Question

What is a mixture of rock and mineral fragments, organic matter, air, and water called? A) soil C) horizon B) limestone D) clay

Short answer

It's soil.

Step-by-step solution

Identifying the Question

The question is asking for a term that describes a mixture that includes rock and mineral fragments, organic matter, air, and water.

Understanding Key Terms

Let's analyze each option: - **Soil**: A natural body that includes organic matter, rock and mineral fragments, air, and water. - **Horizon**: A layer of soil distinct in color and texture, part of a soil profile. - **Limestone**: A sedimentary rock mainly composed of calcite. - **Clay**: A natural, malleable, fine-grained earth material that becomes plastic when wet.

Evaluating Option A

The definition of soil encompasses all components mentioned in the question: rock fragments, mineral fragments, organic matter, air, and water.

Evaluating Option B

Limestone is a type of rock and does not typically contain organic matter, air, or water in the way that is described in the question.

Evaluating Option C

A horizon refers to a specific layer within the soil and does not describe a mixture of the components in the same way the question asks.

Evaluating Option D

Clay is a type of soil component but does not encompass the full range of materials (like organic matter and air) mentioned in the question.

Conclusion

Given that only option A, "soil," fully matches the description of being a mixture of rock and mineral fragments, organic matter, air, and water, it is the correct answer.

Key concepts

Rock and Mineral Fragments

Rocks and minerals form the basic structure of soil. They are the skeleton that supports other soil components. These fragments are created through the processes of weathering and erosion. Over time, larger rocks break down into smaller pieces. This can happen due to:

• Water and Wind: These elements wear away rock surfaces.
• Temperature Changes: Expansion and contraction can cause cracking.
• Biological Activity: Roots can grow into cracks, breaking rocks apart.

These fragments vary greatly in size, ranging from large gravel pieces to tiny mineral particles like sand, silt, and clay. As these fragments mix with other components, they form the soil's texture, influencing drainage and how nutrients are held.

Organic Matter

Organic matter is a crucial ingredient in soil, derived from decomposed plants and animals. It is rich in nutrients, providing food for microorganisms that live in the soil. This component plays several key roles:

• Nutrient Supply: It enriches the soil with nitrogen, phosphorus, and sulfur.
• Soil Structure: Organic matter binds soil particles together, improving soil stability.
• Moisture Retention: It increases the soil's capacity to hold water.

As organic matter decays, it releases nutrients slowly, acting like a natural fertilizer. This makes it an essential component in maintaining healthy, fertile soil. Without organic matter, soil would lose much of its productivity.

Soil Composition

The composition of soil is complex, involving a mix of several components. It includes:

• Rock and Mineral Fragments: Provide the basic structure.
• Organic Matter: Supplies nutrients and improves texture.
• Air: Occupies pore spaces, vital for root respiration and microorganism survival.
• Water: Acts as a solvent and carrier for nutrients, essential for plant growth.

This mix is not static. The proportions of each component can change, altering the soil's properties. For example, heavy rainfall might increase water content or erosion might change the mineral balance. Each of these elements plays a vital role in supporting plant life and natural ecosystems.

Soil Science

Soil science is the study of soil as a natural resource. It examines the formation, classification, and mapping of soils. Understanding soil science is key for activities such as agriculture, forestry, and environmental management. Scientists in this field focus on areas such as:

• Soil Fertility: Investigating how soil supports plant growth.
• Soil Conservation: Developing practices to prevent soil erosion.
• Soil Classification: Categorizing soil types based on their characteristics.

By analyzing soil properties, scientists can predict how it will behave under different conditions, helping to improve crop yields and preserve natural habitats. This knowledge supports the sustainable use and management of soil resources around the world.