2.  Layers – by composition ◦ Crust ◦ Mantle ◦ Core - Granite/Basalt - Peridotite/Gabbro - Iron/ Nickel

3.  Layers – by physical properties ◦ Lithosphere ◦ Asthenosphere ◦ Outer Core ◦ Inner Core - Solid/ rigid - Platic-like / silly putty - Liquid - Solid

4.  Crust ◦ Continental crust  Average rock density about 2.7 g/cm3  Composition = Granitic igneous rock

5.  Crust ◦ Oceanic crust  Density about 3.0 g/cm3  Composition = Basaltic igneous rock

6.  Mantle ◦ Contains 82% of Earth’s volume ◦ Upper portion has the composition similar to peridotite ◦ Two parts  Asthenosphere -upper mantle  Mesosphere -lower mantle

7.  Core ◦ Larger than the planet Mars ◦ Mostly iron with some nickel  Average density is nearly 11 g/cm3 ◦ Two parts  Outer core - liquid  Inner core - solid due to excess pressure

8.  Core ◦ Responsible for Earth’s magnetic field  Made of material that conducts electricity  Core is mobile

9.  How do we know what is inside the Earth?? ??

10.  Seismic waves ◦ P waves ◦ S waves Travels through liquids as well as solids In all materials, P waves travel faster than do S waves Cannot travel through liquids

11.  Seismic waves ◦ Seismic waves refract (bend) as they pass from solid to plastic-like to liquid material. ◦ P & S wave shadow zones created by this.

15.  Researchers noted geographic fit of continents, e.g. Africa and S. America  Seuss, 1885, proposed super continent by studying fossils, rocks, mountains  Alfred Wegener - First proposed his continental drift hypothesis in 1915

16.  All land was joined together as one Supercontinent called Pangaea which began breaking apart about 200 million years ago moving.  Pangaea Activity link  http://www.saskschools.ca/curr_content/ rbtboxes/mcrust/objects/pangea.html http://www.saskschools.ca/curr_content/ rbtboxes/mcrust/objects/pangea.html Wegener’s Hypothesis:

17.  Fit of the continents

18.  Rock type & structural similarities

19.  Fit of the continents  Rock type & structural similarities  Fossil evidence Fossils of Mesosaurus have been found on both sides of the South Atlantic and nowhere else in the world. Fossil remains of this and other organisms on the continents of Africa and South America appear to link these landmasses during the late Paleozoic and early Mesozoic eras.

20.  Fit of the continents  Rock type & structural similarities  Fossil evidence  Past climate evidence

21. New Technology adds new evidence.

22.  Proposed by Harry Hess in the late 1950s / early 1960s New crust forms at ocean ridges Old crust destroyed at trenches Developed theory of sea floor spreading driven by convection cells

23.  Harry Hess’s Evidence: Ocean floor is NOT flat! US Navy used SONAR to measure ocean floor depth under Hess’s direction Found a Mountain Range in the middle of the Atlantic Called it the Mid-Atlantic-Ridge

24.  Age of Sea Floor A – D represent drilling sites on the ocean floor. Which samples had the youngest rock? Which the oldest? Oldest rock on sea floor only 200 m.y. (million years) Earth 4.6 b.y. B and C A and D

26.  Earth's magnetic field resembles that produced by a large bar magnet.  Seafloor mapping in the 1950’s and 1960’s showed Earth’s polarity switched many times in the past. ◦ Paleomagnetism = the study of past polarity of Earth

28. As new basalt is added to the ocean floor at the mid-ocean ridges, it is magnetized according to Earth's existing magnetic field. Hence, it behaves much like a tape recorder as it records each reversal of the planet's magnetic field.

29.  Hot spots ◦ Caused by rising plumes of mantle material ◦ Volcanoes can form over them (Hawaiian Island chain) ◦ Most mantle plumes are long-lived structures and at least some originate at great depth, perhaps at the mantle-core boundary

33. + Continental Drift + Sea-Floor Spreading + Paleomagnetism = Plate Tectonics

34. A New Theory

35.  Earth’s lithosphere is broken up into plates  Hot, weak asthenosphere allows for plates to move  Plates are in motion and continually changing in shape and size ◦ Move very slowly 2 – 5 cm/yr

36. Evidence of Plate Boundaries

39.  Plate boundaries ◦ All major interactions among individual plates occur along their boundaries ◦ These interactions cause consequences such as:  Earthquakes  Volcanic eruptions

40.  Plate boundaries ◦ 3 Types of plate boundaries 1.Divergent plate boundaries 2.Convergent plate boundaries 3.Transform fault boundaries

41.  Divergent Plate boundaries ◦ Most are located along the crests of oceanic ridges  Mid-Atlantic-Ridge (MAR) ◦ Also continental rifts  Great African Rift Valley ◦ A few are on land  Great African Rift Valley  Iceland

44. The East African rift – a divergent boundary on land

45. Formation of Ocean Basins Ex: Red Sea Ex: Great Rift Valley Ex: Atlantic Ocean Ex: Yellowstone National Park

46.  Convergent plate boundaries ◦ Where two plates collide ◦ 3 Types 1.Oceanic-Continental convergence 2.Oceanic-oceanic convergence 3.Continental-continental convergence

54.  Transform fault boundaries ◦ Plates slide past one another ◦ No new lithosphere is created or destroyed ◦ Transform faults  Most join two segments of a mid-ocean ridge as parts of prominent linear breaks in the oceanic crust known as fracture zones