Unit 5.1: soils Flashcards
what is biogeography?
study of geography of life and how it changes through space and time.
what is the biosphere?
the focus of biogeography. between the lithosphere and the atmosphere.
what is the biosphere divided in?
- soil material that is used by flora
2. the distribution of flora and fauna
what is pedogenesis?
the process of soil formation: weathering of rocks, activities of organisms, movement of rainwater, time.
what is pedology?
study of the origin, classification, distribution, and description of soil
what is soil?
uppermost portion of regolith and has been modified by organisms. also influenced by atmosphere, hydrosphere, and lithosphere.
what are two characteristics of soil?
- forms slowly and is easily destroyed.
- most of life on Earth depends on it
what is bedrock?
rock that is structurally part of and connected to earths crust. no weathering or erosion
what is regolith?
loose earth material that covers bedrock
what is soil composed of?
- Minerals: inorganic material from rock; supply nutrients to green plants (sand, silt, clay)
- organic material: paint and animal matter; releases nutrients into the soil or combines with mineral particles.
- water
- air
what are horizons?
horizontal zones in the soil column with various characteristics
what are the various horizons?
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
what is elevation?
water carries soil particles and weathered material down the soil column
what is leaching?
movement of dissolved material downward by rainwater
what is illuviation?
deposition of weathered material deeper in soil
soil horizons can be defined by what characteristics?
- soil texture
- soil structure
- soil colour
how does soil texture affect soil horizons?
the size of particles in soil affect the permeability of water. there’s clay (
what is loam?
soil that contains 20% clay, 40% silt, 40% sand, and lots of organic material
in terms of soil structure, what are the 4 basic structures of the grain?
- 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
what do various soil colours mean?
- 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)
where does soil develop fastest?
where chemical weathering predominates.
what factors control the rate of soil formation?
- 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
what factors of soil formation are active and what are passive?
active; climate and plants/animals because they supply energy
passive: parent material, topography, and time because they receive energy..
