rock cycle and soil. minerals elements or inorganic compounds that occur naturally and are solid...
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Rock Cycle and Soil
Minerals
Elements or inorganic compounds that occur naturally and are solid
Usually have crystalline structure
Almost all of Earth’s crust made of minerals
Rock Cycle
Interaction of processes that change rocks from one type to another
Recycles material over millions of years
Slowest of the earth’s cyclic processes
The Rock CycleThe Rock Cycle
Three Classifications of Rock
Igneous
Sedimentary
Metamorphic
Igneous Rocks
Form from molten rock material (magma) near the surface
Underground igneous rocks are called igneous intrusions, granite
Magma that reaches the surface & cools is called extrusive igneous rock, basalt or pumice
Sedimentary Rocks
Weathered materials that has been deposited in layers and has undergone compaction
Make up 75% of earth’s surface, such as limestone, sandstone, bituminous coal
Metamorphic Rocks
Preexisting rock that have been altered by high temperature, high pressure, or chemically active fluids
For example: graphite, slate, or marble
Soil Terms to Know:
Soil
Soil Horizons
Soil Profile
Humus
Soil Structure
Four distinct physical parts:Mineral particles
Organic matter
Water
Air
Inhabitants include:Plants, animals, fungi, & microorganisms
Soil Horizons
Obtained by taking a core sample (soil profile)
O horizonSurface-litter layer
Rich in organic matter(dead plant material, animal waste, fungi, etc.)
A horizonTop-soil layer
Porous mixture of humus
Soil Horizons---cont.B horizon
SubsoilZone of illuviation or accumulation (area where minerals leached out of topsoil & surface litter)Typically rich in Fe and Al
C horizonContains weathered pieces of rockBelow the extent of most roots & is often saturated with groundwaterLies on top of unweathered bedrock
Soil Texture
Determined by the amounts of different sizes and types of mineral particles (clay, silt, & sand)
Loams have roughly equal portions of clay, silt, sand, & humus and is best for growing crops.
Texture, porosity, permeability determine water-holding capacity, aeration, and workability
Soil Texture—cont.
Soil porosity: measure of the spaces per volume of soil & average distances between those spaces.
As particle size increases porosity decreases, holds less water and nutrients
Soil permeability: rate at which water & air move from upper to lower soil layers
As particle size increases permeability increases, infiltration increases
Properties of Soils with Different Textures
Soil Texture
Nutrient-Holding Capacity
Water Infiltra-tion Capacity
Water-Holding Capacity
Aeration Worka-bility
Clay Good Poor Good Poor Poor
Silt Medium Medium Medium Medium Medium
Sand Poor Good Poor Good Good
Loam Medium Medium Medium Medium Medium
Soil Acidity and Plant Growth
pH of soil influences ability of plants to take in soil nutrients
H+ bind to negative sites in the soil which allows cation plant nutrients to move through the soil
Acid deposition can result in loss of soil fertility
Soil Tests
Chemical tests: pH, Salinity, Ion exchange capacity
Physical tests: water-holding capacity, percolation rate/permeability, soil texture to determine soil type
SOIL TEXTURAL TRIANGLE
PERCENTAGE OF CLAY
Read Numbers on This Side
Read Numbers on This Side
PERCENTAGE OF SILT
Read Numbers on This Side
PERCENTAGE OF SAND
How much clay, silt and sand are in the soils indicated by stars below?
Erosion
Movement of soil from one place to another
Most is caused by moving water
Types of water erosion:Sheet—wide sheet of water moves
Rill—water forms small channels
Gully—small channels join together & get wider
Water Erosion
Desertification
Conversion & loss of marginal semi-arid or arid land to desertCauses:
OvergrazingDeforestation with no reforestationSurface mining with no reclamation\Eroding/salt-concentrating (salinization) irrigation techniquesBad farming practicesSoil compaction Poisoning of soils by pesticides/chemicals
Soil Conservation & Regeneration
Conservation tillageResidues from previous crops are left in soilResidues cover & help hold soil in place
No tillageLeaves the soil undisturbed prior to planting, special machines cut a narrow furrow in the soil for seeds Increases organic material in soils & improve water-holding capacity
Preserving Soil Fertility
Two main types of fertilizer:Organic—from natural materials, complex, slow-acting, long-lasting
Inorganic—from manufactured chemical compounds• Adv: easy to get, soluble, immediately available to plants,
increases soil fertility and speeds up growing process
• Disadv: short-lived, doesn’t provide micronutrients, lacks organic material which decreases water-holding capacity, over-application impacts plants, water, and human health
Organic Fertilizers
Animal manure
Green manure: fresh or growing vegetation plowed into the soil
Compost
Spores of mushrooms, puffballs, and truffles: attach to plant roots and help absorb moisture & nutrients
Other Options for improving Soil
Adding different soils to adjust water-holding capacity
Apply lime for acidic soil
Apply sulfur for alkaline soil
Burn crop residue to add potassium
Plant legumes or apply manure to increase nitrogen
Humus: nutrients, water-holding capacity, aeration, helps root growth