Soil & Soil Dynamics. Rock cycle- the constant formation and destruction of rock. The Rock cycle is...
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Transcript of Soil & Soil Dynamics. Rock cycle- the constant formation and destruction of rock. The Rock cycle is...
Rock cycle- the constant formation and destruction of rock. The Rock cycle is the slowest of all cycles.
The Rock Cycle
Igneous rocks- rocks that form directly from magma.
Intrusive igneous- form from within Earth as magma cools.
Extrusive igneous- from when magma cools above Earth. (ex. A volcano that ejects magma out will form this)
Classified by chemical composition Basaltic rock – dark colored rock that contains minerals
with high concentrations of iron, magnesium and calcium Granitic rock – lighter colored rock made up of the mineral
feldspar, mica and quarts.
The Rock Cycle
Sedimentary rocks- form when sediment such as mud, sands, or gravels are compressed by overlying sediments. Sedimentary rocks are classified by their
chemicalmakeup and properties. Types of sedimentary rock
Clastic – formed when rocks have been carried to a different spot, weathered, and through pressure from overriding rock take a different form.
Shale – made mostly of clay.
The Rock Cycle
Metamorphic rocks- form when sedimentary, igneous or other metamorphic rocks are subjected to high temperatures and pressures.
Three main forces responsible for the transformation of different rock types to metamorphic rock are; Internal heat from the Earth The weight of overlaying rock Horizontal pressures from previously changed rock.
The Rock Cycle
Weathering- when rocks are exposed to air, water, certain chemicals or biological agents that degrade the rock.
Physical weathering- the mechanical breakdown of rocks and minerals.
Weathering and Erosion
Chemical weathering- the breakdown of rocks and minerals by chemical reactions.
It takes place in one of the following waysOxidation – reaction with O2
Hydrolysis – reaction with H2OAcid action – reaction with acid substances (H2CO3, H2CO4, H2SO3)
H2CO3 – carbonic acid is the most important natural acid
Weathering and Erosion
Erosion- the physical removal of rock fragments from a landscape or ecosystem.
Erosion converts soil into sediment. Wind, water, ice transport and living
organisms can erode materials. Deposition- the accumulation or depositing
of eroded material such as sediment, rock fragments or soil.
Erosion
Soil is important because it Is a medium for plant growthServes as a filter for waterA habitat for living organismsServes as a filter for pollutants
Soil
Factors that determine the formation of soil: Parent material- what the soil is made from influences soil formation
Climate- what type of climate influences soil formation
Topography- the surface and slope can influence soil formation
Organisms- plants and animals can have an effect on soil formation
Time- the amount of time a soil has spent developing can determine soil properties.
The Formation of Soil
O horizon- (organic layer) composed of the leaves, needles, twigs and animal bodies on the surface.
A horizon- (topsoil) the zone of organic material and minerals mixed together.
B horizon- (subsoil) composed primarily of mineral material with very little organic matter
C horizon- (parent material) the least weathered horizon and is similar to the parent material.
Soil Horizons
Chemical Properties of Chemical Properties of SoilSoil
Cation exchange capacity- the ability of a soil to adsorb and release cations, positively charged mineral ions.
Soil bases- calcium, magnesium, potassium and sodium
Soil Acids- aluminum and hydrogen
Base saturation- the proportion of soil bases to soil acids
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Biological Properties Biological Properties of Soilof Soil
Many organisms are found in the soil including fungi, bacteria, protozoans, rodents and earthworms.
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Soil ConservationSoil Conservation Topsoil is the nutrient-rich soil layer, millimeters to
meters deep, that contains a mixture of organic material and minerals. It is a renewable resource if properly maintained.
Billions of acres of land worldwide are bare due to erosion, nutrient depletion, overtillage, and misuse.
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