1. The Cycling of Earth’s Rocks
The three major types of rocks found in the earth’s crust—sedimentary, igneous, and metamorphic—are recycled very slowly by the process of erosion, melting, and metamorphism.

2. The crust is composed of rocks & minerals
Minerals- elements or inorganic compounds that occur naturally in the earth’s crust as a solid with a regular internal crystalline structure
Ex: gold, diamond, silver, salt, quartzite
Rocks – a solid combination of one or more minerals found in the earth’s crust
Example: Granite = mica + feldspar + quartz

3. Classifying Rocks
There are three broad classes of rocks, based on formation
Sedimentary (deposited)
Igneous (volcanic)
Metamorphic (heat & pressure) 3

4. There Are Three Major Types of Rocks (1)
Sedimentary -
piling of material
over time (fossil
record)
Sandstone
Shale
Limestone
Bituminous coal 4

5. There Are Three Major Types of Rocks (2)
Igneous - cooling and crystallization of magma
(form the bulk
of the earth’s crust)
Granite
Lava rock
Quartz

6. There Are Three Major Types of Rocks (3)
Metamorphic
(igneous or sed.
subjected to heat
and pressure)
Anthracite
Slate
Marble 6

7. The Earth’s Rocks Are Recycled Very Slowly
Rock cycle
Slowest of the earth’s cyclic processes

8. Heat, pressure, stress Magma (molten rock)
Erosion
Transportation
Weathering
Deposition
Igneous rock
Granite, pumice, basalt
Sedimentary rock Sandstone, limestone
Heat, pressure
Cooling
Heat, pressure, stress
Magma (molten rock)
Figure 14.13
Natural capital: the rock cycle is the slowest of the earth’s cyclic processes. Rocks are recycled over millions of years by three processes: erosion, melting, and metamorphism, which produce sedimentary, igneous, and metamorphic rocks. Rock from any of these classes can be converted to rock of either of the other two classes, or can be recycled within its own class (Concept 14-2). Question: What are three ways in which the rock cycle benefits your lifestyle?
Melting
Metamorphic rock
Slate, marble, gneiss, quartzite
Fig , p. 354

9. Soil Formation The Importance of Soil
All life depends on the thin top layer of soil covering the earth’s surface.
Created when rocks, dead animals or plants break down into tiny pieces
Topsoil provides:
Support
Water
Air
Nutrients
Filter/Buffer

10. Weathering: Biological, Chemical, and Physical Processes

11. Erosion – by wind

12. Erosion – by water

13. Glacier Receding

14. Weathering: Breakdown of Rock near the Surface
Chemical Alteration
Carbon dioxide, sulfur dioxide and various nitrogen compounds from the air form acids when dissolved in water. These acids may react with the rock and increase breakdown.

15. Chemical Weathering

16. Chemical Weathering

17. What Determines Soil Type
Living Organisms
Topography
Climate
Vegetation
Time
Parent Material
Residual - Transported
Least Important Factor for Mature Soils

18. Soil Composition

19. Soil Formation and Generalized Soil Profile19

20. Soil Horizons and Profiles
Soil Profile
Suite of Layers at a Given Locality
Soil Horizons
Layers in Soil
Not Deposited, they are Zones of Chemical Action
Layers (horizons) of mature soils
O horizon: leaf litter
A horizon: topsoil
B horizon: subsoil
C horizon: parent material, often bedrock

22. Principal Soil Horizons
O - Organic (Humus) Often Absent
A – Leaching
K, Mg, Na, Clay Removed
B – Accumulation
Absent in Young Soils
Distinct in Old Soils
Al, Fe, Clay (Moist)
Si, Ca (Arid)
C - Parent Material

23. Soil Characteristics Physical Texture Porosity Permeability Humus
Color
Chemical pH
*You need to know how to fix pH problems
Nitrogen
Phosphorous
Potassium

24. Permeability – the degree to which the pores in the rock or soil are connected together so that water can move freely
Porosity - the percentage of interconnected space in rock and soil that can contain water

25. Main Soil Textures Soil Type Texture Permeability Porosity Sand Gritty
High
Low
Silt
Smooth & Slippery
Med
Clay
Sticky

26. Soil Formation vs. Soil Erosion
Takes hundreds of years to form 1 cm (0.4 inches) of soil
Soil erosion
Blown away in weeks or months from plowing and clearing forests – any time we leave the topsoil unprotected 26

27. Topsoil Erosion Is a Serious Problem in Parts of the World
Two major harmful effects of soil erosion
Loss of soil fertility through depletion of plant nutrients in topsoil
Water pollution in nearby surface waters where eroded soil ends up as sediment
Kills fish, shellfish
Clogs irrigation ditches, reservoirs, lakes, and boat channels
Eroded soil may also be polluted with pesticides and fertilizers

28. Dust Bowl of the 1930’s

29. China’s Dust Storms

30. Soil Textural Triangle Practice Exercises
% Sand % Silt % Clay Texture Name
sandy loam
_______________

31. Reduce Soil Erosion Soil conservation, some methods
Terracing
Contour planting
Strip cropping with cover crop
Alley cropping, agroforestry
Windbreaks or shelterbeds
Conservation-tillage farming
No-till
Minimum tillage
Identify erosion hotspots 31

32. Figure 12.24
Soil conservation methods include (a) terracing, (b) contour planting and strip cropping, (c) alley cropping, and (d) windbreaks (Concept 12-6A).
Fig a, p. 302

33. Figure 12.24
Soil conservation methods include (a) terracing, (b) contour planting and strip cropping, (c) alley cropping, and (d) windbreaks (Concept 12-6A).
Fig b, p. 302

34. Figure 12.24
Soil conservation methods include (a) terracing, (b) contour planting and strip cropping, (c) alley cropping, and (d) windbreaks (Concept 12-6A).
Fig c, p. 302

35. Figure 12.24
Soil conservation methods include (a) terracing, (b) contour planting and strip cropping, (c) alley cropping, and (d) windbreaks (Concept 12-6A).
Fig d, p. 302

36. Solutions: Mixture of Monoculture Crops Planted in Strips on a Farm36

37. Conservation Tillage
Conservation-tillage farming: method of soil cultivation that leaves the previous year's crop residue on fields before & after planting the next crop
No-till: involve planting crops directly into residue that either hasn't been tilled at all
Minimum tillage: some residue has been removed, but at least 30 to 70% remains

38. No Till & Minimum Tillage
Planting into corn residue (no till)
Soybeans grown in striped rows between corn residue (minimum tillage)

39. Benefits of Conservation Tillage
Environmental benefits
Reduces soil erosion by 60%-90% from rain & wind
Improves soil and water quality by adding organic matter as crop residue decomposes
Conserves water by reducing evaporation
Conserves energy due to fewer tractor trips
Reduces air pollution from dust and diesel
Crop residue provides food and cover for wildlife

40. Benefits of Conservation Tillage
Practical benefits
Fewer trips across the fields saves time and money (lowers fuel, labor and machinery maintenance costs) and reduces soil compaction that can reduce yields
Optimizes soil moisture, enhancing crop growth in dry periods or on droughty soils