1. EARTH SCIENCE NOTES (original notes by Mrs. Schwab)
Weathering & Soil
EARTH SCIENCE NOTES
(original notes by Mrs. Schwab)

2. WHAT IS WEATHERING?
Weathering is a collection of ways that minerals and rocks are broken or worn down into bits and pieces.
The bits and pieces of the original rock are called sediment.

3. CHEMICAL WEATHERING Rocks are chemically changed
New products are formed

4. CHEMICAL WEATHERING (EXAMPLES)
Oxidation – Rust – Iron Oxide
Iron + Oxygen = Iron Oxide
Carbonic Acid
CO Water = Carbonic Acid
Dissolves rocks

5. SPEED OF REACTION The speed at which chemical weathering happens:
increases when weather is:
Warm
Moist

6. MECHANICAL WEATHERING
Physical Weathering
Breakup of rocks to smaller pieces
No new materials
No chemical changes

7. TYPES OF MECHANICAL WEATHERING
Day/Night Cycle
Daytime – rocks heat up & expand
Nighttime – rocks cool & contract
Repeated – cracks form in rocks

8. TYPES OF MECHANICAL WEATHERING
Frost Action (Ice Wedging)
Water seeps into cracks in rock
Water expands when frozen
Ice cracks rock
Water melts
Water seeps further into crack in rock

9. TYPES OF MECHANICAL WEATHERING
Animals
Insects & burrowing animals dig holes into soil
Holes allow water & air to reach rocks
Rocks crack due to water action

10. TYPES OF MECHANICAL WEATHERING
Plant/Tree Roots
Roots move through soil – water & air move down to rock layer – water freezes
Roots move into cracks in rocks
Roots grow – crack gets bigger
Roots split rocks

11. SPEED OF REACTION Weather changes Amount of water
Warm - increase - plant growth/animal movements
Cold – increase - water freezes
Amount of water
Little water – decrease – deserts/polar areas
More water – increase – rainy / snow areas

12. SOIL Rock fragments Organic Material Dirt (slang)
Decomposed plants/animals
Plant roots
Insects & worms
Bacteria
Dirt (slang)

13. SOIL PROFILE Cutaway view of soil layers Mature soil has 3 layers
Layer = Horizon

14. SOIL HORIZONS Horizon A Top Soil Upper most layer of soil
Few rocks – More organic material
Humus - Organic material in soil – gives dark color
Leaching – Minerals carried to lower level by water

15. SOIL HORIZONS Horizon B Subsoil
Larger rock fragments – Little organic material
Some leaching
Lighter color than Horizon A

16. SOIL HORIZONS Horizon C 1st stage of soil
Partly weathered rock – No organic material
Rock chunks – almost no organic

17. SOIL HORIZONS Bedrock - solid unchanged rock Determines soil make-up
Determines soil thickness (speed weathering)

18. WHERE THE BEST SOIL IS River Flood Plains Valley Areas River Deltas
Great Plains

19. WHERE POOR SOIL IS
Mountains
Steep Slopes

20. TYPES OF SOIL Clay Soils Fine Grained Water does not move easily
Feldspar minerals
Aluminum
Common in Bradford County

21. TYPES OF SOIL Sandy Soils Coarse grained Water moves easily
Quartz minerals
Rare in Bradford County

22. HEALTHY SOIL
Soil one of most economically important resources on Earth
Material supports plant life & so all life
Soil is source of nutrients for all plants
16 Elements needed
Air & water provide H,O, N, C
Minerals from rocks P,K,Ca

23. HEALTHY SOIL Erosion Control Soil Conservation keeps soil in place
Decrease nutrient loss
Conserve water in soil

24. SOIL LOSS Erosion of soil is natural process
Soil moves from one place to another
Slow process

25. CAUSES OF SOIL LOSS Removal of plant cover (Plowing, Construction)
Overgrazing
Desertification
Forest Harvest (cutting trees)
Floods

26. PREVENTION OF SOIL LOSS
Crop Rotation
Each year plant different crop in field
Each crop removes/replaces different minerals
Recycle old nutrients
Corn - oats - clover

27. PREVENTION OF SOIL LOSS
Contour Plowing
Plant across direction of water flow
Plant across slope NOT up/down
Reduces water erosion - runoff

28. PREVENTION OF SOIL LOSS
Strip Cropping
Alternating sections of crop
Corn – grain
Terracing
Step cropping on a slope
Grape Vines – Rice in China
No-Till Farming
Harvest but do not plow in fall