Weathering and soil formation

1. Weathering and soil formation Geomorphology 2010 38/42:278

3. Geodynamic Processes Pedogenesis (soil formation) and Morphogenesis (structural)development do not happen in a cycle pattern, but rather simultaneously causing them to interfere with each other. Distinguishing between the processes makes it possible to identify one of the three types of geodynamic environments. -Stable -Intermediate -Unstable

4. Geodynamic Processes Stable environment: -slow evolution with a steady state of formation -regions of low intensity of geomorphic activity and processes -Favourable conditions for soil formation 2 forms exist: -Long term stability with surface evolution little to none -Almost recent stability remnant forms due to quaternary oscillations

5. Geodynamic Processes Intermediate Environment: -Pedo. And Morph. Interfere each other with one weakly favoured more. Unstable Environment: -Morphogenesis dominates over pedogenesis -Formation can not balance, land becomes marginal

6. Pedogenesis 3 main models of soil formation: -normal �top-down� development -development accompanied by pedoturbation -altering with sediment deposition

7. Soil Chronosequences -soils continue to evolve during time, or if they reach equilibrium? - Its the concept in which a succession of formations (moraines...etc.) of progressively greater age but with similar factors are shown to have soil profiles with progressively greater development. -Long term patterns see decreasing rates of soil development

8. Soil Chronosequences 3 processes that take place: 1. Addition- of materials and minerals 2.Transformation- of minerals and silicates to stable hydrous oxides 3.Transfer- of soil components to greater depths

9. Mineral Deposition 3 main groups: 1.Calcretes 2. Silcretes 3. Ferricretes

10. Calcrete -formed by carbonates -mostly Mg, K, Na, Ca -Chronosequences of secondary mineral accumulation -Formation is common -Shallow accumulation of carbonate -May effectively control scarp formation -mostly semi-arid areas( Pg. 48)

11. Calcrete -Series of 6 formation stages Stage: Preparation of host material Soil formation and horizon differentiation Accumulation of calcium carbonate Profile development Induration reworking

12. Calcrete

13. Ferricrete -rock formed from lateritic crust -water plays major role -leaching of aluminum and iron hydroxides -oxidization is irreversible -also called �soil armor� -strong structural control of landscape -reddish -humid conditions

14. Ferricrete

15. Silcretes -silica replaced existing soil -hot arid climate -Caused by water logging -cements soil grains -less developed -physiochemical process

16. Silcretes

17. Formation Through Time Soil formation undergo three processes: 1. Rock decomposition and alteration 2. increase with the amount of organic matter 3. transport of soluble colloid elements through the profile

18. What are Soils Formed From? There are 2 groups of inorganic parent material: - Sedentary (Formed in Place) -Transported Sedentary parent material is called �Residuial� because it is still at the original site. The transported group is broken down further by the types of transportation and deposition.

19. What are Soils Formed From? The different transported parent materials: By Gravity: 1. Colluvial By Water: 2. Alluvial (streams) 3. Marine (oceans) 4. Lacustrine (lakes) By Ice: 5. Glacial By Wind: 6. Eolian

20. The processes of breaking down the parent material allowing it to be transported: Physical Weathering: -crystal growth -Thermal expansion and contraction -pressure release and unloading -biological Chemical Weathering: -oxidation -hydrolysis -hydration

21. Paleosols -soils of a past environment -identified by land surface altering due to insitu processes -fossilized soils -used to date soils to a period of time -determines climate and topographic conditions -Either �buried� or �relict�

22. Relict Vs. Buried Relict -formed on pre-existing landscapes -never buried -polygenetic Buried -under sediments -pedogenesis can not exist