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Flashcards in the forming soil Deck (25)
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what are the five soil forming factors

climate (cl)
biological activity (o)
relief (r)
parent material (p)
time (t)


describe zonal soils

adequate time for formation
normal relief landscapes (flattish)
ordinary silicious parent materials (often sedimentary rock)
distinguishing features due to climate and associated vegetation


describe intra zonal soils

soils developed on different parent material or have special effects induced by fluctuating water table or topography


describe azonal soils

soils that have not had sufficient time to mature due to geological processes such as fooding or avalanches which result in the dumping o new parent materials for example the rangetiki soils


what are biosequences

they are formations due the different types of vegetation growing on them ie eg cup podzols


what are toposequences

soil associations that have formed in response to changes in relief


what is physical weathering and how does it lead to chemical weathering

its the breakdown of material into smaller material = increase SA = increased reactivity = chemical weathering


an example of physical weathering

mechanical abrasion due to rivers having strong flows or flooding to the deposition of alluvium and creation of degradation terraces


what is translocation

the redistribution of dissolved minerals or dissolved particles through porous rock or soil very important in podzol formation
eluviation = removal (e horizon)
illuviation = deposition (B horizion)


what are 4 different chemical weathering processes



what is hydrolysis

the reaction between hydrogen and hydroxide ions dissovled in water with the chemical elemnts in the mineral lattice within rocks . H+ ions are exchange with cations within the rock and diffused into the soil these cations are then either taken up by plants roots or lost n the soil via leaching in order for hydrolysis to continue these cations must be removed to prevent equilibrium


what increases hydrolysis (3)

- low ph as there are more h+ ions to replace cations
- fine textured soils due to increased SA thus increased reactivity
- higher temps as particles have more energy so reactions are more likely to take place


what is leaching

the downward or lateral movement of cations released during hydrolysis


what can impact leaching rates

can be increased with increased rainfall
can be decreased if lots of vegetation is present due to the roots taking up the cation ions faster than the leaching process can occur


how does leaching effect hydrolysis

leaching allows the hydrolysis process to continue as it prevents equilibrium
its is also a cycle Increased leaching = increased soluble cations lost = increased acidity = increased hydrolysis


what is chelation

chelating agents produced by alterations of humus by plant acids or excreted by lichens bind with cations in rock which make them more easily removed during the hydrolysis process


what is gleying

it is when the soils are a blue - grey colour due to a high perched water table meaning they are predominately staurated this removes the oxygen and denitrification can take place


3 main classifications of nz parent materials

Igneous rock
sedimentary rocks
metamorphic rocks


what are igneous rocks

formed from the cooling of molten magma they are a source of primary minerals


what are sedimentary rocks

formed from the burial and compaction of weathering products and resistant primary minerals glued together by secondary minerals such as clay and oxides


what are metamorphic rock

deeper burial compaction and heating of sedimentary rocks new materials are formed due to the formation process


what are the least resistant primary minerals



what are the more resistant primary minerals that also make up sedimentary rocks


and quartz is the most resistant


Describe aggradation and provide an example off its occurrence in the Manawatu

Aggradation is the process of alluvium accumulating and building up landscapes due to cold periods in the climate cycle. These are the older terraces we see around the area for example the ohakine terraces which is the most recent aggradation terrace. There is a lack of vegetation thus more erosions taking place and being deposited in rivers which due to the cold temperatures are often not flowing as fast or strongly and accordingly cannot get rid of the accumulating eroded material, so it accumulates on the landscapes instead. Winds also plays a large role as material is carried by the strong forces and deposited on the landscapes also (losses).


Describe degradation and provide an example off its occurrence in the Manawatu

Degradation is the cutting into landscapes and formation of degradation terraces, the most recent in Manawatu being the rangitikei soils. This happens when the climate is warming during the global climate cycle, ice has melted and accordingly the rivers are flowing quicker and stronger. Warmer climates means vegetation is growing again and thus erosion is less so the rivers are able to remove the material sufficiently. However, the strong rivers begin cutting in to the landscapes due to the erosion being removed faster than its coming in thus the establishment of these degradational terraces