Ch 18 the geography of soils

Question 1

Is soil an open or closed system?

Answer 1

Soil is an open system as it absorbs longwave radiation (surroundings are atmosphere, plants, etc.)

Question 2

Significance of soil:

Answer 2

important for storing carbon, and for plants in general

Question 3

How is soil formed?

Answer 3

Bedrock is the parent material from which weathered regolith develops

regolith is broken up rock due to weathering

As regolith weathers, the loose surface material that results becomes the basis for soil development

Question 4

True or false:

Many soils exhibit the imprint of past climates

Answer 4

True

Question 5

organic content, water, movement, physical and chemical characteristics determined by:

Answer 5

vegetation, bacteria, and animals

Question 6

Thicker soil -)
Thinner soil -)
Dryer soil-)
Moist soil -)

Answer 6

Plateaus and valleys
steep slopes
more sun/insulation
away from radiation

Question 7

True of false:

Soils develop more quickly from bedrock than sediments

Answer 7

false

Question 8

True or false:

Soils in warmer or wetter climates develop faster than soils in cooler
or drier climates

Answer 8

True

Question 9

Soil profile:

Answer 9

vertical section of soil that extends from the surface to the deepest extent of plant roots or to the point where regolith or bedrock is encountered

Question 10

O horizon

Answer 10

The organic horizon occurs in Organic soils

• Commonly located above mineral soils, but sometimes buried beneath them
• > 17 % organic C (> 30 % organic matter) by weight
• O horizon is poorly drained, peat
• L, F, H horizons are well drained, folic (leaf)

Question 11

A horizon

Answer 11

• Mineral horizon formed at or near the soil surface, containing less than 17% organic C by weight
• Ah = accumulation of soil organic matter (SOM) = dark
• Ae = Removal of clay, SOM, iron, or aluminum = light.

Question 12

B horizon

Answer 12

mineral horizon where clays, aluminum, and iron accumulate

• may have reddish and brown hues

Question 13

C Horizon

Answer 13

A mineral horizon made up of weathered parent material (i.e., regolith).

Minimally affected by soil processes occurring in the O, A and B horizons,
i.e., outside the zone of biological influence

Question 14

R horizon

Answer 14

Unconsolidated (loose) rock material or consolidated bedrock layer

Question 15

Soil texture depends on:

Answer 15

The mixture of different
soil particle sizes

Question 16

Soil bulk density equation:

Answer 16

(Mass solids/total volume)
in g/cm cubed

Useful for determining if the soil is compacted

Question 17

Soil porosity equation:

Answer 17

(Volume pores/total volume) x 100

Soil pores can be filled with air or water or both

Question 18

Soil moisture equation:

Answer 18

(volume water/total volume) x 100

Question 19

Soil colloids:

Answer 19

• Tiny particles of clay or organic material suspended in soil
• negatively charged so attracts positive ions
• criitcal for plant growth

Question 20

Acid peat soils acidity:
(humid regions)

Answer 20

7.0 -) 3.0

Question 21

Alkali mineral soils:
(arid regions)

Answer 21

7.0 -) 11.0

Question 22

Soil erosion:

Answer 22

The movement of soil from one area to another, resulting in losses and accumulations

removes topsoil

Question 23

Desertification:

Answer 23

Land degradation
in arid and semi-
arid regions

The expansion of
deserts

Caused by
deforestation, poor
agricultural
practices, overgrazing, soil
salinization, etc.

Climate change
causing poleward movement of subtropical high - pressure zones

Question 24

pedogenic regime:

Answer 24

A specific soil forming process keyed to a specific climatic regime

Question 25

pedogenic regimes include:

Answer 25

Laterization: Happens in humid, warm climates (tropics/subtropics); leaches nutrients out of the soil.

Salinization: Occurs in dry climates with high evaporation; leaves salts behind in the soil.

Calcification: Found in continental climates; builds up calcium carbonates in the soil.

Podsolization: Happens in cool forest climates; causes acidic soil.

Gleysation: Found in cold, wet areas with poor drainage; creates a waterlogged, grey clay layer with humus.