the forming soil Flashcards
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
hydrolysis
leaching
chelation
gleying
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
pyroxenes
olivines
amphiboles
what are the more resistant primary minerals that also make up sedimentary rocks
feldspars
micas
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
