4.2 - Soil Formation and Erosion Flashcards
What is soil?
- A mixture of geologic (rock) and organic (living) components
- Sand, silt, and clay make up soil
- Humus: main organic part of soil (broken down biomass like leaves, dead animals, waste, etc.)
- Nutrients: ammonium, phosphates, nitrates
- Water and air
- living organisms
What is humus?
main organic part of soil (broken down biomass like leaves, dead animals, waste, etc.)
What are nutrients?
ammonium, phosphates, nitrates
What 3 rocks make up soil?
- silt
- clay
- sand
How does soil impact roots?
anchors plants and provides water, shelter, and nutrients for growth
How does soil impact water?
filters rainwater and runoff by trapping pollutants in pore spaces and plant roots. Clean water enters groundwater and aquifers
How does soil impact nutrient recycling?
Home to decomposers that break down dead organic matter and return nutrients to the soil
How does soil impact habitat?
provides habitat for organisms like earthworms, fungi, bacteria, moles, slugs, etc
What are the 4 main things soil impacts/involve
- Plants
- Water
- Nutrient/Nutrient Recycling
- Habitats
What is weathering?
The breakdown of rocks into smaller pieces
What are the 3 types of weathering
- Physical (wind, rain, freezing/thawing of ice)
- Biological (roots of tree crack rocks)
- Chemical (acid rain, acids from moss/lichens)
What does weathering of rocks lead to
Soil formation
- broken into smaller and smaller pieces
- carried away and deposited by erosion
What is erosion?
- Transport of weathered rock fragments by wind and rain
- Carried to a new location and deposited (deposition)
Explain what happens to soil over time
Over time soil goes form being immature, to young, to mature soil.
What are the two types of soil formation?
- From Below
- From Above
Explain soil formation from below
- weathering of parent material (bedrock) produces smaller and smaller fragments that make up geological/inorganic part of soil
- small parts make their way up the soil
- Sand, silt, clay is created this way
- minerals
Explain soil formation from above
- breakdown of organic matter adds humus to soil
- erosion deposits soil particles from other areas, adding to soil
Explain effects on soil formation
- parental material: soil pH, nutrient content
- topography: steep slope = too much erosion; level ground = deposition
- Climate: warmer = faster breakdown of organic matter; more precipitation = more weathering, erosion, and deposition
- organisms: soil organisms like bacteria, fungi, worms breakdown organic matter
List the soil horizons in order with depth
- O - 0-.1m
- A - .1-.3m
- B - .3-1m
- C - 1-1.3m
Describe the soil horizons
- O-horizon - layer of organic matter (plants root, dead leaves, animal waste, etc.) on top of soil
- provides nutrients and limits H2O loss to evaporation - A-horizon (topsoil) - layer of humus (decomposed organic matter) and minerals from parent material
- has most biological activity (earthworms, soil microbes) breaking down organic matter to release nutrients - B-horizon (subsoil) - lighter layer below topsoil mostly made of minerals with little to no organic matter
- contains some nutrients
- typically more clay less humus - C-horizon - least weathers soil that is closest to parent material, sometimes called bedrock
*** in some soils, an E horizon occurs beneath either the O or A horizon
What is soil degradation
the loss of the ability of soil to support plant growth
3 ways for soil degradition
- Loss of topsoil
- Compaction
- Nutrient depletion
Explain loss of topsoil as a soil degradation
- tilling (turning soil for agriculture) and loss of vegetation disturb topsoil and make it more easily eroded by wind and rain
- loss of topsoil dries out soil, removes nutrients and soil organisms that recycle nutrients
Explain compaction as soil degradation
- compression of soil by machines (tractors, bulldozers, etc.), grazing livestock, and humans reduces the ability to hold moisture
- dry soil erodes more easily
- dry soil supports less plant growth, less root structure, leading to more erosion
Explain nutrient depletion as soil degradation
- repeatedly growing crops on the same soil removes key nutrients (N, P, Ka, Mg) over time
- reduces ability to grow future crops
What is deposition?
the laying down of sediment carried by wind, flowing water, the sea, or ice
