Geology and the Environment


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Geology and the Environment

  1. 1. GEOLOGY AND THE ENVIRONMENT The Walker School Environmental Science
  2. 2. Earth’s Principal Systems  Atmosphere  Hydrosphere  Biosphere  Lithosphere  Magnetosphere  Cryosphere
  3. 3. Interaction Among Earth’s Systems Table 1-1, p. 4
  4. 4. Earth is a Dynamic Planet  Geologic Hazards  Renewable Soil  Nonrenewable Minerals  Energy Resources Change is the Norm
  6. 6. Earth’s Structure The Moho, is the boundary between the Earth's crust and the mantle. The Moho serves to separate both oceanic crust and continental crust from underlying mantle.
  7. 7. Seismic S & P Waves Seismic waves provide evidence that Earth’s internal structure is layered, not homogeneous. Fig. 11-9b, p. 345
  8. 8. Internal Processes  Convection Cells  Mantle Plumbs (upwellings)  Plutonic Bodies
  9. 9. Plutonic Bodies L: inflated sills. B: > 100 km2 Internal Processes S: <100 km2 Fig. 4-24, p. 123
  10. 10. Volcanic Bodies External Processes
  11. 11. Mantle Plumbs and Interplate Hotspots Mantle plumbs are stationary, while the plates move. This activity has caused the creation of new Hawaiian Islands over the past 12 million years. Fig. 2-22, p. 58
  12. 12. Volcanic National Park, HI Most geographically isolated group of islands on Earth; features include new cinder cones, glowing pit Lava Tube in Hawaii craters, rivers of lava and fountains of spatter; volcanic features at mass to the lithosphere, water to the hydrosphere, carbon dioxide to the atmosphere, and nutrients for plants. Fig. 5-3a, p. 137
  14. 14. Earth’s crust is about 5% of it’s mass.
  15. 15. Earth has 15 Major Plates Fig. 1-11, p. 17
  16. 16. Environmental Role of Plate Movement  Changes Climate  Stimulates Evolution  Changes Migratory Patterns Scope of the last Ice Age, 1200 BCE
  17. 17. Major Features of the Earth’s Crust Abyssal Abyssal plain Folded mountain belt hills Abyssal Oceanic Abyssal Trench floor ridge floor Craton Volcanoes Continental Oceanic crust rise (lithosphere) Continental Mantle (lithosphere) slope Mantle Continental (lithosphere) shelf Abyssal plain Continental crust Mantle (asthenosphere) (lithosphere) Convection from the Earth’s mantle rises and cools, driving the movement of the plates, which in turn causes the folding of the lithosphere creating mountains and volcanoes.
  18. 18. Connections, Plates and Earth Systems Table 1-3, p. 18
  19. 19. Convergent Plates Primarily responsible for mountain building events. Fig. 2-18c, p. 53
  20. 20. Continental Crust Composed of many rock types. Can be as old as 4 billion years. Varies in thickness from 20 to 80 km. Makes up about 41% of Earth’s surface.
  21. 21. Grand Teton National Park, WY The Grand Tetons are one of the younger mountain ranges on Earth. 24% of the Earth's land mass is mountainous. 10% of people live in mountainous regions. Most of the world's rivers are fed from mountain sources, and A mountain is usually produced by the more than half of humanity depends on movement of lithospheric plates, mountains for water. called orogenic movement.
  22. 22. Alpine Climate Zones Altitude Mountain Ice and snow Tundra (herbs, lichens, mosses) Latitude Coniferous Forest Deciduous Forest Tropical Forest Tundra (herbs, Polar ice Tropical Deciduous Coniferous and snow Forest lichens, mosses) Forest Forest
  23. 23. Divergent Plates Builds new crust. Atlanta Ocean is getting bigger, while the Pacific is decreasing in size.
  24. 24. Mid-Atlantic Ridge & Iceland One of the few places on earth that a divergent pate is evident on land.
  25. 25. Divergent Plates Rift to Form Oceans Rifting between the African and Arabian Plate formed the Red Sea. Fig. 2-15, p. 48
  26. 26. Stages of Ocean Basin Formation
  27. 27. Oceanic Crust 5 to 8 km thick. Composed mainly of basalt and gabbro. Not older than 180 million years. Covered with dead organism and sediment, about 1 km thick. Little variability in composition.
  28. 28. Costal Features Lake Glacier Tidal Shallow marine Spits Stream flat environment Barrier Dunes Lagoon islands Delta Dunes Beach Shallow marine environment Volcanic island Coral reef Continental shelf Continental slope Abyssal plain Deep-sea fan Continental rise
  30. 30. Weathering vs. Erosion  Weathering the decomposition of earth rocks, soils and their minerals through direct contact with the planet's atmosphere. Weathering occurs in situ, or quot;with no movementquot;, and thus should not to be confused with erosion, which involves the movement and disintegration of rocks and minerals by agents such as water, ice, wind, and gravity.
  31. 31. Formation of the Grand Canyon Debris flows shown in this clip erode rock along the walls of the canyon.
  32. 32. Arches National Park Erosion takes place at different rates – called differential erosion Produces: hoodoos, spires, arches, and pedestals Fig. 6-CO, pp. 168-169
  33. 33. Hoodoos, Bryson Canyon National Park
  34. 34. Types of Weathering  Mechanical  Chemical  Biological Weathering of Granite Fig. 6-1a, p. 170
  35. 35. Physical Weathering  Mechanical or physical weathering involves the breakdown of rocks and soils through direct contact with atmospheric conditions such as heat, water, ice and pressure. Badlands, SD
  36. 36. Chemical Weathering  Chemical weathering, involves the direct effect of atmospheric chemicals, or biologically produced chemicals (also known as biological weathering), Lichens are part fungi and part algae. They in the breakdown of derive their nutrients from the rock and rocks, soils and minerals. contribute to chemical weathering.
  37. 37. Biological Weathering from Plants Trees and other plants in Lassen Volcanic National Park, CA help break down parent material into smaller pieces and contribute to mechanical weathering. Fig. 6-6b, p. 174
  38. 38. Salt Weathering (haloclasty)  Mechanical  Derives from an external source (capillary rising ground water, eolian origin, sea water along rocky coasts, atmospheric pollution).  Favored by dry conditions in arid climates.  The expanding salt crystals exert a pressure on the walls of the rock pores that exceeds the tensile Marine Abrasion of Granite. strength of the rock.
  39. 39. Isotasic Rebound from Glaciers Grosser Aletschgletscher, Switzerland Fig. 11-17, p. 351
  41. 41. Earthquakes  Most occur along subduction zones and strike-slip zones  Some occur in aseismic zones  Movement of magma causes tremors
  42. 42. Elastic Rebound Theory  Proposed by Henry F Reid in 1910  Rocks along a fault move relative to each other and can bend elastically  Energy released from the bending causes shock waves, which emanate from the plane of rupture
  43. 43. Two adjoining plates Liquefaction of move laterally along recent sediments the fault line causes buildings Earth movements of sink cause flooding in low-lying areas Landslides may occur on hilly ground Shock waves Epicenter Focus
  45. 45. Measurements  Intensity  Amplitude  Duration
  46. 46. Scales  Richter Scale  Measurement of energy released for smaller and approximate earthquakes  Surface Wave Magnitude Scale  Measurement of energy released for extremely large earthquakes at a distance  Moment Magnitude Scale  Estimates the amount of displacement and area of rupture along the fault  Mercalli Scale  Directly describes the intensity of shaking rather than the magnitude  Useful in comparing damage from earthquakes at different locations
  47. 47. Seismographic Reading
  48. 48. Seismic Wave and Their Destructive Patterns.
  49. 49. Primary Modes of Destruction  Consolidation  Liquefaction  Vibration Earthquake damage in a Afghan village.
  50. 50. Secondary Effects of Earthquakes  Rockslides  Urban Fires  Flooding  Tsunamis  Building Damage  Loss of Life
  51. 51. Expected Damage From Earthquakes No damage expected Canada Minimal damage Moderate damage Severe damage United States
  52. 52. Global Seismograph Network
  53. 53. Indian Ocean Earthquake
  54. 54. Tsunamis  A series of waves created when a body of water, such as an ocean, is rapidly displaced.  Earthquakes, mass movements above or below water, some volcanic eruptions and other underwater explosions, landslides, underwater earthquakes, large asteroid impacts and testing with nuclear weapons at sea all have the potential to generate a tsunami.  As the tsunami approaches the coast and the waters become shallow, the wave is compressed due to wave shoaling and its forward travel slows and its amplitude grows enormously, producing a distinctly visible wave.
  55. 55. Tsunami Warning System
  57. 57. Distribution of Volcanoes  Circum-Pacific Belt (60%)  Mediterranean Belt (20%)  Mid-Oceanic Ridges (20%)  More common along both divergent than convergent plate boundaries.  Mainly composed of intrusive magma flows.  Composed of mafic magma that forms beneath spreading plates.  Pyroclastic materials are not common because lava is fluid.  Water pressure prevents gasses from expanding and escaping. Fig. 5-20, p. 151
  58. 58. General Structure extinct volcanoes central vent magma magma reservoir conduit Solid lithosphere Upwelling magma Partially molten asthenosphere
  59. 59. Crater Lake, OR Caldera Caldera Floor of Crater Lake Wizard Island, Crater Lake, OR
  60. 60. Learn About Megavolcanos Around the World
  62. 62. Important Monitoring Techniques Fig. 5-23, p. 159
  63. 63. Fumarole Gas Monitoring  Chemically-selective sensors for SO2 and CO2 measure gas concentrations and a wind sensor measures wind speed and direction.  Data from solar-powered stations are transmitted to GOES geostationary satellite and then down to observatories every 10 minutes, providing near real time data on degassing of volcanoes
  64. 64. Ground Deformation Monitoring  Paint  Electronic Distance Meters  determine the horizontal movements that occur on active volcanoes  Tiltmeters  leveling surveys to measure vertical motions  Global Positioning Systems  allows us to measure horizontal motions much more accurately and conveniently, and also to estimate vertical motions in the same survey
  65. 65. Remote Sensing  The Advanced Very High Resolution Radiometer (AVHRR) is a space-borne sensor embarked on the NOAA family of polar orbiting platforms.  The primary purpose of these instruments is to monitor clouds and to measure the thermal emission (cooling) of the Earth.  The main difficulty associated with these investigations is to properly deal with the many limitations of these instruments, especially in the early period (sensor calibration, orbital drift, limited spectral and directional sampling, etc).
  66. 66. Primary Effects of Volcanoes  Pyroclastic Flows  Fumaroles  Landslides  Ash Fall  Earthquakes  High Temperatures
  67. 67. Secondary Effects of Explosions  Suffocation from Ash  Asphyxiation from Volcanic Gasses  Tsunamis  Temperatures Decreases Ash can coat your lungs, causing the formation of a quick cement, asphyxiating you.
  68. 68. Environmental Effects  Involved in the formation of continental crust and offset weathering and erosion  Provide nutrient rich soils  By trapping clouds at their peaks, water for agriculture  Agriculture based Volcanic soils in Sumatra. cultures are attracted to their bases
  69. 69. Volcanic Gasses  Water Vapor  Carbon Dioxide  Nitrogen  Sulfur Dioxide  Hydrogen Sulfide  Carbon Monoxide  Hydrogen  Chlorine Gasses emitted from fumaroles at the Sulfur Works in Lassen Volcanic National Park, CA Fig. 5-2, p. 136
  70. 70. Effects of Volcanoes on Climate  Nucleation, condensation, and sedimentation of aerosols (acid rain)  Change in Albedo from ash cloud  Tropospheric cooling from the addition of sulfur to the stratsophere  Ozone destruction through the formation of atomic chlorine
  72. 72. Hydrothermal Vents  Distributes heat and drives water circulation in the ocean through convection  Provides energy source in the form of hydrogen sulfide to benthic chemotrophs  Distributes minerals and influences the composition of the ocean
  73. 73. Hydrothermal Vent Ecosystem The chemosynthetic bacteria grow into a thick mat which attracts other organisms such as amphipods and copepods which graze upon the bacteria directly. Larger organisms such as snails, shrimp, crabs, tube worms, fish, and octopuses form a food chain of predator and prey relationships above the primary consumers. The main families of organisms found around seafloor vents are annelids, pogonophorans, gastropods, and crustaceans, with large bivalves, vestimentiferan worms, and quot;eyelessquot; shrimp making up the bulk of non- microbial organisms.
  74. 74. Location of Major Vent Systems
  75. 75. Hydrothermal Vent Chemistry
  76. 76. Learn More About Vents