1. Rocks and Soil

2. What Are Minerals and Rocks?
Naturally occurring compound that exists as a crystalline solid
Mineral resource
Concentration that we can extract and process into raw materials
Rock
Solid combination of one or more minerals

3. What Are Minerals and Rocks?
Sedimentary rock
Made of sediments
Dead plant/animal remains (fossils!)
Tiny particles of weathered and eroded rocks
The sediment gets turned into rock by
Being buried/compacted by weight or rocks
Being cemented together by materials that have been dissolved in water

4. What Are Minerals and Rocks?
Metamorphic rock
Existing rock subjected to high temperatures, pressures, fluids, or a combination
Pressure and heat can come from being buried deep in the earth or from proximity to magma
Igneous rock
Intense heat and pressure, magma wells up from the earth’s mantle, cools & hardens

5. Examples of Igneous Rocks
Pumice
Obsidian
Basalt
Other examples include: Diabase, Diorite, Gabbro, Granite, Rhyolite, Scoria

6. Examples of Sedimentary Rocks
Shale = silt particles
Sandstone = sand particles
Limestone = calcium carbonate or calcite (shells of marine organisms)
Other examples include: Breccia, Conglomerate

7. Examples of Metamorphic Rocks
Marble
Slate
Gneiss
Other examples include: Quartzite, Schist, Serpentinite

8. Earth’s Rocks Are Recycled Very Slowly
Rock cycle
Rocks are recycled over millions of years
Erosion, melting, and metamorphism
Slowest of earth’s cycle processes

9. External Earth’s Processes: Can Lead to Soil
Weathering-breakdown of solid rock
Mechanical (Physical) weathering
Frost Wedging, freeze-thaw cycle
Chemical Weathering
Oxidation (losing/gaining e-)
Hydrolysis (splitting of water)
Erosion-process by which earth particles are moved from one place & deposited in another
Wind -Ice
Water -Gravity

10. Soil is the Foundation of Life on Land
Mixture of eroded rock, mineral nutrients, decaying organic matter, water, air, humus (microorganisms, decaying organic material) & living organisms
Formation begins when
Bedrock is slowly broken into fragments/particles by physical, chemical & biological processes
Pg 290 in book

11. Soil is the Foundation of Life on Land
Key component of earth’s natural capital
Supplies most of nutrients needed for plant growth
Purifies & stores water
Organisms living in it remove CO2 from atmosphere & store it as organic carbon compounds
Helps control earth’s climate

12. Mature Soils Contain horizontal layers “horizons” O horizon A horizon
B horizon
C horizon
Bedrock (base parent material)

13. The Horizons of Soil “O horizon” “A horizon” Leaf litter Upper layer
topsoil
Contain bacteria, fungi, earthworms, small insects
Decomposers break down compounds into “humus” & inorganic materials

14. The Horizons of Soil “B Horizon” “C horizon” subsoil Parent material
Most of inorganic matter-broken down rock containing varying mixtures of sand, silt, clay, gravel
Underneath “C” is the bedrock

15. The Horizons of Soil Spaces (“pores”) contain air or water
As long as “O/A” are anchored by vegetation, the soil layers as a whole act as a sponge, storing water & nutrients!
Topsoil-renewable resource but very slow replenishment rate! (1 cm takes 100s of years to form!)

16. Soil Properties Water Infiltration Leaching
Porosity: amount of pore spaces
Permeability: ability to transmit fluids
2. Texture: the way the soil feels
Depends on amount of each sized particles- termed soil fraction
Sand: larges, gritty
Silt: medium, soft, silky, floury
Clay: small, sticky, hard to squeeze, greatest surface area
Water
High permeability
Low permeability

17. Increasing percentage sand
Soil Properties
100%clay
Increasing
percentage silt
percentage clay 20 40 60 80
100%sand
100%silt
Increasing percentage sand
sandy
clay
silty
silty clay
loam
silt
sandy clay
loamy
sand
Gravel
2-64 mm
Sand mm
Silt mm
Clay
less than mm

18. Soil Properties 3. pH Influences uptake of nutrients by plants
4. Fertility
20 minerals needed for plant growth
Major nutrients = nitrogen, phosphorus & potassium

19. Topsoil Erosion Is a Serious Problem in Parts of the World
Movement of soil by wind and water
Natural causes
Human causes
Two major harmful effects of soil erosion
Loss of soil fertility
Water pollution
12-3, red = serious concern, blue = some concern, white = stable/non vegetative

20. Drought and Human Activities Are Degrading Drylands
Desertification
Productive potential of topsoil falls by 10% or more
Prolonged drought, human activities
Human agriculture accelerates desertification
Dust bowl
Severe wind erosion of topsoil
Combination of poor cultivation practices & prolonged drought

21. Excessive Irrigation Has Serious Consequences
Soil salinization
Gradual accumulation of salts in the soil from irrigation water
Lowers crop yields and can even kill plants
Affects 10% of world croplands
Waterlogging
Saturation of soil with
irrigation water or excess
precipitation
Water table rises close to the
surface

22. Many Farmers Are Reducing Soil Erosion
Soil conservation
Terracing
Contour planting
Strip cropping with cover crop
Alley cropping, agroforestry
Windbreaks or shelterbelts
Conservation-tillage farming
Identify erosion hotspots
12-6

23. We Can Restore Soil Fertility
Organic fertilizer
Animal manure
Green manure
Compost
Manufactured inorganic fertilizer
Nitrogen, phosphorus, and calcium
Crop rotation
12-6

24. US Legislation
Soil Conservation Act of 1935: law organized the Soil Conservation Service which is now called the Natural Resources Council
Food Security Act or Farm Bill of 1985: Law required US farmers to control erosion on land that was subject to large amounts of soil loss
If they failed to do so, lost government price supports for product