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Ag Science > Soil Formation > Flashcards

Soil Formation Flashcards

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1
Q

Factors affecting soil formation

A
  • Parent Material
    -Topography
    -Time ( Takes time for rocks & OM to breakdown & soils to develop)
  • Climate
  • Living Organisms ( Decomposers in soil breakdown OM to provide nutrients to soil)
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2
Q

Soil Provides…
Soils Functions?

A
  • A medium in which crops can be grown
  • physical support for plants
  • A medium in which plant and animal remain can be decomposed, allowing for nutrient recycling.
  • Soil also allows for the retention and provision of water&air for crop growth
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3
Q

Parent Material

A
  • The type of rock in which soils are formed from.
  • Has an impact on acidity and texture of soil formed from it.
  • Limestone is alkaline = alkaline soils,
    Sandstone is acidic = acidic soils.
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4
Q

3 groups to classify rocks

A
  • Igneous
    -Sedimentary
  • Metamorphic
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5
Q

Igneous Rocks

A
  • Formed when magma cools and hardens
  • If magma cools slowly = large crystals
  • If magma cools quickly = small crystals
    EG of crystals = quartz/mica
    Example of igneous rocks = Granite (Donegal), Basalt (Antrim)
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6
Q

Sedimentary Rocks

A
  • Sediment is deposited on seabed/lakebeds and layers begin to form. Over long periods of time (100s of years), pressure is put on the lower layers and the sediment becomes compressed into rocks.
    EG: Limestone (fossils and shells) Burren Co. Clare
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7
Q

Metamorphic Rocks

A

Form when other rocks (igneous & sedimentary) are placed under a great heat/pressure. Changes rock into new rock.
EG; Marble from limestone
Quartzite from sandstone

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8
Q

mechanical weathering

A

The physical breakdown of large particles into smaller particles.
Heating and cooling
Freeze-thaw action
Abrasion
Roots
Animals

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9
Q

Chemical weathering

A

The chemical breakdown of large particles to smaller particles
Oxidation
Solution/Carbonation
Hydrolysis

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10
Q

Oxidation

A

Minerals react with O2 and H2O. The oxidation of iron gives a rust colour to rocks

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11
Q

Solution/Carbonation

A

As rain falls CO2 from the air dissolves it in forming a weak carbonic acid. This acidic rain reacts with the rock and wears it away

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12
Q

Hydrolysis

A

Rocks are broken down when substances react with water

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13
Q

Heating & Cooling

A

Heating causes an expansion of material and cooling causes contraction, as the minerals in rocks heat and cool they expand and contract at different rates causing them to shatter.

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14
Q

Freeze-Thaw Action

A

Water expands as it freezes,
When it rains the water collects in cracks in the rock and when the temperature droops the water freezes and expands putting pressure on the rock.
When the water thaws this pressure is released.
As this repeatedly occurs, the build up of pressure and release on the rock causes it to shatter.

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15
Q

Abrasion

A

As rocks move around (by, gravity, wind or water) they hit off each other, this causes them to be worn down

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16
Q

Roots

A

Roots can enter cracks in rocks and as they grow they put pressure on the rocks contributing to the rocks prying apart

17
Q

Animals

A

Burrowing animals can cause rocks to breakdown when they dig for food or shelter

18
Q

Climates impact on soil formation

A

Temp. and rainfall contribute to both MW and CW of rocks.
They also influence the rate of reactions in soils and the proportions of water and air in the soil

19
Q

Topography impact on soil formation

A

Topography is the mapping/shaping of te surface of the land.
Soils that develop on slopes tend to be shallow as the soil moves down with gravity resulting in deep soil in the valley.

20
Q

Soil Profile & Layers

A

5 Layers
O - Made up of OM

A - Topsoil. Organic matter and minerals from parent material

B - Subsoil. Rich in minerals that have leached through O & A horizons

C - Parent Material. Mostly consists of parent material from which the soil has developed.

R - Bedrock. Mass of parent material, not soil

21
Q

Brown Earths

A

Does not have distinct horizons, uniform in colour throughout.
- Found overlying limestone
- Has a high pH
- Dark brown in colour throughout
- Little leaching takes place, very fertile soil
- Requires little fertiliser
- Good drainage
USED for crop production, very versatile

22
Q

Podzol

A

Soil profile : O horizon, A1 & A2 (horizon due to acid leaching ‘podzolisation’ ), B2 ( minerals accumulate here, red brown in colour) , Iron Pan, Bedrock

  • Found overlying acidic parent material, e.g Sandstone
    -One of the most acidic soils in IRE
  • Used for forestry/ rough grazing
  • Prone to leaching minerals
  • Podzolisation occurs = iron pan
  • Accumulate in the B horizon, forming an iron pan that is impermeable to water and can cause water logging.
23
Q

Podzolisation

A

Occurs in acidic pH conditions where minerals such as Fe and Al are leached from the A horizon, leaving it bleached in colour. They accumulate in the b horizon, forming an iron pan that is impermeable to water.

24
Q

Gley Soils

A

Formation of a grey occur sin waterlogged conditions and is known as gleisation.
- Formed in areas after a rainfall.
- Promote anaerobic conditions due to their high-water levels.
- Waterlogged conditions causes the oxidation of Fe to occur leading to mottling, resulting in blue and grey colours in horizon B
- Poor drainage and structure
- Rushes are often present as weeds & artificial drainage is sometimes needed to reduce water-logging.
- Used for extensive grassland for animal production

25
Q

Gleisation

A

is the formation of grey in waterlogged conditions when the water logging causes the oxidation and reduction of minerals leading to mottled appearance.

26
Q

Peats/Bogs

A
  • Peat is the main material that is produced from plant remains when oxygen is not present
  • Peat is rich in organic matter
  • The anaerobic conditions only allow for partial breakdown of the OM by microorganisms. If these layers of partially decomposed material build up, they form a peat.
  • An area where peat accumulates is called a bog.
  • If the build-up occurs in a lake, a basin bog is formed. If deposition continues above the level of the lake, a raised bog is formed.
  • If the build-up occurs on a flat or sloped landscape, a blanket bog is formed.
    KNOW DIAGRAM
27
Q

Blanket bog

A

Develop in areas of high rainfall and low evaporation in anaerobic conditions. Found in mountainous areas.

28
Q

Weathering

A

Decomposition of rock without changing its location

29
Q

Erosion

A

Breakdown of rock particles by wind, water or ice

30
Q

Raised bog

A

Formed when materials accumulates on top of a basin peat

31
Q

Eluviation

A

The transport of soil particles or minerals from the upper layers of a soil to the lower layers of a soil by precipitation of water

Ag Science (12 decks)

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