today – below is a picture of a tree as it would have looked and the fossils from this kind of tree – found in the frozen ground of Antarctica.

11. The discovery of fossils of tropical plants in Antarctica led to the conclusion that the frozen land previously must have been situated closer to the equator, in a more temperate climate where lush, swampy vegetation could grow.

13. Heat and Earth’s Interior

14. Temperature • Measure of the average kinetic energy of the individual particles in an object. The particles of hot cocoa move faster than those of chocolate milk. Which drink has particles with the greater average kinetic energy? Hot cocoa

15. Heat • Movement of thermal energy from a substance at a higher temperature to another at a lower temperature. • Heat is thermal energy moving from a warmer object to a cooler object.

16. How Is Heat Transferred? • Heat is transferred by conduction, convection, and radiation.

17. Conduction • Heat is transferred from one particle of matter to another without the movement of matter itself. • Example: • Think of a metal spoon in a pot on the stove. Fast particles of hot electric coil collide with slow particles of cool pot. Particles of pot collide with particles of water, which collide with particles of spoon. As the particles move faster, the metal spoon becomes hotter.

18. Convection • Heat is transferred by the movement of currents within a fluid (a liquid or gas). • Example: • When water at the bottom of a pot is heated, particles move faster, and farther apart. Heated water is less dense so it rises to the top of the pot. The surrounding cooler water flows into the bottom of the pot in a circular motion called a convection current.

19. Radiation • Transfer of energy by electromagnetic waves. • Radiation does not require matter to transfer thermal energy. • Example: • You can feel radiation from a bonfire or heat lamp from a distance.

20. To understand plate tectonics, we need to review the structure of the Earth.

21. Crust Continental Crust: 25 miles thick AND LESS DENSE Ocean Crust: 4 miles thick AND MORE DENSE http://www.spring.net/geo/JohnVolos/Public/Portal/EARTH_MECHAN/3.gif

22. The solid part of the Earth is the lithosphere. It has two parts – the crust and part of the upper mantle. • http://www.deafhoosiers.com/sci/soarhigh/lithosphere/lithosphereComp.html

23. Mantle • Uppermantle – solid • Belowthelithosphereistheasthenospherewherethe material issoft and can flow.

24. Below the lithosphere is the asthenosphere – where convection currents cause the plate movements. • http://www.physicalgeography.net/fundamentals/images/tectconvection.gif

25. OuterCore • Made of molten metal thatsurroundstheinnercore. • Behaveslike a thickliquid. • Onlylayerthatisentirelyliquid.

26. InnerCore • Dense ball of solid metal. • Extreme pressuresqueezesatoms of iron and nickel so muchthattheycannot spread out and becomeliquid

27. Convection current movement is the result of the transfer of heat from the interior of the Earth. As the material is heated, it expands and rises.

28. Convection Currents in the Mantle 1. Material in the asthenosphere portion of the mantle is heated. 2. Hot columns of mantle material rise slowly through the asthenosphere. 3. The hot material spreads out an pushes the cooler material out of the way. 4. The cooler material sinks back into the asthenosphere.

29. Convection Currents

31. Platetectonics • Thetheorythatpieces of theEarth’slithosphere are in constantmotion, drivenbyconvectioncurrents in themantle.

32. The current location of the 7 major plates.

33. The regions where plates meet are called plate boundaries – these regions are active with different types of geological occurrences – depending on the type of boundary.

34. crashing: Convergent Boundaries, • pulling apart: Divergent Boundaries, • or sideswiping: Transform Boundaries

35. Diagram of the earth's major tectonic plates, showing locations of volcanoes.

36. http://www.platetectonics.com/book/page_2.asp

37. http://www.ngdir.ir/sitelinks/kids/Image/geology-farsi/Map.gifhttp://www.ngdir.ir/sitelinks/kids/Image/geology-farsi/Map.gif

38. http://www.platetectonics.com/oceanfloors/index.asp

39. Where two plates spread apart, cracks or rifts form in the earth's crust. We see this force at work today in Iceland, where that island nation (and all of the middle of the Atlantic ocean) is spreading apart, and volcanoes are filling in the cracks with lava.

40. Plate separation is a slow process. For example, divergence along the Mid Atlantic ridge causes the Atlantic Ocean to widen at only about 2 centimeters per year.

41. The Atlantic ocean is spreading about 3/4ths of an inch per year. • In your lifetime, North American will move westward the length of a man's body.

42. When two plates move toward each other, the denser one is forced under the other in a process called subduction.

43. Deep trenches are formed when subduction happens in the ocean, also it gives rise to earthquake activity and volcanic islands. Japan is such a place, in the Pacific Ring of Fire.

44. Places where plates crash or crunch together are called convergent boundaries. Plates only move a few centimeters each year, so collisions are very slow and last millions of years

45. On land, continents colliding cause the land to raise up, (geologists call it uplifting) and this force can build mountain ranges. Right now, India is colliding with the Eurasian Plate, causing the Himalayan Mountains. The Andes mountains of South America are the result of the partial melting of the plate being subducted, with the resultant molten rock (magma) rising through the continental crust and building a distinctive mountain chain down the length of that continent.

46. Transform BoundariesPlaces where plates slide past each other are called transform boundaries. Although transform boundaries are not marked by spectacular surface features, their sliding motion causes lots of earthquakes

47. The Hawaian Islands sit on the Pacific Plate. As this plate moves, it appears that it is moving over a "hot spot" in the mantle.

48. The Hawaiian island chain was formed from volcanic eruptions, but only one volcano is active at a time – the one over the hot spot.

49. The large island, Hawaii, is the most recent volcanic activity. Notice how the islands in the chain get progressively older –the result of the moving plate.