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