1.
Soil is a mixture of weathered rock and ____________.
Correct Answer
D. All of the above
Explanation
The correct answer is "all of the above" because soil is indeed a mixture of weathered rock, water, air, and decayed organic matter. These components contribute to the composition and fertility of soil. Weathered rock provides the mineral fragments, water and air fill the spaces between the soil particles, and decayed organic matter adds nutrients and improves soil structure. Therefore, all of these elements are present in soil, making the answer "all of the above" correct.
2.
The layer of soil that contains the most humus and smaller rock and mineral particles than the other layers is the _____ horizon.
Correct Answer
A. A
Explanation
The correct answer is A. The A horizon is the top layer of soil, also known as the topsoil. It contains the most humus, which is organic matter that provides nutrients for plants, and smaller rock and mineral particles compared to the other layers. This layer is crucial for plant growth and supports a variety of organisms.
3.
All of the following are direct causes of mechanical weathering except__________.
Correct Answer
D. Oxygen
Explanation
Oxygen is not a direct cause of mechanical weathering. Mechanical weathering refers to the physical breakdown of rocks into smaller fragments without any chemical changes. Oxygen is not directly involved in this process. The other options - ice, tree roots, and water - are all examples of direct causes of mechanical weathering. Ice can cause rocks to crack and break apart when it expands in the cracks. Tree roots can grow into cracks and exert pressure, causing rocks to break. Water can enter cracks and freeze, expanding and breaking rocks apart.
4.
Over thousands of years, _________ has chemically weathered limestone, creating caves.
Correct Answer
B. Carbonic acid
Explanation
Carbonic acid is the correct answer because it is known to chemically weather limestone over thousands of years, leading to the formation of caves. Carbonic acid is formed when carbon dioxide dissolves in water, and it reacts with the calcium carbonate in limestone to form calcium bicarbonate, which is soluble and can be easily carried away by water. This process, known as carbonation, gradually erodes the limestone, creating cavities and caves over time.
5.
Chemical weathering is more rapid in a __________ climate.
Correct Answer
B. Tropical
Explanation
Chemical weathering is more rapid in a tropical climate because the warm temperatures and high humidity accelerate the chemical reactions that break down rocks and minerals. The combination of heat and moisture promotes the growth of vegetation, which produces organic acids that further enhance weathering. Additionally, the intense rainfall in tropical regions can lead to the leaching of minerals from the soil, contributing to the overall process of chemical weathering.
6.
Mechanical weathering is more rapid in a __________ climate.
Correct Answer
C. Cold
Explanation
Mechanical weathering refers to the physical breakdown of rocks into smaller fragments. Cold climates are characterized by freeze-thaw cycles, where water seeps into cracks in rocks, freezes, and expands, causing the rocks to break apart. This process is more rapid in cold climates because the repeated freezing and thawing accelerates the mechanical weathering process. In contrast, in dry, tropical, and moderate climates, there is less water available for this freeze-thaw process to occur, resulting in slower mechanical weathering.
7.
The organic material in humus includes _______________.
Correct Answer
A. Plant leaves and stems
Explanation
Humus is a dark, organic material that forms in soil when plant and animal matter decomposes. It is rich in nutrients and helps improve soil structure and fertility. The organic material in humus primarily comes from plant leaves and stems, as they break down and contribute to the formation of humus. Weathered rocks, sand, and air are not organic materials and do not contribute to the formation of humus.
8.
How fast weathering occurs depends on the _____________ of an area.
Correct Answer
B. Climate
Explanation
Weathering is the process by which rocks and minerals are broken down into smaller pieces. The speed at which weathering occurs is influenced by various factors, including climate. Climate refers to the long-term weather conditions of an area, such as temperature, humidity, and precipitation. Different climates have different weather patterns, which can affect the rate and type of weathering that takes place. For example, areas with high temperatures and frequent rainfall may experience more intense chemical weathering, while areas with freezing temperatures may have more mechanical weathering due to the expansion and contraction of water in cracks. Therefore, climate plays a significant role in determining the rate of weathering in an area.
9.
Compared to the A horizon in a soil profile, the B horizon ________________.
Correct Answer
D. All of these
Explanation
The B horizon in a soil profile is compared to the A horizon in multiple aspects. It is lighter in color, indicating a lower organic matter content. Additionally, the B horizon contains materials that have been leached from the A horizon, such as minerals and nutrients that have been washed down through the soil profile. As a result, the B horizon contains less humus, which is the organic component of soil. Therefore, all of these statements are true when comparing the B horizon to the A horizon in a soil profile.
10.
The difference between mechanical and chemical weathering is _________.
Correct Answer
C. Only one changes the chemical composition of a rock
Explanation
Mechanical weathering refers to the physical breakdown of rocks into smaller pieces without changing their chemical composition, while chemical weathering involves the alteration of the chemical composition of rocks. Therefore, the correct answer states that only chemical weathering changes the chemical composition of a rock.
11.
Causes of soil erosion include ____________.
Correct Answer
D. All of these
Explanation
Soil erosion can be caused by various factors, including wind, water, and the removal of vegetation. Wind can carry away loose soil particles, causing erosion in areas with strong winds. Water, such as rainfall or flowing rivers, can wash away soil particles and create channels or gullies. The removal of vegetation, such as deforestation or overgrazing, can leave the soil exposed and vulnerable to erosion by wind and water. Therefore, all of these factors contribute to soil erosion.
12.
Below the C horizon is ____________.
Correct Answer
C. Bedrock
Explanation
The C horizon is the layer of soil that lies beneath the B horizon. It is composed of weathered parent material and lacks the organic matter and nutrients found in the upper layers of soil. Below the C horizon is the bedrock, which is the solid rock layer that underlies all soil and is not affected by weathering or erosion.
13.
Which is formed by glacial erosion
Correct Answer
B. Moraines
Explanation
Moraines are formed by glacial erosion. Glaciers pick up rocks, soil, and debris as they move, and when the ice melts, it deposits this material in the form of moraines. Moraines can take different shapes and sizes, such as lateral moraines, which form along the sides of a glacier, or terminal moraines, which mark the furthest extent of a glacier's advance. These deposits provide important evidence of past glacial activity and can help scientists understand the history and behavior of glaciers.
14.
_____________ is the removal of minerals from the A horizon to the other horizons below by dissolving minerals with water.
Correct Answer
C. Leaching
Explanation
Leaching is the process of minerals being removed from the A horizon of soil and transported downwards to lower horizons through the dissolution of minerals with water. This occurs when water percolates through the soil, carrying dissolved minerals with it. Leaching is an important natural process that can impact soil fertility and nutrient availability.
15.
Which of these is not a cause of soil erosion?
Correct Answer
D. Planting trees
Explanation
Planting trees is not a cause of soil erosion because trees help to prevent erosion. Their roots hold the soil in place, reducing the impact of running water and wind. Additionally, the canopy of trees provides shade, which helps to slow down the evaporation of moisture from the soil, keeping it more stable. Therefore, planting trees can actually be a solution to combat soil erosion rather than a cause of it.
16.
____________ is the chemical process that occurs when iron is exposed to oxygen in the air.
Correct Answer
A. Oxidation
Explanation
Oxidation is the correct answer because it is the chemical process that occurs when iron is exposed to oxygen in the air. During oxidation, iron reacts with oxygen to form iron oxide, commonly known as rust. This process is accelerated in the presence of moisture.
17.
______ affects soil development because the longer the weathering has occured, the less the soil resembles the parent rock.
Correct Answer
D. Time
Explanation
The longer weathering occurs, the more time there is for physical and chemical processes to break down the parent rock into smaller particles. Over time, these particles mix with organic matter and minerals, forming soil. As weathering continues, the soil becomes more developed and less similar to the original parent rock. Therefore, time is the factor that affects soil development in this context.
18.
Small spaces between soil particles may be filled with ______ or ______ .
Correct Answer
A. Air or water
Explanation
Small spaces between soil particles may be filled with air or water. These spaces, also known as pores, exist in the soil and play a crucial role in supporting plant growth. The presence of air in the soil pores allows for the exchange of gases, such as oxygen and carbon dioxide, which are essential for root respiration. On the other hand, water-filled pores provide the necessary moisture for plants to absorb nutrients and maintain their hydration. Therefore, both air and water are important components that can occupy the small spaces between soil particles.
19.
A soil profile is made up of different __________.
Correct Answer
C. Layers
Explanation
A soil profile is made up of different layers. These layers are formed over time due to various factors such as weathering, erosion, and deposition. Each layer has its own unique characteristics, including different types of minerals, organic matter, and physical properties. These layers, also known as horizons, play a crucial role in determining the fertility and composition of the soil.