R2102 1.1 Describe the formation of typical mineral soils

Question 1

What is soil texture?

Answer 1

Describes the relative quantities of sand, silt and clay particles in a soil

Question 2

What is soil structure?

Answer 2

Describes the arrangement of soil particles and the spaces between them

Question 3

What does a naturally fertile soil provide for plants? (4)

Answer 3

1. Water
2. Air (oxygen)
3. Nutrients
4. Anchorage

Question 4

Types of rock (3)

Answer 4

1. Igneous e.g. Granite
2. Sedimentary rock e.g. Sandstone
3. Metamorphic rock e.g. Slate

Question 5

Types of physical weathering processes (5)

Answer 5

1. Water - moving water abrading or scouring rocks
2. Wind - abrasive particles ‘sand blasting’ exposed rock
3. Heat - Sun, heating and cooling of rocks lead to surfaces breaking away
4. Frost - water freezes and expands
5. Glacier - enormous forces pluck rock away and large rocks embedded in the ice scour away the rock with which in comes into contact

Mainly occurs on exposed rock - not that protected by thick soil layer

Question 6

Types of physical weathering processes (5)

Answer 6

1. Water - moving water abrading or scouring rocks
2. Wind - abrasive particles ‘sand blasting’ exposed rock
3. Heat - Sun, heating and cooling of rocks lead to surfaces breaking away
4. Frost - water freezes and expands
5. Glacier - enormous forces pluck rock away and large rocks embedded in the ice scour away the rock with which in comes into contact

Mainly occurs on exposed rock - not that protected by thick soil layer

Question 7

Types of chemical weathering (1)

Answer 7

1. Carbonic acid. As carbon dioxide from the air dissolves in rain it forms Carbonic acid which dissolves the Calicum Carbonate in chalk and limestone

Question 8

Types of biological weathering (3)?

Answer 8

1. Combination of physical (mechanical) and chemical weathering
2. Mosses and lichens on rock produce large quantites of carbonic acid
3. Roots penetrating gaps in rocks in search of water

Question 9

What is parent rock?

Answer 9

Rock from which the soil is made

Question 10

What is weathering?

Answer 10

The breakdown of rock

Question 11

What is erosion?

Answer 11

The movement of rock fragments and soil broken down by weathering

Question 12

Four processes that help for particular soils

Answer 12

1. Additions - from outside sources such as organic matter from leaves, dust from atmosphere or soluble salts from groundwater
2. Losses - material leached out to groundwater, erosion of surface material
3. Transformation - Soil constituents changing from one form to another e.g. by mineral weathering and breakdown of organic matter
4. Translocation - Movement of organic and inorganic matter from one horizon to another. Washed downwards by water or moved by soil organisms such as earthworms

Question 13

Erosion processes (4)

Answer 13

1. Gravity - fragments on loss slopes travel downhill e.g. scree
2. Water e.g. Alluvial soil - layers of sand and silt left behind with organic matter in flood planes
3. Wind - Particles carried by wind, leading to large areas of sandy materials which form loess soils
4. Glaciers - soils left by glaciers are known as boulder-clay

Question 14

What is the soil horizon?

Answer 14

A specific layer in the soil seen by digging a soil pit

Question 15

What is a soil profile?

Answer 15

Vertical sections through the soil. They show the different layers

Question 16

What are the main layers in a soil profile (4)

Answer 16

1. Horizon O - organic layer
2. Horizon A - topsoil
3. Horizon B - Subsoil
4. Horizon C - Parent material

Question 17

What is in the organic layer (Horizon O)?

Answer 17

Layer of fresh plant litter which has yet to be incorporated into the soil (sometimes know as Horizon AO)

Question 18

What is the topsoil (Horizon A) (6)?

Answer 18

1. Material at top of soil profile
2. Usually dark brown or black in colour
3. Contains greatest proportion of orgainic matter
4. Most affected by the actions of living things
5. Most roots found in this layer, abundant plant and animal life
6. Typically 10-40cm deep

Question 19

What is subsoil (Horizon B)(3)?

Answer 19

1. Layer below the cultivated layer
2. Lighter in colour because of low organic matter level. Colour depends greatly on the chemicals coating the particles
3. Material transported down from topsoil may accumulate here, finer particles washed down.
4. Reduced biological activity lead to poorer air and water movement

Question 20

What is the parent material (Horizon C)

Answer 20

Material from which the soil has developed and generally consists of almost unaltered rock. The original nature of the rock can be seen.