Geology and Earth Resources

Transcription

1 Geology and Earth Resources 1

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

3 Earth s Cross Section 3

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

5 Pangea Plate Tectonics 5

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

10 Divergent Boundaries! Oceanic plates move apart! Seafloor spreading Plate Boundaries 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) 10

11 Transform Boundaries! Plates slide past each other - Earthquakes " San Andreas Fault Plate Boundaries Cont. 11

12 Earthquakes Sudden release of energy in crust creating seismic waves-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, fracking 12

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 13

14 Locating the Epicenter of an Earthquake P, S and surface waves all start out at same time. Further you are away, 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. Able to tell distance, but not direction.! Multiple sites must be used to find epicenter 14

15 Earthquakes Earthquakes do not cause injury or death! Soviet Armenia: magnitude 6.9, 25,000 people died! Mexico City: magnitude 8.1, 9500 people! Loma Prieta, CA: magnitude 7.1, 40 people died! 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 15

16 Anchorage AK: March 27,

17 Anchorage, AK: March

18 Anchorage, AK: March 27,

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20 San Francisco,

21 Japan

22 VOLCANOES! 22

23 Volcanoes Located at plate boundaries! Composite, shield, cinder cones, dome Result in surface pyroclastic and extrusive igneous rocks 23

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26 Eruptions from Volcanoes May produce lava rock or ash, molten lava, and/or toxic gases. Gases: H 2 O, CO 2, SO 2, HCl Pressure within magma chamber forces molten magma up through a conduit and out a vent. Benefits? 26

27 Eruption of Mount Saint Helens, May 18, 1980 Most destructive in US history Located in southwest Washington in the Cascade Range 27

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33 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

34 Rock Types Rock Cycle - Cycle of creation, destruction, and metamorphosis.! Three major rock classifications: - Igneous - Sedimentary - Metamorphic 34

35 Rock Cycle 35

36 Igneous Rocks Most common type of rock in earth s crust.! Solidified from magma from interior - Quick cooling-fine grained rocks " Basalt - Slow coolingcoarse-grained rocks " Granite 36

37 Sedimentary Rock Deposited materials remaining in one place long enough, or covered with enough material to compact it - Shale, sandstone 37

38 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

39 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

40 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

41 Soil Renewable 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

42 Soil Chemistry Soil Composition! Particle Size! Soil Texture Organisms Soil Horizons Major Characteristics of Soil 42

43 Soil Chemistry ph! Best between ph 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

44 Soil Chemistry Phosphorous! Helps to provide a strong root system! Replenished by fertilizer 44

45 Particles Soil Composition! Sand ( mm), silt ( 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 45

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47 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

48 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. 48

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