7 Soils

Question 1

weathering

Answer 1

the disintegration (physical breakdown) and decomposition (chemical alteration) of rocks at or near the earths surface, without any movement of the materials

Question 2

mass wasting

Answer 2

the movement of material down slope under the influence of gravity

Question 3

erosion

Answer 3

the physical movement of material by a medium such as water wind or ice

Question 4

frost wedging or shattering

Answer 4

a type of weathering where water fills the internal spaces of rock, when the water freezes it expands applying pressure to the rock. the rock will eventually crack and break up

Question 5

How can biological activity cause weathering

Answer 5

-roots of trees and shrubs often grow into cracks and joints of rocks. as the trees grow, they exert pressure on the rock causing the crack to widen.

-burrowing animals can weaken land areas, ultimately leading to collapse with the loosened and broken rocks and soil easily washed away or exposed to further weather effects

Question 6

salt crystallisation

Answer 6

when water evaporates it leaves behind dissolved mineral content. these minerals then crystallise. the froth applies pressure to enclosing rock

Question 7

soil

Answer 7

soil is the upper layer of the earths crust, supporting plant growth and providing a critical bridge between and biosphere and mineral content of the geosphere.
-it consists of minerals, organic matter, air, water and living organisms

Question 8

climate affecting soils

Answer 8

the combined effects of rainfall, tempt and seasonal changes.
-in cold dry regions (deserts and polar and alpine environments) soils are typically thin and contain little organic matter
-in hot and wet environments (equatorial and tropical regions) there are better plant growth which adds organic matter after decomposition, resulting in thick soils rich in organic matter

Question 9

What does Horizon A consist of?

Answer 9

Contains humus and is a zone full of intense biological activity by plant roots worms insects microorganisms and other life forms.
Old, well developed soils contain less soluble minerals due to leaching, leaving behind insoluble minerals like clay and quartz

Question 10

Humus

Answer 10

Humus is dark, organic material that forms in soil when plant and animal matter decays.

Question 11

What does Horizon B consist of?

Answer 11

Bright colours and contains little organic matter except deep plant roots.
Contains concentrated soluble minerals and iron oxides from leaching

Question 12

What does Horizon C consist of?

Answer 12

Contains clay mixed with Brocken pieces of bedrock

Question 13

topography

Answer 13

-soils on steep slopes are usually thinner than those on flat or gently sloping areas
-sloping soils move downhill with erosion

Question 14

What does Bedrock consist of?

Answer 14

Bedrock is the underlying rock of an environment formed from weathered and broken down rock. It doesn’t show real development in soil so not strictly considered a horizon.

Question 15

water movement (two types and effects)

Answer 15

-water movement within soil can be lateral (sideways) and vertical (leaching)
-lateral movement causes transport of soluble material or even entire soil horizons
-vertical movement of water through soil is called leaching. it removes soluble minerals from the A horizon, then concentrated in the B horizon

Question 16

Time

Answer 16

-is required for all of the factors mentioned above.
-after an event like a landslide, that mixes soil into an unaltered mass, it can take between hundred and thousands of years for a clear horizon to redevelop

Question 17

What is responsible for soil thickness?

Answer 17

Rocks which are more resistant to physical/chemical breakdown form thin rocks eg quartzite compared to thick soils composed of rocks which easily breakdown eg limestone.

Question 18

What are the inputs of the soil system?

Answer 18

• precipitation and ground water flow
• atmospheric gases, e.g. oxygen, nitrogen, and carbon dioxide
• mineral nutrients from weathered rock
• organic material from dead organisms
• Solar energy

Question 19

What are the outputs of the soil system?

Answer 19

• water loss through transpiration and evaporation
• Nutrients taken by plants
• Mineral nutrients, lost through leaching an eluviation
• loss of soil by erosion or slope movement
• Permanent loss of nutrients due to clearing of vegetation including harvesting

Question 20

What causes horizons or soil profiles?

Answer 20

Due to processes that organise soil components
- weathering of bedrock
- leaching
- accumulation of minerals where groundwater conditions cause precipitation
- eluviation (movement of dissolved or suspended mineral matter)
- breakdown or organic matter into humus

Question 21

What are zonal soils?

Answer 21

Refers to a strong, old, well developed soil with distinct horizons.

Question 22

What are azonal soils?

Answer 22

Azonal soils are the soils that lack well developed horizons because of immaturity or other factors that have prevented their development;
Usually found in steep slopes or retreating coastlines.
They have characteristics of their parent rock.
The opposite to zonal soils.

Question 23

What is horizon O?

Answer 23

Represents a surface layer consisting of leaf litter and loose organic material. Is home to bacteria, fungi, insects, and other organisms which breakdown material to form humus.

Question 24

What are soils and how do they form?

Answer 24

Soils form at the intersection between the geosphere atmosphere, hydrosphere, and biosphere also known as the regolith.
Six factors contribute to the production of soil;
1 the parent rock material present
2 the climate
3 the topography
4 organisms 
5 passage of time
6 human activity

Question 25

What is the composition of a typical, mature soil?

Answer 25

45%, air and water
40% mineral material
10% organic
5% biotic

Question 26

How can Human activity affect soil?

Answer 26

• Addition of fertilisers and mineral supplements changes chemical composition.
• deforestation and harvesting removes nutrients and organic matter impacting soil quality and structure
• Urbanisation changes drainage patterns in a landscape isolating soils from biotic influences
• Excessive irrigation can wash, soluble nutrients out of surface layers or even strip them from landscape altogether.

Question 27



Question 28

How do organisms affect soil?

Answer 28

They build up and store nutrients so when they are decomposed, this nutrients is released into the soil eventually creating humus.

Burrowing animals and insects are also important as they mix water and air through the soil, redistributing minerals and organic components.

Question 29



Question 30

How does climate affect soils?

Answer 30

Climate affects temperatures, water air and organic content which are some of the fundamental components of soil.
c. Intuencis a narc and animal life supported in an area.
Some climates with soil-climate correlations include
• Humid Tropical Regions
• Arid Regions
• Temperate Regions
• Cold climates with little rainfall

Question 31

What are conditions of tropical soils

Answer 31

Humid Tropical Regions - heavy rainfall and high temperatures produce rapid chemical weathering and luxuriant plant growth. Soils may have a deep profile, with weathering extending to 30-50 metres below the surface. Strong leaching and eluviation remove most nutrients from the soil, as well as all but the most stable minerals. Soils in these regions generally have a low fertility.

Question 32

What are soil components of arid regions?

Answer 32

• Arid Regions - regardless of temperature, the lack of water in the environment limits the degree of both chemical and physical weathering and hence the formation of regolith. Physical erosion is dominated by windblown sand and intermittent flash floods. There is limited vegetation growth and hence little humus, so soils are poorly developed.

Question 33

What are cellular components of temperate regions?

Answer 33

• Temperate Regions - physical and chemical weathering produce a wide variety of soil profile types.

Question 34

What are soil conditions of cold climates?

Answer 34

• Cold Climates with Moderate Rainfall - low temperatures mean chemical weathering is slow, with little alteration of parent minerals. Physical weathering is dominated by frost shattering. Little vegetation growth, so there is limited soil development.

Question 35

Parent material

Answer 35

The breakdowns and modification of local geological substrates make up soil chemical and mineral composition.