Unit 5.1: soils

Question 1

what is biogeography?

Answer 1

study of geography of life and how it changes through space and time.

Question 2

what is the biosphere?

Answer 2

the focus of biogeography. between the lithosphere and the atmosphere.

Question 3

what is the biosphere divided in?

Answer 3

1. soil material that is used by flora

2. the distribution of flora and fauna

Question 4

what is pedogenesis?

Answer 4

the process of soil formation: weathering of rocks, activities of organisms, movement of rainwater, time.

Question 5

what is pedology?

Answer 5

study of the origin, classification, distribution, and description of soil

Question 6

what is soil?

Answer 6

uppermost portion of regolith and has been modified by organisms. also influenced by atmosphere, hydrosphere, and lithosphere.

Question 7

what are two characteristics of soil?

Answer 7

• forms slowly and is easily destroyed.

- most of life on Earth depends on it

Question 8

what is bedrock?

Answer 8

rock that is structurally part of and connected to earths crust. no weathering or erosion

Question 9

what is regolith?

Answer 9

loose earth material that covers bedrock

Question 10

what is soil composed of?

Answer 10

1. Minerals: inorganic material from rock; supply nutrients to green plants (sand, silt, clay)
2. organic material: paint and animal matter; releases nutrients into the soil or combines with mineral particles.
3. water
4. air

Question 11

what are horizons?

Answer 11

horizontal zones in the soil column with various characteristics

Question 12

what are the various horizons?

Answer 12

O horizon: (Humus) organic horizon, topmost layer composed mostly of organic matter

A horizon: (topsoil) rich in organic material; where most plants roots are, dark in colour

E horizon: (transition) lighter in colour and formed from elevation and leaching

B horizon: (subsoil) formed by illuviation or deposition of leached material

C horizon: (weathered bedrock) no or limited amount of organic material; lower boundary of true soil

R horizon: (solid bedrock) mostly solid, unweathered bedrock

Question 13

what is elevation?

Answer 13

water carries soil particles and weathered material down the soil column

Question 14

what is leaching?

Answer 14

movement of dissolved material downward by rainwater

Question 15

what is illuviation?

Answer 15

deposition of weathered material deeper in soil

Question 16

soil horizons can be defined by what characteristics?

Answer 16

1. soil texture
2. soil structure
3. soil colour

Question 17

how does soil texture affect soil horizons?

Answer 17

the size of particles in soil affect the permeability of water. there’s clay (

Question 18

what is loam?

Answer 18

soil that contains 20% clay, 40% silt, 40% sand, and lots of organic material

Question 19

in terms of soil structure, what are the 4 basic structures of the grain?

Answer 19

• Platy structure: layered soil particles that look like flakes stacked horizontally.
• prismatic structure: soil particles arranged in columns giving soil vertical strength.
• blocky structure: irregularly shaped soil particles
• spheroidal structure: soil parts are very small and nearly round in shape

Question 20

what do various soil colours mean?

Answer 20

• dark brown/ black: high presence of organic matter (in temperate grasslands)
• red: indicates strong chemical weathering, iron and oxidation (tropical rainforest)
• grey: indicates heavy leaching (boreal forest)

Question 21

where does soil develop fastest?

Answer 21

where chemical weathering predominates.

Question 22

what factors control the rate of soil formation?

Answer 22

• parent material: the original bedrock that the soil is formed from. hard material will take longer to develop
• climate: temperature and precipitaiton controls amount of weathering and the breaking down of bedrock and regolith into soil particles.
• topography: slope of bedrock or environment will affect the soil formation. a steep slope will typically not have thick soil layer due to mass movement.
• plants and animals: flora & fauna will not affect uptake of material in the soil, but will add to organic material as they die.
• time: soil particles require a long time to form

Question 23

what factors of soil formation are active and what are passive?

Answer 23

active; climate and plants/animals because they supply energy

passive: parent material, topography, and time because they receive energy..