Geology and Earth Resources

1. Geology and Earth Resources

2. A Layered Sphere • Core – dense, intensely hot metal • Mostly Fe and Ni • Inner and Outer Core • Mantle - Hot, pliable layer, less dense • O2, Si, Mg • Mesosphere (lower mantle) • Asthenosphere - warm, ductile, weak, mantle beneath lithosphere • Crust - Cool, lightweight, floats on mantle. (lithosphere)

3. Earth’s Cross Section

4. Lithosphere • Divided into plates (about 13 major plates and several smaller ones).

5. Plate Tectonics • Pangea

9. Plate Boundaries • Defined by earthquake data. • Depths of earthquakes indicate types of boundaries.

10. Plate Boundaries • Divergent Boundaries • Oceanic plates move apart • Seafloor spreading • Magma from mantle pushes up and and out • Convergent Boundaries • 2 plates move toward one another and collide • One oceanic plate sinks below the other creating a deep trench • Denser oceanic plate moves underneath continental plate • Creation of long coastal mountain ranges (Andes) • Volcanoes form “Ring of Fire” • Two continental plates colliding • mid-continental mountain ranges (Himalayas)

11. Plate Boundaries Cont. • Transform Boundaries • Plates slide past each other • Earthquakes • San Andreas Fault

12. Earthquakes • Sudden release of energy in crust creating seismic waves with radiate in all directions from the source (focus) • Epicenter • Energy dissipates with distance • Caused by: • Rupture of geologic faults • Volcanic activity • Major human activity • Mine blasts, nuclear

13. Earthquakes • Types of waves released: • P waves-side to side motion • S waves-up and down motion through earth’s crust • Seismographs-records ground motion • P waves arrive faster than S waves • Richter scale-scale of magnitude

14. Locating the Epicenter of an Earthquake • P, S and surface waves all start out at same time. • The further you are away from the quake, the longer the time span between arrival of P and S wave. • The distance of the seismometer to the earthquake can be determined by the time between the arrival of P wave and arrival of S waves. • Can tell the distance, but not the direction. • Therefore, multiple sites must be used to find epicenter.

15. Earthquakes • Earthquakes do not cause injury or death • 1988 - Soviet Armenia: magnitude 6.9, 25,000 people died • 1985 - Mexico City: magnitude 8.1, 9500 people • 1989 - Loma Prieta, CA: magnitude 7.1, 40 people died • 1995 - Kobe, Japan: magnitude 7, ~6000 people died • 2010 – Haiti: magnitude 7.0, over 100,000 people died • ~800,000 small earthquakes of 2.0 or less per year • 8.0 occurs about once every 10 years

16. Recent World Earthquakes (past 7 days)

17. Anchorage, AK April 1964

18. Anchorage, AK April 1964

19. San Francisco 1906

21. VOLCANOES http://georoc.mpch-mainz.gwdg.de/volcano.gif

22. Volcanoes • Located at plate boundaries • Composite, shield, cinder cones, dome • Result in surface pyroclastic and extrusive igneous rocks

25. Eruptions from Volcanoes • May produce lava rock or ash, molten lava, and/or toxic gases. • Gases: H2O, CO2, SO2, HCl • Pressure within magma chamber forces molten magma up through a conduit and out a vent. • Benefits?

26. Eruption of Mount Saint Helens, May 18, 1980 • Most destructive in US history • Located in southwest Washington in the Cascade Range

32. Geological Cycle • Geological processes - continually modify the Earth’s surface, destroy old rocks (create soil), create new rocks and add to the complexity of ground conditions. • Earth movements are vital to the cycle.

33. Rock Types • Rock Cycle - Cycle of creation, destruction, and metamorphosis. • Three major rock classifications: • Igneous • Sedimentary • Metamorphic

34. Rock Cycle

35. Igneous Rocks • Most common type of rock in earth’s crust. • Solidified from magma from interior • Quick cooling-fine grained rocks • Basalt • Slow cooling- coarse-grained rocks • Granite

36. Sedimentary Rock • Deposited materials remaining in one place long enough, or covered with enough material to compact it-will become rock • Shale, sandstone

37. Metamorphic Rock • Igneous or sedimentary rock that has been subjected to tremendous heat and pressure • Marble (from limestone) • Quartzite (from sandstone) • Slate (from mudstone and shale)

38. Types of Weathering • Physical-mechanical breakdown of rocks and minerals • Caused by water, wind, temp variations • Makes rock more vulnerable to further degradation • Chemical – breakdown of rocks and minerals by chemical reactions, the dissolving of chemical elements from rocks, or both • Natural or man made processes

39. Formation of Soils • From weathering, biological (plants and fungi), chemical (oxidation), and physical (wind, water) • Soils develop in response to • Climate (temperature and moisture) • Living organisms (nutrient cycling) • Parent Material • Topography (drainage, slope, elevation, wind exposure) • Time

40. SoilRenewable or Nonrenewable? • Soil is created at a rate of 10 tons per hectare (2.5 acres) per year under the best conditions • Under poor conditions, it can take thousands of years to form that much soil • Soil is created by natural processes, but we are depleting it at a faster rate than it can be created

41. Major Characteristics of Soil • Soil Chemistry • Soil Composition • Particle Size • Soil Texture • Organisms • Soil Horizons

42. Soil Chemistry • pH • Best between pH 6-8 • Too acidic-add limestone • Too basic-add organic material • Proper pH directly affects the availability of plant food nutrients • Nitrogen • Stimulates above ground growth • Replenished by bacteria (legumes) or fertilizers

43. Soil Chemistry • Phosphorous • Helps to provide a strong root system • Replenished by fertilizer

44. Soil Composition • Particles • Sand (0.05-2 mm), silt (0.02-0.05 mm) and clay (less than 0.02 mm) • Particle size affects soil characteristics • Spaces between sand particles give sandy soil good drainage and allow aeration. • Tight packing of small particles in silt or clay = less permeable to air and water. • Minerals • humus (sticky brown residue from partially decomposed plants and animals) • humus creates “structure” -holds materials together

46. Soil Organisms • Activity of organisms living in the soil help create structure and fertility • Breaking down the organic material • Fungi and bacteria are in the top few cms. • Worms and insects add and cycle nutrients in the soil

47. Soil Profiles • Soil profile-stratified horizontal layers • O Horizon (Organic layer) • Leaf litter, partially decomposed organisms. • A Horizon (Topsoil) • Mineral particles mixed with organic material. • E Horizon (Leached) • Depleted of soluble nutrients. • B Horizon (Subsoil) • Often dense texture from accumulating nutrients. • C Horizon (Parent Material) • Weathered rock fragments with little organic material.