1. Weathering & Soil

2. Weathering dark Weathering & its effects
Surface processes that break down rock.
Sediments: sand, silt, & clay
Weathering changes the Earth’s surface.
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3. Mechanical Weathering
Occurs when rocks are broken apart by physical processes.
Caused by:
Growing plants
Burrowing animals
Expanding ice

4. Ice wedging occurs where water enters cracks in rocks, freezes, & expands.
As surface area increases, more rock is exposed to be weathered.
Chemical Weathering
Chemicals dissolve the minerals in rocks or change them into different minerals.
Naturally formed acids can weather rocks chemically

5. Carbonic acid forms when Carbon dioxide mixes with water
Carbonic acid forms when Carbon dioxide mixes with water. The acid reacts with calcite in limestone to form caves.
Some roots & decaying plants give off acids that dissolve minerals in rock.
Oxidation occurs when some materials are exposed to oxygen and water. (Rust)

6. Soil Effects of Climate
Mechanical weathering occurs more in cold climates.
Chemical weathering occurs more in warm, wet climates.
Rock type can affect the rate of weathering in a particular climate.
Soil
A. Formation of Soil
Weathering gradually breaks rocks into smaller and smaller fragments.
Plants and animals add organic matter to the rock fragments.

7. Soil is a mixture of
Weathered rock
Decayed organic matter
Mineral fragments
Water
Air
Causes for soil formation include:
Climate
Slope
Types of rock
Types of vegetation
Length of time that rock has been weathering

8. Composition of Soil
Decayed organic matter turns into a dark-colored material called humus.
Humus provides nutrients for plants.
Burrowing creatures mix humus with the other rock fragments.

9. Soil Profile
A Horizon (topsoil)
Can be covered by litter, organic material that will eventually become humus and helps prevent erosion.
B Horizon
Lighter in color & contains less humus.
Leeching is the removal of minerals that have been dissolved by water.
Water reacts with humus & carbon dioxide to form acid.

10. C Horizon
Made of partially weathered rock and is found at the bottom of a soil profile.

11. Soil Types
Different types of soil vary in color, depth, texture, & fertility.
The type of soil depends on the region’s climate.
Deserts are dry, prairies are semi-dry, & temperate forests are mild & moist.

12. Soil Erosion Soil – An Important Resource
Soil is eroded when it is moved to a new location by wind or water.
Soil erosion removes topsoil that is important for plant growth.

13. Causes and Effects of Soil Erosion
Human activities can increase the rate of soil erosion.
Soil erosion occurs rapidly on steep slopes and areas that are not covered by vegetation.
Forest harvesting & overgrazing contribute to the rate at which erosion can occur.

14. Preventing Soil Erosion
Farmers reduce erosion by planting shelter belts, using no-till farming, and planting cover crops after harvesting.
Contour farming and terracing are used to control erosion on slopes.

15. Rows of trees (windbreaks) are
Rows of trees (windbreaks) are planted on the plains to reduce erosion caused by wind.