Which of the following statements about horizons is true? a. They are characterized by whether they are solid, liquid, or gas. b. They are represented by Roman numerals. c. All soils have completely different horizon patterns. d. They are defined by their different physical features. Please select the best answer from the choices provided OOO
The Correct Answer and Explanation is:
Correct Answer: d. They are defined by their different physical features.
Explanation
Soil horizons are layers of soil that form through the processes of soil formation (pedogenesis). These horizons are typically arranged in a vertical sequence, forming what is known as a soil profile. Each horizon has distinct characteristics that differentiate it from the others, primarily based on physical and chemical features such as color, texture, structure, and composition.
Option d is correct because soil horizons are defined by their different physical features, including the amount of organic matter, mineral content, particle size, and moisture. For example, the O horizon is rich in organic material, the A horizon (topsoil) is a mixture of organic material with minerals, and the B horizon (subsoil) typically accumulates materials like clay, iron, or aluminum leached down from upper layers.
Option a is incorrect because soil horizons are not categorized by being solid, liquid, or gas. While water and air content can vary within a soil profile, horizons are defined primarily by composition and structure rather than state of matter.
Option b is incorrect because soil horizons are not represented by Roman numerals. Instead, they are usually designated by letters such as O, A, E, B, C, and R, each representing a specific type of horizon. For instance, the R horizon refers to unweathered bedrock.
Option c is incorrect because while soils can vary significantly depending on environmental factors like climate, parent material, and biological activity, there is a general pattern of horizon development that can be seen across different soils. Not all soils have completely different horizon patterns; many share similar layers (such as A, B, and C) but with variations in thickness, color, and texture.
In summary, soil horizons are best understood as layers defined by physical characteristics that develop over time through natural processes, making option d the most accurate and scientifically supported statement.
