EGS Frank Week 2 Soils Flashcards
Overview
- Soil Types are very much a () of the prevailing ()
- In Humid Tropics, soils are () & thus very ()
- In Arid regions, soils are () or () given the ()
- Soils types are very much a function of the prevailing rainfall conditions.
- In Humid Tropics, soils are deeply weathered and thus very deep
- In Arid regions, soils are very thin or absent given the limited rainfall
Overview
- () plays a crucial role in soil formation.
- Hot & Wet areas promote () & soils ().
- Less wet areas promote () & () soils.
- Leaching by water plays a crucial role in soil formation
- Hot & Wet areas promote much chemical alteration & soils rich in Iron Oxides
- Less wet areas promote moderate leaching & less mature soils.
Overview
- Dryland Soils accumulate () such as () & () as there is (), and are not () when compared to the ().
- Dryland Soils are also () & thus are lacking (), and prone to () via () & ()
- Aridsols are () and may be () or ()
- Dryland Soils accumulate evaporation products such as salts & calcium as there is little leaching, and are not very evolved when compared to the underlying geology.
- Dryland Soils are also bare & thus lacking in organic content and prone to erosion via wind & water.
- Aridsols are very thin and may be alkaline or salty
Overview
- Desert Margins promote the formation of () which support () , & thus also have a ().
- () are the most leached & deeply () and home to (), hence the () colour, but have very low ().
- They are also () and form () called () or ().
- Desert Margins promote the formation of Mollisols which support grasslands, & thus also have a higher organic content.
- Tropical Oxisols are the most leached & deeply weathered and home to iron, hence the reddish colour, but have very low organic content.
- They are also acidic and form iron crusts called laterites or ferricretes.
Overview
- Alfisols and Ultisols are less (), more () and accumulate (), and can be ().
- Thus rainfall does not only () but is also responsible for ().
- The best soils for agriculture are those ()
- Alfisols and Ultisols are less leached, more moderate and accumulate some clays and nutrients, and can be productive.
- Thus rainfall does not only provide moisture but is also responsible for soil formation.
- The best soils for agriculture are those in moderate settings.
Definition
Leaching Definition:
2 points
- The loss of soluble substances & colloids from the top layer of soil by perlocating precipitation
- The materials lossed are carried downwards & are generally redeposited in a lower layer
What are some of the Major Soil Types in the Tropics & Subtropics?
6 points
- Aridsols
- Mollisols
- Oxisols
- Alfisols
- Ultisols
- Vertisols
What climates are these soils roughly located?
- Aridsols -
- Mollisols -
- Oxisols -
- Alfisols -
- Ultisols
- Vertisols -
- Aridsols - Deserts
- Mollisols - Grasslands
- Oxisols - Tropical
- Alfisols - Humid/warm climates
- Ultisols - Subtropical w. exposure to a brief dry season
- Vertisols - Semi-arid tropical regions, but also might be azonal
Area (km2) of the soil types
- Aridsols -
- Mollisols -
- Oxisols -
- Alfisols -
- Ultisols -
- Vertisols -
- Aridsols - 15 Ma km2
- Mollisols - 9 Ma km2
- Oxisols - 9.8 Ma km2
- Alfisols - 12 Ma km2
- Ultisols - 11 Ma km2
- Vertisols - 3 Ma km2
Location of these soils P1/6
(1) Aridsols
5 points
- USA
- Middle East
- Africa
- Australia
- South America
Location of these soils P2/6
(2) Mollisols
3 w. add points
- North America - Great Plains (3 Ma km2)
- Asia - Central Asian Steppers (2.5 Ma km2)
- Australia
Location of these soils P3/6
(3) Oxisols
2 points
- Africa
- South America
Location of these soils P4/6
(4) Alfisols
4 points
- Europe
- Africa
- USA
- Australia
Location of these soils P5/6
(5) Ultisols
5 points
- SE Asia
- Africa
- North America
- India
- Australia
Location of these soils P6/6
(6) Vertisols
3 points
- Sudan
- India
- Australia
Desert Soils - Aridols Charactersitics
(1) Aridsols
- Weathering:
- Organic Content:
- Leaching:
- Horizons:
- Minerals:
- pH:
- Erosion:
- Add Notes #:
1. Weathering:
* Thin, unweathered
* More mature in semi-arid/savannas
* similar to geology
2. Organic Content:
* Lack of organic material & nutrients
3. Leaching:
* Lack of leaching
4. Horizons:
* poorly developed horizons
5. Minerals:
* Build-up of evaporates
* Calcium & salt (salty layer possible)
6. pH:
* Alkaline mineral soils
7. Erosion:
* Wind & Water
8. Add. Notes: -
Grassland Soils - Mollisols Characteristics
(2) Mollisols:
- Weathering:
- Organic Content:
- Leaching #:
- Horizons #:
- Minerals:
- pH #:
- Erosion:
- Add Notes #:
1. Weathering:
* Mature, well-drained
2. Organic Content:
* High organic content from plant root decay
* Nutrient-rich, fertile
3. Leaching:
* Less prone to leaching due to high organic content
* & bc in grasslands often evapotransp. > or ⇌ (balances) precip.
4. Horizons:
* Thick, dark surface horizon (mollic epipedon)
5. Minerals:
* Calcified
6. pH:
* Neutral to slightly alkaline
7. Erosion:
* Wind (e.g. Dust Bowel)
8. Add Notes: -
Tropical Soils - Oxisols Characteristics
(3) Oxisols:
- Weathering:
- Organic Content:
- Leaching:
- Horizons:
- Minerals:
- pH:
- Erosion #:
- Add Notes #:
1. Weathering:
* Highly Weathered
2. Organic Content:
* Lack organic layer
* Xtremely low fertilility
3. Leaching:
* Significant leaching
4. Horizons:
* Deep oxic subsurface horizon
* Horizon boundaries generally arbitary
5. Minerals:
* Red due to Iron & Aluminium
* Acidic soils w. kaolinitic clays
* Laterisation (iron crusts) if oxic horizon exposed to air
6. pH:
* Acidic
7. Erosion:
* Minimal w. intact veg.
* Improper land use = severe erosion
8. Add Notes #:
* Deep, thick soils
* Formed under tropical rainforest veg
* Found on gentle slopes
Humid/Warm Climate Soils - Alfisols Characteristics
(4) Alfisols:
1. Weathering:
2. Organic Content:
3. Leaching:
4. Horizons:
5. Minerals #:
6. pH:
7. Erosion #:
8. Add Notes #:
1. Weathering:
* Moderate weathering
2. Organic Content:
* Organic rich & high fertility
3. Leaching:
* Moderate Leaching
4. Horizons:
* Clay, subsurface horizons
* Well-developed & contrasting
5. Minerals:
* Retain signific. amount compared to Oxisols
* Typically calcium carbonate depleted
6. pH:
* Slightly acidic
7. Erosion : -
8. Add Notes : -
Subtropical Soils - Ultisols characteristics
(5) Ultisols:
- Weathering:
- Organic Content:
- Leaching:
- Horizons:
- Minerals #:
- pH:
- Erosion #:
- Add Notes:
1. Weathering:
* relatively highly weathered soils
2. Organic Content:
* Relatively low native fertility
* Potential to be productive w. inputs
3. Leaching:
* Relatively significant leaching
4. Horizons:
* Subsurface horizon of clay & iron
5. Minerals:
* limited primary & nutrient minerals w. abundant secondary minerals
6. pH:
* Acidic
7. Erosion:
* Can be prone to signific. erosion?
8. Add Notes:
*Exposed to brief dry season
Semi-arid tropical/ swelling soils - Vertisols Characteristics
(6) Vertisols:
- Weathering #:
- Organic Content #:
- Leaching #:
- Horizons #:
- Minerals :
- pH #:
- Erosion #:
- Add Notes:
1. Weathering: -
2. Organic Content:
* moderate?
3. Leaching:
* limited?
4. Horizons:
* shrink/swell action generally prevents formation of dististinct, well-developed horizon
5. Minerals:
* Parent rock rich in (swelling) clay minerals
6. pH:
7. Erosion:
* Low to moderate bc high clay content & swelling props. hinder erosion
8. Add Notes:
* Marked seasonal rainfall
* Moisture -> Swelling/expansion
* Dry Cycle -> shrink & deep cracks
P1/4
What are the connections between atmospheric circulation, rainfall patterns and soil type?
- Driven by the (), atmospheric circulation patterns, such as the () and the () such as the () cell, () cell, and () cell, influence the () spatially & temporally, and thus the () across the globe.
- For example, the presence of the () and the () in the Tropics and the Subtropics:
() air () and results in () near/along the equator & the air then () near the () resulting ().
- Driven by the differential heating of the Earth’s surface, atmospheric circulation patterns, such as the Intertropical Convergence Zone (ITCZ), and Global Circulation patterns such as the Hadley Cell, Ferrell Cell, and the Polar Cell, influence the divergence & convergence of air masses spatially & temporally, and thus the distribution of rainfall across the globe.
- For example, the presence of the ITCZ and the Hadley Cell in the Tropics & the Subtropics:
Warm, moist air rises and results in frequent, high rainfall near/along the equator & the air then cools & sinks near the subtropics resulting in high pressure conditions (dry, low rainfall.
P2/4
What are the connections between atmospheric circulation, rainfall patterns and soil type?
- The () & () of rainfall affects soil () and soil ().
- For example, regions near the Equator receive () rainfall which results in () -> formation of () soils w. (), such as ().
- The distribution & intensity of rainfall affects soil moisture levels and soil formation processess.
- For example, regions near the Equator receive high, frequent rainfall which results in intense leaching -> formation of deeply weathered soils w. low nutrient content, such as Oxisols.
P3/4
What are the connections between atmospheric circulation, rainfall patterns and soil type?
- Whilst regions in the Subtropics with arid conditions receive () rainfall which results in () leaching -> formation of (), () and more () soils that accumulate (), such as ().
- Whilst regions in the Subtropics with arid conditions receive limited/low rainfall which results in limited leaching -> formation of poorly weathered/ unweathered, thin and more alkaline soils that accumulate salts & calcium such as Aridsols.
P4/4
What are the connections between atmospheric circulation, rainfall patterns and soil type?
- In regions w. more moderate rainfall such as (), there is less () & () and thus these soils tend to have more () as these conditions lend themselves to () and thus a more (), such as () & ()
- In regions w. more moderate rainfall such as the temperate climates, there is less leaching & weathering and thus these soils tend to have more nutrients & clays as these conditions lend themselves to high fertility and thus a more stable nutrient cycle, such as Alfisols & Ultisols.
