Chapter 7

Question 1

Soil definition/formation

Answer 1

if a sedimentary layer isn’t transported, eventually vegetation/rain can break it down and form a soil layer. Soil contains dirt, but soil also contains organic matter/rain water/biologic materials is incorporated into the soil’s ecosystem (bacteria, fungi, etc.). Occurs above and right below the surface. Open pore spaces in the soil fills with air/water which changes it. Soil contains micro-organisms. Nitrogen cycle interacts with pore spaces in soil, which creates vegetation

• to be soil, it must have organic matter (liquid, gases, or organisms) and support vegetation (or life)
• soils and agriculture forms through physical and chemical weathering

Question 2

Ideal Soil Horizons

Answer 2

distinct zones (of soil) with distinct processes (from top/above ground, to bottom): O layer is mainly roots, darker color, indicates it’s made of organic material and carbon, made of humus, minimal salt debris. Decomposition occurs here

• A layer has similar properties to O layer, A horizon is organic matter mixed with sediments (clays, salts, sands), chemical weathering (leaches, when water infiltrates and picks up ions). O and A layers are made up of top soil, valuable to agriculture and supporting vegetation.
• E horizon also experiences leaching (chemical reactions), not part of the top soil.
• O, A, and E horizons make up the “zone of leaching” (chemical reactions between water and sediments)
• B horizon is where clay starts to form, called “zone of accumulation” and sub-soil.
• C is called R (rock) horizon, not much accumulation or veeching occurs here. Sediment that’s been physically and chemically weathered/fractured. Not part of useful soil, usually made of broken up bedrock.

Question 3

Soil and Climate

Answer 3

heavy rainfall and hot weather means strong chemical reactions, but hotter/dry climates reduce the rates of chemical reactions and nutrients in soil. As climates get colder and drier (less rain), physical weathering/reactions are more likely to occur, at a faster rate. Soil formation is much slower in drier climates. Excess/heavy rainfall results in lack of nutrients in soil. Salts and carbonates can be precipitated and build up (especially in hot/dry conditions), effects soil

Question 4

Soil Erosion

Answer 4

the progressive removal of soil material due to flowing water, wind, or gravity; such a process can be exacerbated (made worse) through human actions which might destroy agricultural lands.
-gravity, wind, water (floods), can transport/move sediment and soil.

Question 5

soil environmental issues

Answer 5

Urbanization: requires much construction (soil is removed, lost/disturbed), increases run-off (harder for the ground to be absorbed on paved surfaces), external sediment may be brought in during construction and mixed with existent soil