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28 Cards in this Set
- Front
- Back
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Pyroxenes and feldspars are altered by chmical weathering to |
Haematite and Kaolinite |
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What weathering processes occurnin the submarine environment? |
Low temperature alteration of volcanic rock and deep sea sediment by seawater High temperature interaction of seawater and newly formed oceanic crust at Mid Ocean Ridges |
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Frost wedging |
Water freezes in cracks, expands by 9% Large angular blocks produced Might also cause granular disintegration of coarse grained rock like granite |
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Thermal weathering |
Yemperature changes cause expansion and contraction Thermal gradient setup between the inside and outside of the rock producing stress Cracks form Repetition results in widening of cracks and flaking off |
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Salt weathering |
Salt crystallises inmpores and/or fractures. Growing salt crystals generate internal pressure forcing crackmopen or cause granular disintegration |
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Wetting and drying |
Poorly cemented rock such as shale is disintegrated by alternating wetting and dryingm most disintegration occuring in the drying cycle. |
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Pressure release |
Release of confinging pressure due to erosion of overlying rocks causes tensile stresses due to upward rebound of underlying rock. Fractures develop parallel to the topography. |
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Hydrolysis |
H+ formed by dissolution of Co2 in water. CO2+H2O =H2CO3=H+ + HCO3- Clays formed if aluminium is present. |
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Hydration-dehydration |
Water is added or removed to from new minerals Water + haematite = geothite- ferric oxides Gypsum- anhydrite+ water |
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Oxidation |
Oxidation of iron and manganese bearing minerals such as biotite, pyroxene or pyrite. Pyrite+oxygen = haematite |
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Solution |
Minerals such as calcite,, dolomite, gypsum and halite will dissolve when exposed to water. |
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Chelation |
Natural organic compounds foorm complxes with elements, usually metals, keeping them innsolution under pH cconditions whhere they would normally precipitate. Lichens important in chelating aluminium. |
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Processes included in halymyrolysis |
Alteration ofmone clay type to another Formation of glauconite from feldspar and mica Formation of phillipsite and palagonite from volcanic ash. |
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Halymyrolysis |
Synonym for submarine weathering |
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7 Soil forming processes |
Humification Gleization Podzolisation Lessivage Ferralization Calcification Salinization and desalinization |
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Humification |
Transformation of organic matter into soil humus and organic acids. |
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Gleization |
Reduction of iron under anoxic conditions (usually under the water table) to produce blusih grey waterlogged soil. |
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Podzolisation |
Downward migration of al, fe and/or organixc matter Results in the relative increase in concentrations of silica in upper layer Results inndestruction of clay minerals and leaching of exchangeable catiins. |
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Lessivage |
The mechanical movement of clay size mineral particles from tg A horizon to the B horizon, resultin in relative clay enrichment in the b horizon |
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Ferrallitazation |
Intense and deep weathering forming thick uniform soil profiles. These are depleted in exchangeable cations snd enriched in clay such as kaolinites as well as oxides such as gibbisite and haematite. |
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Calcification |
The accumulation of soluble salts such as sulfate and chlorides of calcium in subsurface horizon. If sufficient water is present more cations such as Na+ K+ Mg2+ may be removed byt not Ca 2+ resulting in calcium enrichment |
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Salinization and desalinization |
Accumulation of soluble salts such as sulfates and chlorides ov calcium, magnesium sodium and pottasium. Or the leaching of these salts from these horizons |
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What are some features used in recognising Paleosols |
Coal or peat horizons Root traces Gradational changes Soil strucgure Burrows Nodules and concretions |
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Paleoclimate indicators |
Marine carbonstes and reefs Glacial deposits Storm deposits Coals and lignites Fossil flora and fauna |
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Variation is solar energy received mah be due to |
Changes in latitude and continental drift Seasonal cycles Milankovitch cycles Atmospheric variaviloty |
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Effect of climate on weatheringand soil formation |
Warm humid - chemical Hot, dry - physical Intensity of weathering determines characteristics andmminerals in paleosols |
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Effect of weathering on sediment teansport |
Humid climates probide adequate water flow for stream transport. Seasonality of precipitation is also important. Wind may be important in arid climaes and in coastal areas. Cold climates may have glacial transport Storminess - strong wave activiy and currentsthat rework sediments |
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Effect of climate on Evolution and extinction of organisms |
Extinction of major groups of organisms at various times in the geological record due to climate change. |
