AP Environmental Science › Soil Formation, Composition, and Properties
Which element is not a component of soil?
None of these
Living organisms
Mineral material
Partially decomposed organic matter
All of these components make up soil. Differences in ratios of these components account for different soil types.
The soil beneath your feet is stratified into layers that help us understand how soil is formed. If you collected a soil sample that contained accumulations of clay and subsoil, from which horizon (layer) did this soil come?
B Horizon
O Horizon
A Horizon
C Horizon
R Horizon
The correct response is B Horizon. The B horizon is referred to as the zone of accumulation because all the clay, minerals, and subsoil that is washed into it via illuviation from the overlying layers of soil. The B horizon is usually dark red or brownish due to the presence of clay and iron oxides.
Which soil layer is composed of weathered rock (parent material) and contains little to no organic matter?
The C Horizon
The O Horizon
The D Horizon
The B Horizon
The A Horizon
The O Horizon is composed of humus (organic matter), the A Horizon is a mixture of minerals and organic matter, the B Horizon is composed mainly of minerals and the D horizon is solid bedrock. The C Horizon best fits this definition, as it is the layer above the bedrock, consisting mostly of weathered rock fragments.
What is the brown insoluble particles from partially decomposed organic matter?
Humus
Waterlog
Rill
Clay
Minerals
The correct response is humus. This is one of the most important components to soil communities. Humus is formed as things like leaves, branches, and other vegetation breakdown (slowly) over time. Earthworms and microbes help speed up the process of breaking down dead organic matter into humus.
Soil scientists help farmers discover how healthy their soils are. When a soil scientist measures the ability of soil particles to clump together, what soil property are they measuring?
Cohesion
Sensitivity
Strength
Plasticity
The correct response is cohesion. This property measures how well a soil clumps together or breaks apart.
Conserving our natural resources is one of the challenging issues of the 21st century. What important natural resource is comprised of clay, silt, pebbles, and sand?
Soil
Coal
Fossil fuels
Iron
The correct response is soil. Soil is a mix of sand, clay, pebbles, and silt. It is the foundation of all our ecosystems.
What are soil horizons?
The horizontal layers of soils
The materials that make up the soil
The chemical properties of the soil
The physical properties of the soil
The result of human disturbances
There are six types of soil horizons and each has different chemical or physical properties. Each type of soil has a different number of horizons. The horizons start at the parent material (bedrock) and continue up to the surface.
__________ is soil with the smallest particles. (Less than 0.002mm diameter).
Clay
Silt
Sand
Loam
Clay has the smallest particles, followed by silt, which contains larger particles than clay, but smaller particles than sand. Loam is a mixture of these three types of soil.
Soil is stratified into different layers, called horizons. Which horizon contains freshly fallen leaves, plant litter, and lots of organic matter?
O Horizon
A Horizon
B Horizon
C Horizon
R Horizon
The correct response is O Horizon. This O horizon is the layer closest to the surface - typically between the depths of 0 to 2 inches, and contains freshly fallen leaves, plant litter, and lots of other organic matter.
Which of the following choices best describes the process by which soil horizons accumulate material such as iron, clay, organic compounds, and aluminum?
Illuviation
Innervation
Saturation
None of these
Leaching occurs when percolating water transports materials from the top soil layers. Usually, these materials are illuviated(deposited) to a lower level.