1. Plate Tectonics The grand unifying theory of Geology Plate tectonics controles Distributions of geologic materials and resources (e.g., Minerals, Energy, Water…) Geologic Hazards (e.g., earthquakes, volcanoes, landslides, tsunamis…) Landscape features (e.g., mountain ranges, oceanic trenches, continents, rift valleys…)

2. Formation of Earth http://www.psi.edu/projects/planets/planets.html Birth of the Solar System Nebular Theory (pg. 24, Kehew) Rotating nebula contracts Begins to flatten and collapse into center to form the sun. Clusters of asteroids coalesced to form planetesimals and moons (planetary accretion) around 4.6 billion years ago (bya) (Meteorites are iron-rich or rocky fragments left over from planetary accretion)

3. www.psi.edu/projects/ planets/planets.html www.geol.umd.edu/~kaufman/ ppt/chapter4/sld002.htm Orion Nebula www.hubblesite.org

4. Formation of the Planets The mass of the center of the solar system began nuclear fusion to form the sun The inner planets were hotter and gas was driven away leaving the terrestrial planets (Fe, O, Si, Mg…) The outer planets were cooler and more massive so they collected and retained the gasses forming the “Gas Giants” Gas Giants Terrestrial Planets www.amnh.org/rose/backgrounds.html

5. Differentiation of the Planets The relatively uniform iron-rich proto planets began to separate into zones of different composition: 4.5 bya Heat from impacts, pressure and radioactive elements cause iron (and other heavier elements) to melt and sink to the center of the terrestrial planets (Kehew Fig. 2-4) Lab. Man., Fig. 1.7a: Zones of the earth’s interior

6. Continental Crust (Silicic) Further Differentiation of Earth Lighter elements such as Oxygen, Silicon, and Aluminum rose to form a thin, rigid crust The crust, which was originally thin and basaltic (iron rich silicate), further differentiated to form continental crust which is thicker, iron poor, silica rich and lighter Kehew Fig. 2.5 Mid-Ocean Ridge (New Crust) Oceanic Crust (Basalt) Deepest Mine Deepest Well

7. Composition of Earth and Crust Element (Atomic #) Chemical Symbol % of Earth % of Crust (by Weight) Change in Crust Due to Differentiation Oxygen (8)O3046.6 Increase  Silicon (14)Si1527.7 Increase  Aluminum (13)Al<18.1 Increase  Iron (26)Fe355.0 Decrease  Calcium (20)Ca<13.6 Increase  Sodium (11)Na<12.8 Increase  Potassium (19)K<12.6 Increase  Magnesium (12)Mg102.1 Decrease  All Others ~81.5

8. Crust and Mantle Lithosphere and Asthenosphere The uppermost mantle and crust are rigid, solid rock (Lithosphere) The rest of the mantle is soft and solid (Asthenosphere) The Continental Crust “floats” on the uppermost mantle The denser, thinner Oceanic Crust comprises the ocean basins

9. Rocks and Sediment Products of an Active Planet Earth’s structure leads to intense geologic activity Inner core: Solid iron Outer core: Liquid iron, convecting (magnetic field) Mantle (Asthenosphere) : Solid iron-magnesium silicate, plastic, convecting Crust (Lithosphere): Rigid, thin O, Si, Al, Fe, Ca, Na, K, Mg… Crust: Rigid, Thin Mantle: Plastic, Convecting 47%, 28, 8, 5, 4, 3, 3, 2

10. Pangea 225 million years ago 135 mya 65 mya Today

11. Evidence of Continental Drift Glacial striations match across oceans Kehew, Fig. 2.27

12. Evidence of Continental Drift Matching rock types and mountain ranges Kehew, Fig. 2.27

13. Evidence of Continental Drift Fossils of land plants and animals

14. Evidence of Continental Drift Magnetic Evidence Reversals in Earth’s magnetic field are recorded in newly formed rocks Kehew, Fig. 2.7

15. Evidence of Continental Drift Age of Earth’s Oceanic Crust Kehew, Fig. 2.32

16. The Lithosphere is broken into “plates” (7 maj., 6 or 7 min.) Plates that “ride around” on the flowing Asthenosphere Carrying the continents and causing continental drift See Kehew, Figure 1.19 Lithospheric Plates

17. Kehew, Fig 2.24

18. Three Types of Plate Boundaries Divergent  |  Convergent  |  Transform e.g., Pacific NW See Kehew, Fig. 2.38

19. Where plates move away from each other the iron-rich, silica-poor mantle partially melts and Divergent Plate Boundaries Asthenosphere Lithosphere Simplified Block Diagram Extrudes on to the ocean floor or continental crust Cool and solidify to form Basalt: Iron-Rich, Silica-Poor, Dense Dark, Fine-grained, Igneous Rock

20. New Oceanic Crust Forming at Mid-Ocean Ridge Oceanic Crust Lithospheric Plate Movement Magma Generation Characteristics of Divergent Plate Boundaries Divergent Plate Boundary Stress Earthquakes Volcanism Rocks Features Lithosphere Asthenosphere See Kehew, Fig. 2.29 Welling up of hot mantle rock (solid but soft) Fissure Eruptions Shallow Earthquakes Dark, Dense, Basalt

21. Characteristics of Divergent Plate Boundaries Oceanic Crust Magma Generation Divergent Plate Boundary Stress: Tensional  extensional strain Volcanism: non-explosive, fissure eruptions, basalt floods Earthquakes: Shallow, weak Rocks: Basalt Features: Ridge, rift, fissures

22. Locations of Divergent Plate Boundaries Mid-Ocean Ridges East Pacific Rise Mid Atlantic Ridge Mid Indian Ridge Mid Arctic Ridge Fig. 1.10 (Mid-Arctic Ridge) East Pacific Rise Mid-Atlantic Ridge Indian Ridge Mid- See Kehew, Figure 2.24

23. 0 30 70 150 300 500 Divergent Plate Boundaries Rifting and generation of shallow earthquakes (<33km) Depth (km) 0 33 70 300 150 500 800

24. Fig. 19.21 Fig. 19.22 Rift Valley Passive continental shelf and rise Rift Valley E.g., Red Sea and East African Rift Valleys Thinning crust, basalt floods, long lakes Shallow Earthquakes Linear sea, uplifted and faulted margins Oceanic Crust See Kehew, Figure 2.33

25. Convergent Plate Boundaries Where plates move toward each other, oceanic crust and the underlying lithosphere is subducted beneath the other plate (with either oceanic crust or continental crust) Wet crust is partially melted to form silicic (Silica- rich, iron-poor, i.e., granitic) magma Stress: Compression Earthquakes Volcanism Rocks Features Lithosphere Simplified Block Diagram Asthenosphere Subducted Plate Oceanic Trench Plate Movement Magma Generation Volcanic Arc Shallow and Deep Earthquakes Lithosphere

26. Convergent Plate Boundary e.g., Pacific Northwest Volcanic Activity Explosive, Composite Volcanoes (e.g., Mt. St. Helens) Arc-shaped mountain ranges Strong Earthquakes Shallow near trench Shallow and Deep over subduction zone Rocks Formed Granite (or Silicic) Iron-poor, Silica-rich Less dense, light colored Usually intrusive: Cooled slowly, deep down, to form large crystals and course grained rock

27. Composite Volcanic Arcs (Granitic, Explosive) Basaltic Volcanism (Non-Explosive) The “Ring of Fire” (e.g., current volcanic activity) A ring of convergent plate boundaries on the Pacific Rim New Zealand Tonga/Samoa Philippines Japanese Isls. Aleutian Island arc and Trench Cascade Range Sierra Madre Andes Mtns. Also: Himalayans to the Alps Indonesia Fujiyama East Pacific Rise Pinatubo Andes Mountains Cascade Range Aleutian Island Arc Siarra Madre Japanese Isls. New Zealand Phillipines.

28. Depth of Earthquakes at convergent plate boundaries Seismicity of the Pacific Rim 1975-1995 0 33 70 300 150 500 800 Shallow quakes at the oceanic trench (<33km) Deep quakes over the subduction zone (>70 km) Depth (km)

29. Each major plate caries a continent except the Pacific Plate. Each ocean has a mid-ocean ridge including the Arctic Ocean. Divergent bounds beneath E. Africa, gulf of California The Pacific Ocean is surrounded by convergent boundaries. Also Himalayans to the Apls See Kehew, Figure 2.24 Major Plates and Boundaries

30. Iceland Kilimanjaro Red Sea Gulf of Aden Etna Visuvius East African Rift Mid-Atlantic Ridge Mid-Indian Ridge Divergent Plate Boundaries Rifting and Formation of new Basiltic Oceanic Crust Oceanic Crust* Thin (<10 km) Young (<200my) Iron Rich (>5%) / Silica Poor (~50%) Dense (~ 3 g/cm 3 ) Low lying (5-11 km deep) Formed at Divergent Plate Boundaries Composite Volcanic Arcs (explosive) Basaltic Volcanism (non-explosive) *Make a “Comparison Table” on a separate page

31. Convergent Plate Boundaries Formation of Granitic Continental Crust Continental Crust Thick (10-50 km) Old (>200 m.y. and up to 3.5 b.y.) Iron Poor (<1%) / Silica Rich (>70%) Less Dense (~ 2.5 g/cm 3 ) High Rising (mostly above see level) Formed at Convergent Plate Boundaries Oceanic Crust Thin (<10 km) Young (<200 my) Iron Rich (~5%) / Silica Poor (~50%) Dense (s.g. ~3 x H 2 O) Low lying (5-11 km deep) Formed at Divergent Plate Boundaries

32. Isostatic Adjustment Why do we see, at the earths surface, Intrusive igneous rocks and Metamorphic rocks Formed many km deep? Thick, light continental crust buoys up even while it erodes Eventually, deep rocks are exposed at the earth’s surface Minerals not in equilibrium weathered (transformed) to clay Sediments are formed

33. The Hydrologic Cycle Works with Plate-Tectonics to Shape the land Weathering clay, silt, sand… Erosion Transport Sedimentation Geologic Materials Sediments Sedimentary Rocks See Kehew Fig. 2.45

34. The 3 rock types form at convergent plate boundaries Igneous Rocks: When rocks melt, Magma is formed, rises, cools and crystallizes. Sedimentary Rocks: All rocks weather and erode to form sediments (e.g., gravel, sand, silt, and clay). When these sediments accumulate they are compressed and cemented (lithified) Metamorphic Rocks: When rocks are compressed and heated but not melted their minerals re-equilibrate (metamorphose) to minerals stable at higher temperatures and pressures Metamorphic Rocks Sedimentary Rocks Magma Igneous Rocks See Kehew, Figure 2.34

35. The Rock Cycle See Kehew, Fig. 2.53

36. Igneous and Sedimentary Rocks at Divergent Boundaries and Passive Margins Igneous Rocks (basalt) are formed at divergent plate boundaries and Mantle Hot Spots. New basaltic, oceanic crust is generated at divergent plate boundaries. Sedimentary Rocks are formed along active and passive continental margins from sediments shed from continents Sedimentary Rocks are formed on continents where a basin forms and sediments accumulate to great thicknesses. E.g., adjacent to mountain ranges and within rift valleys. See Kehew, Figure 2.30

37. “Continental Accretion” How continents are built The Ancestral Atlantic Ocean looked like today’s Pacific Island Arcs Oceanic Trenches Bounding Continents Convergent Boundaries Cause new terrains to collide and be accreted to the old continental Cratons ~500 mya ~400 mya

38. “Continental Accretion” How continents are built Mountains are built during accretion Rocks are folded (bent) and faulted (broken and shifted) Volcanoes continue to form Rocks are metamorphosed in the Cores Mountains Weathering and Erosion of Mountains Sediments are shed and Lithified to produce A venire of Sedimentary rocks ~350 mya ~300 mya ~250 mya

39. Rock Types of Continents

40. Metamorphic Formed by intense pressure and heat Deep within mountain cores Exposed by isostacy and erosion Igneous Magma intruded into cores of mountains Lava extruded at volcanoes Sedimentary Weathered and eroded mountains shed sediments Covering the continental interior with a venire of sedimentary rocks

41. Rock Types of Continents AB A B Virginia / Penn.CanadaOhio Michigan

42. Deciphering the Geology of Ohio Using Steno’s Principles By characterizing the sequence of sedimentary rocks found in Ohio, we can decipher the geologic history preserved in the rocks using the basic principles of geology Sandstone Shale Limestone

43. Deciphering the Geology of Ohio Using Steno’s Principles (~1650s) Uniformitarianism Original Horizontality Original Continuity Superposition Uniformitarianism Original Horizontality Original Continuity Superposition Sandstone Shale Limestone

44. Sedimentary Rocks of Ohio Demonstrate the Use of Steno’s principles Generalized sequence of rocks and ages in millions of years Principle of Uniformitarianism Principle of Original Horizontality Principle of Original Continuity Principle of Superposition 450 380 350 Sandstone Shale Limestone

45. Sedimentary Rocks of Ohio Uplift during the Tertiary period (26 mya) Regional Uplift 450 380 350 Sandstone Shale Limestone Erosion

46. Sedimentary Rocks of Ohio Exposed older rocks in central and western Ohio 450 380 350 Sandstone Shale Limestone Regional Uplift Erosion

47. Sedimentary Rocks of Ohio Forming the Findley Arch (with east flank in eastern Ohio) 450 380 350 Sandstone Shale Limestone Regional Uplift Erosion

48. Sedimentary Rocks of Ohio And the pattern of rocks found across Ohio 450 380 350 Sandstone Shale Limestone Regional Uplift Erosion

49. Sedimentary Rocks of Ohio The oldest rocks are found in southwestern Ohio (along the axis of the Findley Arch) 450 380 350 Sandstone Shale Limestone Regional Uplift Erosion

50. Sedimentary Rocks of Ohio 450 380 350 Sandstone Shale Limestone

51. Sedimentary Rocks of Ohio 450 380 350 Sandstone Shale Limestone

52. Sedimentary Rocks of Ohio 450 380 350 Sandstone Shale Limestone

53. Sedimentary Rocks of Ohio 450 380 350 Sandstone Shale Limestone

54. Sedimentary Rocks of Ohio Sandstone Shale Limestone 450 380 350 Sandstone Shale Limestone

55. Sedimentary Rocks of Ohio Sandstone Shale Limestone 450 380 350 Sandstone Shale Limestone

56. Sedimentary Rocks of Ohio Thus rocks are younger and change lithology (rock type) as you go west or east from Ottawa County Sandstone (325 my) Shale Limestone (400 my)

57. The Geologic Record in the Rocks Sandstone Shale Limestone GneissGranite

58. Relative Age and the “Principles” Uniformitarianism Superposition Original horizontality Lateral continuity Cross cutting relationships Inclusions Sandstone Shale Limestone GneissGraniteGabbro See Figure 8.1 – 8.12

59. Formation of Unconformities 240 million years ago 1.Regional Uplift, Tilting, or folding) causes Erosion 2.Erosion surface indicates gap in geologic record 450 380 350 Sandstone Shale Limestone Gneiss (1,500)Granite (280) Gabbro (790)

60. Formation of an Angular Unconformity Sedimentation (e.g., clay) 220 million years ago 1.Regional Uplift, Tilting (or folding), Erosion 2.Erosion surface, gap in geologic record 3.Continuous Sedimentation 450 380 350 Sandstone Shale Limestone Gneiss (1,500)Granite (280) Gabbro (790)

61. Formation of an Angular Unconformity Sedimentation (e.g., lime mud) Shale (220) 210 million years ago 1.Regional Uplift, Tilting (or folding), Erosion 2.Erosion surface, gap in geologic record 3.Continuous Sedimentation 450 380 350 Sandstone Shale Limestone Gneiss (1,500)Granite (280) Gabbro (790)

62. Formation of an Angular Unconformity Sedimentation (e.g., quartz sand) Limestone (210) 200 million years ago Shale (220) 1.Regional Uplift, Tilting (or folding), Erosion 2.Erosion surface, gap in geologic record 3.Continuous Sedimentation 450 380 350 Sandstone Shale Limestone Gneiss (1,500)Granite (280) Gabbro (790)

63. Formation of an Angular Unconformity Sedimentation (e.g., immature sand) Shale (220) Limestone (210) Quartz Sandstone (200) 190 million years ago 1.Regional Uplift, Tilting (or folding), Erosion 2.Erosion surface, gap in geologic record 3.Continuous Sedimentation 450 380 350 Sandstone Shale Limestone Gneiss (1,500)Granite (280) Gabbro (790)

64. Formation of an Angular Unconformity Shale (220) Limestone (210) Quartz Sandstone (200) 180 million years ago Arkose (190) 1.Regional Uplift, Tilting (or folding), Erosion 2.Erosion surface, gap in geologic record 3.Continuous Sedimentation 450 380 350 Sandstone Shale Limestone Gneiss (1,500)Granite (280) Gabbro (790)

65. Formation of an Angular Unconformity Arkose (190) Shale (220) Limestone (210) Quartz Sandstone (200) 170 million years ago 1.Regional Uplift, Tilting (or folding), Erosion 2.Erosion surface, gap in geologic record 3.Continuous Sedimentation 4.Sedimentation ceases 450 380 350 Sandstone Shale Limestone Gneiss (1,500)Granite (280) Gabbro (790)

66. Formation of a Disconformity Erosion Arkose (190) Shale (220) Limestone (210) Quartz Sandstone (200) 160 million years ago 1.Erosion of horizontal beds 450 380 350 Sandstone Shale Limestone Gneiss (1,500)Granite (280) Gabbro (790)

67. Formation of an Disconformity Shale (220) Limestone (210) Arkose (190) Quartz Sandstone (200) 150 million years ago 1.Erosion of horizontal beds 2.Loss of geologic record (i.e., Arkose) 3.Formation of a horizontal erosion surface Erosion 450 380 350 Sandstone Shale Limestone Gneiss (1,500)Granite (280) Gabbro (790)

68. Formation of an Disconformity Shale (220) Limestone (210) Arkose (190) Quartz Sandstone (200) Sedimentation (e.g., reef) 140 million years ago 1.Erosion of horizontal beds 2.Loss of geologic record (i.e., Arkose) 3.Formation of a horizontal erosion surface 4.Renewed Sedimentation 450 380 350 Sandstone Shale Limestone Gneiss (1,500)Granite (280) Gabbro (790)

69. Formation of an Disconformity Shale (220) Limestone (210) Arkose (190) Quartz Sandstone (200) 130 million years ago 1.Erosion of horizontal beds 2.Loss of geologic record (i.e., Arkose) 3.Formation of a horizontal erosion surface 4.Renewed Sedimentation Limestone (140) 450 380 350 Sandstone Shale Limestone Gneiss (1,500)Granite (280) Gabbro (790)

70. Formation of an Disconformity 450 380 350 Sandstone Shale Limestone Shale (220) Limestone (210) Arkose (190) Quartz Sandstone (200) 120 million years ago 1.Erosion of horizontal beds 2.Loss of geologic record (i.e., Arkose) 3.Formation of a horizontal erosion surface 4.Renewed Sedimentation Limestone (140) Gneiss (1,500)Granite (290) Gabbro (790)

71. Summary: Types of Unconformities Deciphering Relative Ages Principles give sequences of geologic events Unconformities indicate gaps in the geologic record Shale Limestone Quartz Sandstone Limestone Sandstone Shale Limestone GneissGranite Disconformity Angular Unconformity Nonconformities Gabbro

73. The Grand Staircase Correlation Physical Continuity Similar Rock Types Fossils (index and assemblage)