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Weathering v Erosion: Weathering = changing/breaking of Earth materials Erosion = transport of Earth materials Examples?
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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)
CO2 + H2O HCO3 (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 things2. Particle size – smaller particles = more surface area = greater weathering rate3. Mineral composition – marble/limestone easily dissolves
4. Climate – warm, wet climate = more chemicalcold, wet = more physical
SOIL How does soil form?
Top soil – decayed organic material, some sand and claySubsoil – brown from settled iron oxides, contains clay and soluble materialsResidual 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
http://www.seafriends.org.nz/enviro/soil/geosoil.htm
ORGANIC
CLAYS
BEDROCK
RESIDUAL & TRANSPORTE
D
5 Factors that Effect Soil Composition1 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 Composition4 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 ResourceFERTILITY DEPLETION
Ability to grow plants lacking in nutrientsDepends on minerals, cannot support lifeOrganic 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