WEATHERING & SOIL

Weathering  The chemical and physical alterations of rock and other Earth materials at or near earth’s surface, through the action of temperature changes, water, chemical agents, atmospheric gases, and organic materials  Basically, breaking down rocks into smaller pieces

Weathering v Erosion:  Weathering = changing/breaking of Earth materials  Erosion = transport of Earth materials  Examples?

Physical Weathering  The mechanical or physical breakdown of rock and other earth materials at or near earth’s surface into smaller pieces, called sediments  without a change in the mineral/chemical composition Break or crack in rock: is called a “JOINT”

Chemical Weathering  the processes by which chemicals, such as oxygen, acids, and water, break down rocks and other Earth materials  resulting in more stable new minerals (chemicals) CO 2 + H 2 O  HCO 3 (carbonic acid) main erosional agent!!

Rate and Type  Depends on four major variables (yes, write all of this) 1. Exposure – to air, water, and living things 2. Particle size – smaller particles = more surface area = greater weathering rate 3. Mineral composition – marble/limestone easily dissolves 4. Climate – warm, wet climate = more chemical cold, wet = more physical

SOIL  How does soil form? Top soil – decayed organic material, some sand and clay Subsoil – brown from settled iron oxides, contains clay and soluble materials Residual soil – parent material is the bedrock beneath it Transported soil – from moved materials (wind, streams) Parent material – material from which soil is formed (bedrock) Soil profile – cross-section of earth exposed by digging

Important Soil Layers ORGANIC CLAYS BEDROCK RESIDUAL & TRANSPORTED

5 Factors that Effect Soil Composition 1 Time – soil formation takes decades, centuries, or millennia 2 Parent material – chemical and physical attributes of parent material influence properties of the soil formed from it 3 Plants and animals – earthworms and other burrowing animals mix and aerate soil, add organic matter, and speed decomposition Beetle grub, earthworm, fungi, cicada nymph, mites, snails, moles Plants add organic matter and affect a soil’s composition and structure

5 Factors that Effect Soil Composition 4 Topography – hills and valleys affect exposure to sun, wind, and water. Steeper slopes promote runoff and erosion; also slows leaching, accumulation of organic matter, and formation of soil layers 5 Climate – soil forms faster in warm, wet climates. Heat speeds chemical reactions, weathering, decomposition, and growth of organisms. Moisture is required for many biological processes so it speeds weathering

Soil as a Resource FERTILITY DEPLETION Ability to grow plantslacking in nutrients Depends on minerals,cannot support life Organic material content, & water

CONSERVATION METHODS  Windbreaks – planting belts of trees along field edges  Contour farming – planting crops in rows parallel to land contours

CONSERVATION METHODS  Terraces – flattening sloped areas by forming terraces  Strip-cropping – alternating a crop that leaves bare ground between rows with a crop that covers the ground  No-till farming – doing planting, fertilization, and weed control at the same time