Geology

1. Geology

2. Earth’s Structure • Name the zones of the earth • Crust, mantle, core • Now do it again with more detail • Crust, lithosphere, asthenosphere, mantle, outer core, inner core

3. 35 km (21 mi.) avg., 1,200˚C Crust 100 km (60 mi.) 200 km (120 mi.) Low-velocity zone Crust Mantle Lithosphere Solid 10 to 65km 2,900km (1,800 mi.) 3,700˚C Asthenosphere (depth unknown) 100 km Outer core (liquid) 200 km Core 5,200 km (3,100 mi.), 4,300˚C Inner core (solid) Fig. 10.2, p. 212

4. What is in each zone • Core – mostly iron and a little nickel, inner solid and outer is liquid • Mantle – mostly iron, silicon, oxygen, and magnesium, mostly rigid except near surface which is plastic (asthenosphere) • Crust – mostly oxygen, silicon, aluminum, and iron (by weight)

5. Convection below • Heat from the formation of the earth combined with energy from radioactive decay gives way to convection currents of rock (very slow) or mantle plumes in which hot rock rises

6. Plate tectonics • The lithosphere is broken into many large plates which move due to convection currents within the asthenosphere • Remember continental drift (Pangaea)

7. Divergent ( ) and transform fault ( ) boundaries Reykjanes Ridge EURASIAN PLATE EURASIAN PLATE Mid- Atlantic Ocean Ridge ANATOLIAN PLATE JUAN DE FUCA PLATE NORTH AMERICAN PLATE CARIBBEAN PLATE CHINA SUBPLATE Transform fault ARABIAN PLATE PHILIPINE PLATE PACIFIC PLATE AFRICAN PLATE COCOS PLATE Mid- Indian Ocean Ridge Transform fault SOUTH AMERICAN PLATE Carlsberg Ridge East Pacific Rise AFRICAN PLATE INDIAN-AUSTRLIAN PLATE Southeast Indian Ocean Ridge Transform fault Southwest Indian Ocean Ridge ANTARCTIC PLATE Plate motion at convergent plate boundaries Plate motion at divergent plate boundaries Convergent plate boundaries Fig. 10.5b, p. 214

8. Plate boundaries • Divergent – plates move apart, form mid ocean ridges • Convergent – plates slam together, form largest mountains in the world • Subduction is a type of convergent where one plate dives beneath another and usually creates trenches and volcanoes nearby • Transverse – slide sideways past each other (San Andreas Fault)

9. Trench Volcanic island arc Lithosphere Rising magma Asthenosphere Subduction zone Trench and volcanic island arc at a convergent plate boundary Fig. 10.6b, p. 215

10. Fracture zone Transform fault Lithosphere Asthenosphere Transform fault connecting two divergent plate boundaries Fig. 10.6c, p. 215

11. Lithosphere Asthenosphere Oceanic ridge at a divergent plate boundary Fig. 10.6a, p. 215

12. Abyssal hills Folded mountain belt Abyssal floor Oceanic ridge Abyssal floor Trench Craton Volcanoes Continental rise Oceanic crust (lithosphere) Continental slope Abyssal plain Continental shelf Abyssal plain Continental crust (lithosphere) Mantle (lithosphere) Mantle (lithosphere) Mantle (asthenosphere) Fig. 10.3, p. 213

13. Erosion and Weathering • These are the external processes • Erosion is the moving of rock material from one place to another (deposition) • Weathering is the breaking down of rock by natural forces • Ice wedging, rain, wind, gravity • Chemical weathering, carbonic acid

14. Lake Tidal flat Glacier Spits Shallow marine environment Stream Barrier islands Lagoon Dunes Delta Dunes Beach Shallow marine environment Volcanic island Coral reef Continental shelf Continental slope Abyssal plain Deep-sea fan Continental rise Fig. 10.7, p. 216

15. Rocks and minerals • Mineral – an element or inorganic compound that occurs naturally, is solid, and has a regular crystalline internal structure • Rock – type of music meant to be played loud, also any material that makes up a large, natural, continuous part of the earth’s crust

16. Types of rock • Igneous • Granite, pumice, basalt • Sedimentary • Shale, sandstone, limestone (coral reef) • Metamorphic • Slate, marble, quartzite

17. Sedimentary Rock Slate, sandstone, limestone Deposition Transportation Erosion Heat, pressure, stress Weathering EXTERNAL PROCESSES INTERNAL PROCESSES Igneous Rock Granite, pumice, basalt Metamorphic Rock Slate, marble, quartzite Heat, pressure Cooling Melting Magma (molten rock) Fig. 10.8, p. 217

18. Earthquake • Fault – break in the lithosphere • Focus – where the earthquake took place • Epicenter – location above focus at surface • Richter scale – used to measure magnitude, less than 3 is not felt, logarithmic scale, so each increase of 1 is a factor of 10 • Minor < 5, damaging 5-6, destructive 6-7, major 7-8, great over 8 • Aftershock – reduced shaking after original movement

19. Volcano – it can happen here! • Volcano - Wherever magma reaches the surface through a vent or fissure (also released are gases carbon dioxide, water vapor, hydrogen sulfide, ash, and other ejecta • Mt. St. Helens – worst US volcano disaster • Ring of fire – other than a song by Social D, this is the edge of the pacific plate where most volcanoes are located

20. Soil • Produced slowly (200-1000 years typically) by weathering of rock, deposition of sediments, and decomposition of organic matter • Soil horizons – separate zones within soil • Soil profile – cross-section view of soil

21. Horizons • O horizon – surface litter • A horizon – top soil, made up of inorganic particles (clay, silt, sand) and humus (organic particles from decomposed organisms) • Dark topsoil is richer in nutrients • Releases water and nutrients slowly • Provides aeration to roots • Healthy soil contains many nematodes and bacteria, fungi, etc.

22. Lords and ladies Oaktree Word sorrel Dog violet Organic debris Builds up Earthworm Grasses and small shrubs Rock fragments Millipede Mole Moss and lichen Fern Honey fungus O horizon Leaf litter A horizon Topsoil Bedrock B horizon Subsoil Immature soil Regolith Young soil Pseudoscorpion C horizon Parent material Mite Nematode Actinomycetes Root system Red earth mite Fungus Springtail Mature soil Bacteria Fig. 10.12, p. 220

23. Poor topsoil • Grey, yellow and red are not the colors of healthy topsoil • Generally means that soil is lacking nutrients • Best soil is called loam with equal parts sand, silt, clay and humus • Leaching – dissolving and carrying nutrients (or pollutants) through soil into lower layers

24. B – horizon and C - horizon • B – Subsoil mostly broken down rock with little organic matter • C- parent material broken down rock on top of the bedrock

25. Soils • Texture – relative amount of different sized particles present (sand, silt, clay) • Porosity – volume of pore space in the soil • Permeability – the ability of water to flow through the soil

26. Water Water High permeability Low permeability Sandy soil Clay soil

27. Soils • Clay – high porosity, low permeability • Sand – high permeability, low porosity • Acidity is another factor • Where rain is low, calcium and other alkaline compounds may build up (sulfur can be added – turns to sulfuric acid by bacteria)

28. Forest litter leaf mold Acid litter and humus Acidic light- colored humus Humus-mineral mixture Light-colored and acidic Light, grayish- brown, silt loam Iron and aluminum compounds mixed with clay Dark brown Firm clay Humus and iron and aluminum compounds Tropical Rain Forest Soil (humid, tropical climate) Deciduous Forest Soil (humid, mild climate) Coniferous Forest Soil (humid, cold climate) Fig. 10.15b, p. 223

29. Mosaic of closely packed pebbles, boulders Alkaline, dark, and rich in humus Weak humus- mineral mixture Dry, brown to reddish-brown with variable accumulations of clay, calcium carbonate, and soluble salts Clay, calcium compounds Desert Soil (hot, dry climate) Grassland Soil (semiarid climate) Fig. 10.15a, p. 223

30. Soil erosion • Causes – mainly water and wind • Human induced causes – farming, logging, mining, construction, overgrazing by livestock, off-road vehicles, burning, and more (go us!)

31. Soil erosion • Types • Sheet • Uniform loss of soil, usually when water crosses a flat field • Rill • Fast flowing water cuts small rivulets in soil • Gully • Rivulets join to become larger, channel becomes wider and deeper, usually on steeper slopes or where water moves fast

32. Global soil loss • This is a major problem world wide • Have lost about 15% of land for agriculture to soil erosion • Overgrazing • Deforestation • Unsustainable farming • Also 40% of ag land is seriously degraded due to soil erosion, salinization, water logging and compaction

33. Moderate Severe Very Severe Fig. 10.21, p. 228 Desertification of arid and semiarid lands

34. Areas of serious concern Areas of some concern Stable or nonvegetative areas Global soil erosion Fig. 10.19, p. 226

35. Desertification • Turning productive (fertile) soil into less productive soil (10% loss or more) • Overgrazing • Deforestation • Surface mining • Poor irrigation techniques • Poor farming techniques • Soil compaction

36. Salinization • As water flows over the land, salts are leached out • When water irrigates a field it is left to evaporate typically • This repeated process causes the dissolved salts to accumulate and possibly severely reduce plant productivity • Fields must be repeatedly flushed with fresh water to remove salt build up

37. Waterlogging • When fields are irrigated they allow water to sink into the soil. • Winds can dry the surface • As more water is applied the root area of plants is over saturated reducing yield • As clay is brought to subsoil levels it can act as a boundary for water infiltration

38. Evaporation Transpiration Evaporation Evaporation Waterlogging Less permeable clay layer Fig. 10.22, p. 229

39. Soil conservation • Conservation tillage – (no till farming) disturb the soil as little as possible • Reducing erosion also helps – save fuel, cut costs, hold water, avoid compaction, allow more crops to be grown, increase yields, reduce release of carbon dioxide

40. Soil conservation • Terracing – making flat growing areas on hillsides • Contour farming – planting crops perpendicular to the hill slope, not parallel • Strip cropping – planting alternating rows of crops to replace lost soil nutrients (legumes) • Alley cropping – planting crops between rows of trees

41. Control planting and strip cropping Fig. 10.24b, p. 230

42. Alley cropping Fig. 10.24c, p. 230

43. Fig. 10.24a, p. 230 Terracing

44. Soil conservation • Gully reclamation – seeding with fast growing native grasses, slows erosion or “reverses” it • Also building small dams traps sediments • Building channels to divert water or slow water • Windbreaks – trees planted around open land to prevent erosion • Retains soil moisture (shade, less wind) • Habitats for birds, bees, etc. • Land classification – identify marginal land that should not be farmed

45. Windbreaks Fig. 10.24d, p. 230

46. Soil fertility • Inorganic fertilizers – easily transported, stored, and applied • Do not add humus – less water and air holding ability, leads to compaction • Only supply about 3 of 20 needed nutrients • Requires large amount of energy for production • Releases nitrous oxide (N2O) during production, a green house gas

47. Soil fertility • Organic fertilizers – the odor is a problem • Animal manure – difficult to collect and transfer easily, hard to store • Green manure – compost, aerates soil, improves water retention, recycles nutrients • Crop rotation – allows nutrients to return to soil, otherwise same crop continually strips same nutrient, keeps yields high, reduces erosion

48. See you on the farm! • Remember without farming we all starve • But unless we change our farming practice we continue to damage our environment