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FGASA Level 2 > Geology > Flashcards

Geology Flashcards

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1
Q

What are the three different major rock types

A

Metamorphic
Sedimentary
Igneous

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2
Q

What is the rock cycle ?

A

The earths crust, atmosphere and hydrosphere are involved in a constant cycle known as as the rock cycle
Driven by plate tectonics and involves the reconstruction of rock forming compounds in response to changing environmental conditions specifically temperature, pressure, water and the atmosphere

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3
Q

Explain the 4 different stages of the rock cycle

A

Stage 1: formation of igneous rock
when molten magma cools forming ingenuous intrusive rocks(granite) formed below the earths surface between other older rocks or igneous extrusive(basalts) rocks that form as a result of volcanic eruptions

Stage 2: formation of sedimentary rock
-Takes place when igneous rocks get exposed to various processes at earths surface( weathering, erosion, transportation and deposition)
-These processes cause material in the rock to get broken up into smaller particles and transported and accumulated in oceans and lakes as sediment.
-Deposited sediments become compacted by weight of other overlapping layers if sediment cementing them together to form sedimentary rock(lithification)
- examples: sandstone and limestone

Stage 3:formation of metamorphic rock
-Sedimentary rock gets buried deep beneath the earths surface or are involved with”mountain building” ( orogenesis)
-due to the movement of the earths plates they are subjected to various levels of pressure and heat changing them into metamorphic rock
- eg crystalline from limestone undergoes the metamorphic process becomes marble

Stage 4:Completion of the cycle
Metamorphic rocks are subject to even greater pressure(melting) and are converted into igneous rocks

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4
Q

Explain the variations of the rock cycle

A

There is no inevitability about the order of the cycle
Igneous rock can be transformed into metamorphic rock without becoming a sedimentary rock via heat and pressure as well as sedimentary and metamorphic rocks may be converted to material for new sedimentary rocks

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5
Q

Explain how soil formation(pedogenesis) happens ?

A

Is the combined effect of physical, chemical, biological and human caused processes working on soil parent material.
Process begins with parent rock material is exposed to the atmosphere and organic matter or minerals that are deposited on the earths surface.

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6
Q

What determines the fertility of a soil ?

A

The type of parent rock material will determine which minerals will be predominant in the resulting soil and this effect the fertility thereof.

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7
Q

What determines what type of vegetation grows successfully?

A

Nutrient availability( not the same in all soils)

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8
Q

What has a influence on the characteristics of soil ?

A

Parent material(bedrock)
Climate
Living organisms
Topography
Time

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9
Q

Explain how the B horizon is formed

A

Formed when organic matter has accumulated and colloids are washed downwards, leaving deposits of clay, humus, iron oxide, carbonate and gypsum produce a distinctive layer called the B horizon

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10
Q

How are various soil horizons formed ?

A

movement of materials within soils

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11
Q

Give an example of how soil is developed

A

Begins with the weathering of lava flow bedrock, producing purely mineral based parent material from which the soil texture forms. This processes would happen most rapidly in a area with high natural rainfall.
Under these conditions plants(lichens) will become established quickly. After this it will escalate to larger plants with roots growing out of porous cracks in the rocks filled with minerals rich water deposits from degraded rocks. Over time the dead organic matter and finer mineral soil accumulation which then provide opportunity for further growth.

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12
Q

How long does it take for rocks to become soils ?

A

They start converting as soon as they are exposed to the environment but the process from exposed rock to mature soil is a lengthy process dependant on the type of rock, mineral qualities, and environmental factors.
Tens of thousands of years

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13
Q

What is ment by dynamic equilibrium of soils

A

Soil formation never stops it does how ever reach a point where the changes of “mature soil” have become practically imperceptible. Meaning the rate at which soil is broken down and formed is equal.

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14
Q

What are the 5 major factors in the soil forming process?

A

Climate
Organism
Topography
Rock type or parent material
How much time has past

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15
Q

What is the definition of weathering?

A

The collective process that changes rock into soil under the action of temperature, climate and other atmospheric factors.

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16
Q

Explain the process of weathering

A

-Rock breaks down physically into smaller fragments that become parent material
- also breaks down chemically and changes the compounds in the rock that dissolve in the rain and react with the air
-rock is also broken down biologically by living organisms in contact with the rock with the fragments providing organic matter to maturing soils
- plants will eventually bigin to establish themselves as the soil forming processes continues.
- wind, birds and other animals deposit seeds that may germinate further breaking down the rocks chemically and biologically and also providing nutrients for them from decomposing bio matter from pervious plants(lichens)
-this encourages the growth of small animal populations that feed upon degrading plant material.
- increasing moisture retention capabilities and in turn resulting in continual growth of plants in developing soil.

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17
Q

How long does weathering continue ?

A

It continues until all that can be weathered is broken down and the rock is no longer recognisable as rock.

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18
Q

When is weathered rock considered a soil ?

A

Only when dynamic equilibrium is reached

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19
Q

What determines the nature of mineral or inorganic components of the soil ?

A

The kind of parent rock and degree of weathering

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20
Q

What rock type is weathered more rapidly ?

A

Rocks formed under intense temperatures and pressure that cool rapidly (crystalline structures) are less stable at the earths surface so will be weathered more rapidly

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21
Q

What rocks take longer to be weathered

A

Rocks formed under intense pressure and heat but cool more slowly and later in the magma cooling process are more stable and form stronger bonds and thus more resistant to the forces of weathering

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22
Q

Define weathering

A

The combined action of all processes whereby rock is decomposed and disintegrated because of exposure at or near the earths surface

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23
Q

What changes the rate at which rocks are weathered?

A

Particle size/ area exposed to the surface
Mineral composition
Climate

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24
Q

What are the 6 different types of weathering

A

Chemical weathering(all chemical reactions that are involved in the breakdown of rocks with water)
Physical weathering( physically or mechanically weathered rock)
Animals and plants( burrowing animals moving rocks and matter up and down to and from the surface)
Crystallisation(as water evaporates moisture from rocks mineral salts develop into mineral crystals, growing and spreading mineral grains apart eventually splitting the rocks)
Temperature variations( minerals in rocks expand and shrink as temperature fluctuations happen as this happen crystals separate and causes the rocks to break eventually)
Unloading and exfoliation( cracks in rock form when pressure is released as overlaying rocks are removed allowing for expansion of newly exposed rock. As exfoliation occurs in sheets of rock the slide of allowing for slabs of cracked rocks to be further eroded.)

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25
Q

Explain what is ment by erosion

A

Is a two phase process consisting of detachment of particles from the soil mass as they are transported by erosive agents such as running water and wind. Once there is not enough energy to transport particles deposition occurs

26
Q

How is erosion different from weathering?

A

Weathering is the break down of rocks into smaller particles whereas erosion is the movement aspect of such particles

27
Q

What is deposition ?

A

When eroded( moved particles) are transported by one of the eroding agents and are finally deposited somewhere else these eroding agents become deposition agents.

28
Q

Name 5 different forms of erosion

A

Overland flow
Splash erosion
Sheet erosion
Corrosion
Hydraulic action

29
Q

Name and describe the different ways the disposition of particles takes place

A

Erosion by water- final disposition of particles usually occurs at the mouth of a stream. Called horizontal disposition when fast flowing sediment from stream empties out in slow moving larger body if water stacking on top of each other
Erosion by wind- whenever wind loses velocity it losses the ability to transport sand and must deposit it allowing the formation of landscape features.
Marine deposits- the circulation of water on the marine shelf brings nutrients from the bottom to the top and aids in organic growth of faecal pellets that eventually become cemented.

30
Q

What is the typical composition if soil ?

A

Typical soil is about 50% solids(45% mineral and 5%organic matter) and 50% voids of which half are occupied by water and half gas
The percentage soil, water and gas its highly variable but as one grows another reduces, thus staying balanced.

31
Q

What role does the pore space play in soil ?

A

Allows for the infiltration and movement of air and water which are both crucial for life existing in soil

32
Q

How do soil Horizons form ?

A

Given enough time and assuming the soil doesn’t change it will evolve profiles which consist of two or more layers reffered to as soil horizons each layer differ in properties such as texture, structure, porosity, consistency, temperature, colour and reactivity

33
Q

How do these Horizons differ ?

A

They differ greatly in thickness and lack sharp boundaries

34
Q

What are the differences in soil horizons dependent on ?

A

Type if parent material
Soil forming factors
Biological influences are strongest near the surface
Geochemical influences on soil properties increase with depth

35
Q

What horizons are mature soils typically made up out of ?

A

Include 3 major horizons A,B,C
Living components of soil is largely confined to A and B horizons(mostly A)

36
Q

What is the definition of a soil horizon ?

A

A horizontal layer of the soil whose physical features, composition and age are distinct from those above and beneath.

37
Q

How are horizons named ?

A

They are named based on the type of material of which it is composed, those materials reflect the duration of specific processes of soil formation.

38
Q

Name the 4 different properties of soil that are taken into account when classifying soils

A

Soil texture
Ph of the soil
Soil structure
Colour of the soil

39
Q

How is soil texture determined?

A

Determined by relative proportions of the individual particles of sand, silt and clay that make up the soil

40
Q

Why is soil texture important ?

A

It largely determines the water retention and transmission properties of the soil, thus determining what plant growth will occur in that area.

41
Q

Why is Ph in soil important?

A

It is a measure of hydrogen ion activity within the soil and is a measure of how acid or alkaline the soil is

42
Q

At what Ph range does the largest variety of plants occur ?

A

6.0 to 7.0 range(slightly acidic to neutral)

43
Q

Why is the interaction between soil Ph and plant nutrients important?

A

Soils higher in alkalinity or acidity can result in deficiencies or excess of certain kinds of elements essential to plant growth or survival

44
Q

What other roll does Ph in the soil play with regards to levels of nitrogen, phosphorus and sulphur?

A

It can effect the activity of micro organisms which then effects the levels of nitrogen, phosphorus and sulphur

45
Q

What does soil structure refer to ?

A

Refers to the way in which soil grains are grouped together into larger pieces held together by solid colloids.

46
Q

What does soil structure influence?

A

The rate at which water is absorbed by the soil, the susceptibility of the soil to erosion, and how easy it is for plant growth to

47
Q

Define the differences particle size has on water retention

A

Sand- vary in size depending on how kong they’ve been exposed to weathering, many spaces between particles poor water retention
silt- diameter of particles smaller than sand meaning space between particles are smaller= more water retention and nutrient retention
clay - space between particles much smaller meaning water molecules struggle to move through meaning that the clay soil gets water logged and when it dries it cracks making it extremely difficult for plants too survive and thrive in it.

48
Q

What role does soil colour play ?

A

Generally dark soils are more fertile than lighter soils
Soils with red/ redish brown- contain large portions of iron oxide in tropical areas tend to be infertile due to the lack of hummus
Yellow/ yellowish soils- low fertility( sign of poor drainage)
Grayish/ blueish soils suffer from poor drainage(waterlogging) and oxygen deficiency. A white colour may be as result of alkaline salts in the soil

49
Q

What are the 4 functions of soil ?

A

-Provides a medium for the growth of plants
-provides a means of water storage, supply and purification
- is a modifier of earths atmosphere
- is a habitat or ecosystem for a multitude of organisms

50
Q

What is the role of all of these functions of soils ?

A

They continuously modify the soil and its properties
Soil acts as a carbon reservoir for the carbon cycle
Acts as a engineering medium
A habitat for soil organisms
Recycling system for organic wastes and nutrients
Regulator of water quality
Medium for plant growth
Modifier of earths genetic composition

51
Q

Explain what is ment by soil as a “service provider”

A

Natural protector of seeds and plants
Provides physical support system for plants
Retains and delivers nutrients to plants
In turn provides animals with a food source(including humans)
Can hold and release water providing plants with flood protection water filtration and purification
Also plays an important role in management, processing and detoxification of wastes and can render most harmful substances harmless to the environment

52
Q

What is ment by soil ecosystem?

A

Soils are rich eco systems composed of both living and non- living matter with a multitude of interactions between them

53
Q

Where do soil and soil ecosystems play a important role ?

A

They play a very important role in the natural ecological cycles such as the carbon, nitrogen, oxygen, water and nutrients cycles

54
Q

What are the roles of soil ecosystems ?

A

Waste decomposition, acting as a water filtration system and degrading environmental contaminants.

55
Q

The diversity and abundance of life that exists within the soil is greater than any other ecosystem, True or False ?

A

True

56
Q

What are essential nutrients? give 5 examples

A

Nutrients that are required for plants to complete their life cycle eg. Carbon,
Hydrogen, oxygen, sulphur and nitrogen

57
Q

What are non essential nutrients?

A

Nutrients not responsible for a plant to complete its life cycle, but that will enhance plant growth

58
Q

How do plants take up water ?

A

Via osmotic absorption through the xylem flow due to a higher concentration of salts in the plant then in the soil solution ionised nutrients are attracted to the high salt content.

59
Q

Explain why the soil food web is an integral part of ecosystem and landscape processes

A

-Soil organisms decompose organic compounds
-they remove nitrogen and other nutrients that might enter groundwater
- they fix nitrogen from the atmosphere making them available to plants
- many organisms enhance soil aggregation and porosity, increasing infiltration and reducing run off
- soil organisms prey on crop pests and are food for above ground animals

60
Q

What is the soil food web ?

A

A community of organisms living all or part if their lives in the soil

61
Q

Explain the major functions and effects of life in the soil

A

Photosynthesise(plants/algea/bacteria)- capture energy
Decomposers(bacteria/fungi)- break down residue
Mutualists(bacteria/fungi)- enhance plant growth
Bacterial feeders(protozoa/ Nematodes)- Graze
Fungal feeders(Micro-arthropods/Nematodes)-Graze
Shredders(earthworms/Macro-arthropods)- break down residue and enhance soil Structure
High- level predators(larger arthropods, mice, shrews, birds and other above ground mammals)- control populations

FGASA Level 2 (14 decks)

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