1. Erosion, Deposition AND SOIL FORMATION
Actions That Change Earth’s Surface

2. Weathering: a review…
Physical or Chemical processes that break down rocks.
Mechanical weathering: ice wedging, root pry, exfoliation, etc.
Chemical weathering: oxidation (iron + oxygen + water = rust), acid precipitation (from burning fossil fuels: sulfur, carbon dioxide, and nitrogen), plant acids (lichens)

3. What affects the rate of weathering?
The type of rock: mineral composition
Surface area: smaller rocks have a greater surface area and weather faster
Climate (temperature and precipitation): hot/warm and wet/humid weather fastest

4. What is erosion?
Erosion is the transport (movement) of weathered rocks and sediment from one place to another.
Erosion is usually gradual…
Humans can speed it up.

5. What are the agents of erosion?
Wind
Water
Waves
Glaciers (ice)
Gravity (mass movement, mass wasting)

6. What is deposition? What goes up must come down.
What is carried must be… dropped.
Deposition occurs when agents of erosion deposit (lay down, drop) sediment.

7. How does gravity change Earth’s surface?
Rapid Mass Wasting…
Landslide
Mudflow

8. Erosion and Deposition
Gravity- pulls materials downhill
Running Water- water has great power
Rill erosion- water running in small channels down a slope
Gulley- When a channel becomes deep and wide

9. How does slow mass wasting erode rocks?
Creep
Slump

10. How does water change Earth's surface?
Running water
Load deposits

11. How is a river's load deposited?
Delta Alluvial fan

12. How do waves change Earth's surface?
Sand bars
Longshore drift

13. Coastal Deposition & Erosion
Much of what is weathered is carried to a coast
When a river hits the oceans, it slows down, dropping its load of sediment
Ocean waves, currents, and tide continue erosion

14. How do glaciers change Earth's surface?
Large mass of moving ice and snow
Abrasion

15. Glacial Erosion Currently Cover <10% of Earth
Very Powerful, polish grind, scratch surfaces
Form valleys, waterfalls, lakes

16. How does wind change Earth's surface?
Sand dunes

17. Wind Erosion
Major forces where low precipitation, high temperature and no plant cover = sandblasting

18. Plants, Animals and People
Move soil around
Buildings, highways, etc.

19. Formation of Soil
Soil- loose covering of broken rock, decaying organic matter (humus) covering Earth’s surface
Soil Formation-
Beginning: weathering breaks solid bedrock into smaller pieces
Organic (living) matter added; organisms die, decay (decomposers)

20. Soil Composition Parent Material- bedrock “gives birth to soil”
Residual Soil- just above parent material
Transported Soil- soil moved to a location far away from parent bedrock
Think Running Water, Wind, Glaciers

21. Soil Profiles- a vertical sequence of layers
Horizons- distinct layers of soil
O- All leaf litter, top layer
A- organic mixed with rock fragments
B- Sub Soil, rich in clay
C- between B and bedrock, mostly broken pieces of rock
Topography affects thickness of soil, hillsides loose soil to erosion

22. Soil Textures Clay- smallest particles Silt- slightly larger
Sand- larger
Loam- combination of the three

23. Soil Fertility How well a soil can support plant growth Factors
Mineral/nutrients, microorganisms, precipitation, topography and acidity
Fertilizer adds nitrates, potassium, phosphorus
Legumes (peas and beans) add microorganisms and nitrates to soil as they grow

24. What caused the Dust Bowl in the 1930s?
Poor soil conservation…