Weathering

What is Weathering?

The process by which rocks and minerals at the Earth's surface are physically and chemically broken down.

Types of Weathering

Mechanical Weathering Disintegration

Breaks rock into smaller pieces.

Abrasion Physical wearing and grinding of a surface through friction.

Mushroom Park

Animal & Plant Lichen works very slowly to break down granite boulders.

Exfoliation The peeling away of large sheets of loosened materials at the surface of a rock.

Frost Wedging

Mt Brewer in the Sierra Nevada

The east ridge of Mt. Brewer

Lab: Frost Wedging

Chemical Weathering Decomposition

Rocks are changed into different materials.

Usual Suspects

Oxygen

Oxidation

Acid Rain

Lab: Acid Rain

Water Weathering

Lab: Effects of Weathering on Various Minerals

Lab: Observe the Chemical Weathering of Feldspar

Mechanical vs. Chemical Mechanical Weathering Changes the size of the rock. Chemical Weathering Changes the composition of the rock.

Factors That Control Weathering Surface Area

Surface Area

Lab: Surface Area vs. Size & Shape

Lab: Chemical Weathering vs. Surface Area

Factors That Control Weathering Composition of Rock

Climate

Lab: Temperature vs. Chemical Weathering

Erosion & Mass Movements

Erosion Removal and transport of materials by wind & running water.

Mass Movement Downward transportation of weathered materials by gravity.

Soil Earth’s Life Supporting Material.

Soil Profile

Soil Profile vs. Time

Soil Age

Soil Composition Refers to the proportions of different particle sizes in the soil.

Sand (less than 2 mm) Silt (less than 1/16 mm) Clay (less than 1/256 mm)

Sandy soils are light and typically very free draining, usually holding water very poorly due to very low organic content. Clay soils tend to be heavy and difficult to work when dry. Clay soils tend to allow virtually all water to run-off.

Soil Texture Triangle

30% clay 20% silt 50% sand 10% clay 70% silt 20% sand 50% clay 20% silt 30% sand Sample A Sample B Sample C Sand Clay Loam Silty Loam Clay

Lab: Are You My Type?

Lab: Soil Texture Feel Test

Soil Texture Feel Test 1 Place about 2 teaspoons of soil in your palm. Add water drop by drop and knead soil until it is moldable and feels like moist putty.

Does the soil remain in a ball when squeezed?

Soil Texture Feel Test 1 SAND No Yes Move to Soil Texture Feel Test 2!

Soil Texture Feel Test 2 Place the ball of soil between your thumb & forefinger. Gently push the soil with thumb, squeezing it upward into a ribbon. Allow the ribbon to emerge and extend over your forefinger until it breaks from its own weight.

Does the soil form a ribbon?

LOAMY SAND No Yes Move to Soil Texture Feel Test 3!

Soil Texture Feel Test 3A Does the soil make a weak ribbon (<1inch long) and feels gritty?

LOAM or SILT LOAM No Yes SANDY LOAM

Soil Texture Feel Test 3B Does the soil make a medium ribbon (1-2 inch long) and feels gritty?

CLAY LOAM or SILT CLAY LOAM No Yes SANDY CLAY LOAM

Soil Texture Feel Test 3C Does the soil make a strong ribbon (>2 inch long) and feels gritty?

CLAY No Yes SANDY CLAY

Porosity Porosity is the percentage of void space in a rock.

Soil Porosity

Lab: Soil Porosity

Lab: Soil Permeability

Soil Erosion

Causes of Soil Erosion

Contour Farming

Strip-Cropping

Windbreaks

Terraces