Unit 5: Soil Formation and Layers Flashcards
Weathering
Occurs when rock is exposed to air, water, certain chemical compounds, or biological agents.
Three types of weathering
Physical, chemical, and biological
Erosion
The physical removal of rock fragments from a landscape.
Soil horizon
A horizontal layer in a soil defined by physical features.
How does soil form?
Parent rock is weathered and erosion causes debris and organic matter to accumulate and eventually become mature soil.
5 factors that determine the properties of soil
Parent material, climate, topography, organisms, and time.
Ecosystem services soil provides
Provides plants with nutrients, stores water, filters water.
Order of soil horizons
O, A, E, B, C
O horizon
Organic matter in various stages of decomposition.
A horizon
Top soil, zone of overlying organic material mixed with underlying mineral material.
E horizon
Zone of leaching of metals and nutrients; occurs in some soils beneath either the O or the A.
B horizon
Subsoil, zone of accumulation of metals and nutrients.
C horizon
Subsoil, least-weathered portion of the soil profile, similar to the parent material.
Physical weathering
Wind, rain, thawing ice
Chemical weathering
Acids, bases
Biological weathering
Organisms
Types of soil degradation
Desertification, salinization, water logging, compaction.
How does parent material affect soil formation?
Soil pH, nutrient content
How does climate affect soil formation?
The amount of soil that forms.
How does topography affect soil formation?
Steep slope causes a lot of erosion.
Desertification
Drought and overgrazing in semiarid and arid regions causing loss of biodiversity and productive capacity.
Salinization
Too much salt because of over irrigation; irrigated water contains salt that is left behind after water evaporates.
Water logging
Plant roots lack oxygen when soil is excessively irrigated or poorly drained and air spaces are filled.
Compaction
Compression of soil by machines, grazing livestock, and humans reduces ability to hold moisture.
