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Quick review for G107 Physical Geography Part III

Draft

Part III

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Soil ‘And the Lord God formed man (woman) of dust (soil)

from the ground..and out of the ground the Lord God formed every beast..bird’

Soil: definitions… depends on the fieldSoil is the upper layer(s) of the earth in

which fine rock particles and organic material provide the basis for plant life (inorganic + organic + living things)

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Why different Soils Five major environmental factors in soil

formation S = f(CROP)T

S = soil F = function C = climate R = relief (topography) O = organism (plants & animals) P = parent materials

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Soil profileLayers/colors in soil = soil profilePedon = 3-D representation of soil

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Soil Horizons

Soil Profile Divided into three zones or horizons

O- accumulation of decaying matter (included in A horizon)

A- zone of Eluviations B- zone of Illuviation C- transition zone between solum or true soil and parent

material

Solum or true soil is made up of A & B horizons

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Soil Properties Color – black, gray, brown, yellow, blue, green, red, white

Black indicates the presence of organic (humic) matter i.e. fertile soil

Red indicates the presence of iron compounds

Texture Size of individual grains: gravel, sand, silt and clay (gravel is not considered here) loamy soil, silty clay,

clayey sand

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Soil PropertiesStructure

Crumpy, granular, blocky, columnar, prismatic, and platy

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Soil PropertiesChemistry

pH, Base ions (base cations) Ca, Mg, K, Na- clay minerals- illite, kaolinite,

montmorillonite

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Pedogenic RegimesLaterization (ferralitization)PodzolizationGleizationCalcificationSalinization

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Soil Classification Soil Orders

Oxisols – heavy leaching… equatorial/tropics Ultosols- clay accumulation… equatorial/tropics Vertisols.. Tropics/subtropics Alfisols.. Accumulation of clay… subhumids Spodosols- cold moist climates Mollisols- subhumid- semiarid..chernozem..prairie Aridisols- dry climates Histosols- large accumulation of organic… bog soil Entisols- lack soil horizon Inceptisols- some weakly developed soil horizon

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The Earth Divided into three major layers Crust- continental crust (Sial)(lighter than

oceanic crust) and Oceanic (Sima) crust with Crust plus upper mantle = lithosphere Boundary between crust and mantle =

Mohorovicic Discontinuity (MOHO) Mantle

Lower (plastic) part of upper mantle = Asthenosphere

Core

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Plate Tectonic Lithosphere = crust and upper mantle Asthenosphere = the semi-liquid part of upper

mantle Lithosphere broken into large pieces called

PLATES Three types of plate boundaries

Divergent Convergent Transform

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Composition of the CrustEight elements (oxygen (47%), silicon

(28%) aluminum, iron, calcium, sodium, potassium and magnesium) form the bulk of the minerals in the crust.

There are over 3000 known minerals A mineral is a natural occurring substance

that is inorganic, has definite chemical composition, and is crystalline

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Group of Minerals Silicate- most important group- examples

Quartz, feldspar (orthoclase, plagioclase), Mica (Biotite & Muscovite), amphibole, pyroxene, olivine

Carbonate- calcite Sulfides- galena & pyrite Sulfates- gypsum Oxides- hematite Phosphate- apatite Halides- halite Natives- sulfur, copper, silver, gold

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Mineral Physical characteristic Color Streak Luster Hardness Crystalline form Fracture Cleavage Others- striations, smell, odor etc.

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RocksRocks are aggregation of minerals,

usually made of two or more minerals.

Three Rock Groups Igneous Metamorphic Sedimentary

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Igneous Rocks Igneous rocks are rocks that form from

molten material = magma The molten rock is magma when it is still

within the earth and Lava when it exposed on the earth’s surface

Intrusive and extrusive Can tell them apart using Texture (Phaneritic

(visible with naked eye) and Aphanitic)

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Igneous Rocks Contd.

Examples of Intrusive igneous rocks Granite, Diorite, Gabbro, Pegmatite

Examples of Extrusive Igneous Rocks Rhyolite, Andesite, Basalt, Obsidian,

Pumice Scoria

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Plutonic Rocks Intrusive igneous rocks classified based

on size, depth of formation and relationship to surrounding rocks

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Metamorphic Rocks These are rocks that form as a result of

alteration of existing rock due to high temperature and or pressure

Two types of Metamorphic Rocks Non foliated and Foliated Nonfoliated metamorphic rocks include

quartzite, marble, anthracite coal Foliation is the alignment of minerals

Examples of foliated met. Rocks- slate, schist, phyllite, gneiss

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Sedimentary Rocks Produced from broken pieces of rocks or

precipitates or Lithification id the process whereby individual

sediments are turned into solid rocks Types of sedimentary rocks- clastic (detrital)

& biochemical Examples of sedimentary rocks- sandstone,

conglomerate, breccia, siltstone, mudstone, shale, limestone, rock salt, bituminous coal

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Weathering and Mass WastingWeathering is the breakdown of rock or

chemical decomposition of rock, thus two types of weathering: Physical (Mechanical) and Chemical

PhysicalChemical

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Physical weatheringFrost actionSalt actionUnloadingPlantsAnimalsHeating & Cooling cycles (thermal)

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Chemical weatheringOther than the rock itself, water is the

most important substance needed for chemical weathering

HydrationHydrolysiscarbonicSolution

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Mass Wasting The downward movement of earth material under the

influence of gravity Classified based on material type, velocity, water

content Types of Mass Wasting

Fall…

Flow……just like a river

Slump…this is what kids do in the park …remaining intact as shown in the diagram

Slide…rolling (turn over) … Creep- this occurs imperceptibly

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Expanded Key Words & Phrases

Soil horizons, base cations, leaching, eluviations, Illuviation, soil colors and their meaning, pedogenic regimes or soil forming processes, minerals, rocks, plate boundaries, chemical weathering, mechanical weathering, karst terrain, plate tectonic, lithosphere, Sial (Continental crust) & Sima (Oceanic crust) with Sial being denser than sima, asthenosphere, Mohorovicic Dicontinuity (MOHO) the boundary between crust and mantle, Weathering (Physical (mechanical) & Chemical), climates favorable to physical weathering and chemical weathering, mass wasting…types and being able to identify them given drawing