AP Environmental Science : Soil Formation, Composition, and Properties

Study concepts, example questions & explanations for AP Environmental Science

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Example Questions

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Example Question #1 : Soil Formation, Composition, And Properties

Which soil layer is composed of weathered rock (parent material) and contains little to no organic matter?

Possible Answers:

The C Horizon

The O Horizon

The A Horizon

The D Horizon

The B Horizon

Correct answer:

The C Horizon

Explanation:

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.

Example Question #2 : Soil Formation, Composition, And Properties

Which of the following choices best describes the process by which soil horizons accumulate material such as iron, clay, organic compounds, and aluminum?

Possible Answers:

Saturation

None of these

Innervation

Illuviation

Correct answer:

Illuviation

Explanation:

Leaching occurs when percolating water transports materials from the top soil layers. Usually, these materials are illuviated (deposited) to a lower level.

Example Question #3 : Soil Formation, Composition, And Properties

Which element is not a component of soil?

Possible Answers:

Mineral material

None of these

Partially decomposed organic matter

Living organisms

Correct answer:

None of these

Explanation:

All of these components make up soil. Differences in ratios of these components account for different soil types.

Example Question #4 : Soil Formation, Composition, And Properties

__________ is soil with the smallest particles. (Less than 0.002mm diameter). 

Possible Answers:

Clay

Loam

Silt

Sand

Correct answer:

Clay

Explanation:

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.

Example Question #5 : Soil Formation, Composition, And Properties

Soil is categorized by composition and depth. Each category is referred to as a __________.

Possible Answers:

cast

horizon

level

group

Correct answer:

horizon

Explanation:

Soil categories are referred to as "horizons." Additionally, a vertical cross section of soil horizons is called a "profile."

Example Question #6 : Soil Formation, Composition, And Properties

Which type of rock is found deep below the Earth's surface and is formed by intense heat and pressure? 

Possible Answers:

None of these types

Sedimentary

Metamorphic

Igneous

Correct answer:

Metamorphic

Explanation:

Metamorphic rock is the only kind of rock that is formed below the Earth's crust. Igneous rock is formed by lava and volcanic activity. Sedimentary rock is formed by the collection of sand and other microscopic components that are fused together. Generally, the last two kinds of rock are found in the crust only, unless they are melted into lava. 

Example Question #7 : Soil Formation, Composition, And Properties

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?

Possible Answers:

O Horizon

C Horizon

A Horizon

B Horizon

R Horizon

Correct answer:

B Horizon

Explanation:

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.

Example Question #6 : Soil Formation, Composition, And Properties

Soil is stratified into different layers, called horizons. Which horizon contains freshly fallen leaves, plant litter, and lots of organic matter?

Possible Answers:

O Horizon

R Horizon

B Horizon

C Horizon

A Horizon

Correct answer:

O Horizon

Explanation:

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.

Example Question #7 : Soil Formation, Composition, And Properties

What are soil horizons?

Possible Answers:

The result of human disturbances

The physical properties of the soil

The horizontal layers of soils

The materials that make up the soil

The chemical properties of the soil

Correct answer:

The horizontal layers of soils

Explanation:

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. 

Example Question #10 : Soil Formation, Composition, And Properties

What is the brown insoluble particles from partially decomposed organic matter?

Possible Answers:

Clay

Waterlog

Humus

Minerals

Rill

Correct answer:

Humus

Explanation:

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.

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