Geology 1403 Exam 2

Abundant moisture and warm temperatures create ideal conditions for chemical weathering processes to occur at a higher rate. Moisture allows for the dissolution and transport of minerals, while warm temperatures accelerate the chemical reactions involved in weathering. Therefore, it is true that abundant moisture and warm temperatures lead to high rates of chemical weathering.

Feldspars are a group of minerals that are commonly found in rocks. During the process of weathering, which involves the breakdown of rocks due to exposure to the elements, feldspars can decompose. This decomposition leads to the formation of clay minerals, silica, and soluble constituents. Therefore, the statement that feldspars commonly decompose during weathering to clay minerals, silica, and soluble constituents is true.

Chemical weathering refers to the breakdown and alteration of rocks through chemical processes. Bedrock, which is the solid rock beneath the soil and sediment layers, can undergo chemical weathering. Joints and sheeting fractures are common features in bedrock that provide pathways for water and chemicals to penetrate. These openings allow for increased surface area and exposure of the rock to chemical reactions, leading to the initiation of chemical weathering. Therefore, the statement that chemical weathering in bedrock below the land surface often begins along joints and sheeting fractures is true.

Very fine-grained iron oxide particles are responsible for the majority of red, yellow, and brown soil colors. Iron oxide, also known as rust, is a common mineral found in soil. These particles are small enough to be suspended in the soil and give it its characteristic colors. Therefore, it is true that very fine-grained iron oxide particles account for nearly all red, yellow, and brown soil colors.

Leaching is the process of removing soluble chemical constituents from the soil. This occurs when water carries these substances downward through the soil profile, away from the root zone. Therefore, the statement that removal of soluble chemical constituents from a soil is termed leaching is true.

Calcite, a major component of some monumental and building stones, slowly dissolves in weakly acidic waters. This means that over time, when exposed to weakly acidic water, calcite will gradually break down and dissolve. Therefore, the statement "Calcite, a major component of some monumental and building stones, slowly dissolves in weakly acidic waters" is true.

Sheeting is indeed mainly a process of mechanical weathering. Mechanical weathering refers to the physical breakdown of rocks into smaller pieces without any change in their chemical composition. Sheeting occurs when rocks that were formed under high pressure deep within the Earth's crust are exposed to the surface due to erosion. As these rocks are exposed to the lower pressure at the surface, they expand and crack, resulting in the outer layers of the rock peeling away in thin sheets. This process is known as sheeting and is a form of mechanical weathering.

Quartz being resistant to weathering means that it can withstand the effects of weather and erosion over time. This quality makes it a prominent component of sands found in riverbeds and on beaches, as these environments are constantly exposed to weathering forces. Therefore, the statement that quartz is resistant to weathering and is an important component of sands in riverbeds and on beaches is true.

Water is one of the few exceptions where it actually expands when it freezes. This is because the water molecules form a crystalline structure when they freeze, which takes up more space than the liquid form. This expansion is why ice floats on water, as the solid form is less dense than the liquid form.

Clay minerals formed from gabbro or diorite bedrock illustrate chemical weathering. Chemical weathering refers to the breakdown of rocks and minerals through chemical reactions. In this case, the minerals in the bedrock are being altered and transformed into clay minerals through chemical processes. This type of weathering typically occurs when water or other substances react with the minerals in the rock, causing them to dissolve or undergo chemical changes.

The statement suggests that the expectation or anticipation of iron is a significant chemical weathering process for minerals such as olivine and biotite, which are ferromagnesian silicates. This implies that iron plays a crucial role in the weathering of these minerals. Therefore, the correct answer is "True."

The correct answer is "areas of severe wind erosion on the Great Plains, 1930s." This best describes the Dust Bowl, which was a period of severe dust storms that occurred during the 1930s in the United States, primarily affecting the Great Plains region. The combination of drought, poor farming practices, and strong winds led to the erosion of topsoil and the creation of massive dust storms that devastated agriculture and caused significant economic and environmental damage.

In a cool, temperate forest soil, the humus layer is typically thicker because although less humus is produced, the rate of decay and oxidation is slower compared to a tropical rainforest soil. This means that the organic matter in the cool, temperate forest soil takes longer to break down, leading to a buildup of humus over time. In contrast, in a tropical rainforest, more humus may be produced, but it is quickly washed away by the heavy rains, preventing the formation of a thick humus layer.

Frost wedging is a weathering process in which water seeps into cracks in rocks, freezes, and expands, causing the rocks to break apart. This process is particularly effective in cold climates with freeze-thaw cycles. Talus slopes are formed by the accumulation of broken rock fragments at the base of steep slopes or cliffs, often as a result of frost wedging. Therefore, talus slopes are the regolith material formed by the major weathering process of frost wedging.

The correct order of the different soil horizons from the land surface downward to the unweathered bedrock is 0, A, E, B, C, bedrock. This order follows the typical arrangement of soil horizons, starting with the organic matter-rich surface horizon (0), followed by the topsoil horizon (A), the leaching horizon (E), the subsoil horizon (B), the parent material horizon (C), and finally the unweathered bedrock.

The term "residual" describes a soil formed by the weathering of the underlying bedrock. This means that the soil is derived from the same material as the bedrock and has not been transported or moved from its original location. The weathering process breaks down the bedrock into smaller particles, creating the residual soil. This type of soil is often found in areas where the bedrock is exposed or close to the surface.

Sheeting fractures and exfoliation domes are geological features that occur in areas with soft, highly fractured bedrock. Sheeting fractures are parallel fractures that form due to the release of pressure on the rock surface, causing it to expand and crack. Exfoliation domes, on the other hand, are large, rounded rock formations that result from the removal of overlying rock layers, exposing the underlying bedrock. These features are commonly found in areas with soft and fractured bedrock because the rock is more susceptible to weathering and erosion, leading to the development of sheeting fractures and exfoliation domes. Therefore, the statement is true.

Warm temperatures and high levels of moisture can speed up rates of chemical reactions and weathering in rocks and soils. This is because warm temperatures increase the kinetic energy of molecules, making them more likely to react with each other. Additionally, moisture can act as a solvent, allowing for the dissolution of minerals and the transport of ions. Together, these factors promote the breakdown and alteration of rocks and minerals, leading to faster rates of chemical reactions and weathering.

Frost wedging is an important mechanical weathering process that occurs when water seeps into cracks and freezes, expanding and enlarging the cracks. This process is especially effective in colder climates where temperatures frequently fluctuate above and below freezing. As the water freezes and expands, it exerts pressure on the surrounding rock, causing it to fracture and break apart. Over time, this repeated freezing and thawing can extend the fractures deeper into large boulders and bedrock, eventually breaking them down into smaller pieces.

Sheeting fractures best describe sets of fractures in relatively fresh bedrock, such as granite, that are roughly parallel to the land surface. Sheeting fractures are caused by the release of pressure as overlying rocks are eroded and removed, resulting in the outer layers of the rock peeling away in parallel sheets. This process is commonly observed in granite and other igneous rocks, and it creates fractures that are parallel to the land surface.

Mechanical weathering refers to the physical breakdown of rocks into smaller particles without any change in their chemical composition. It includes processes like frost wedging, thermal expansion, and abrasion. Therefore, the statement "involves a major change in the mineral composition of the weathered material" is not true because mechanical weathering does not alter the mineral composition of the rocks, it only breaks them into smaller pieces.

The finely divided, red, brown, and yellow soil-coloring minerals originate by the precipitation of iron oxides during the chemical weathering process. This means that as the minerals in the soil undergo chemical weathering, iron oxides are formed and precipitate out, giving the soil its characteristic colors.

The correct answer is apples because planting grass between the trees helps to prevent soil erosion on steep hill slopes. The grass acts as a natural barrier, holding the soil in place and reducing the risk of erosion caused by water runoff. By not cultivating the land between the trees, the soil structure is maintained, further preventing erosion. This technique helps to maintain the stability of the soil and minimize the loss of topsoil on steep slopes.

When water freezes, it undergoes a phase change from a liquid to a solid state. During this phase change, the water molecules arrange themselves in a crystalline structure, causing the volume of the water to increase. As a result, the water expands as it freezes, exerting pressure on the crack walls and pushing them apart. This phenomenon is known as ice expansion and is responsible for the formation and widening of cracks in rocks due to repeated cycles of freezing and melting.

Erosion refers to the process by which weathered rock and mineral particles are removed from one area and transported. This involves the movement of these particles through various agents such as water, wind, or ice. Erosion plays a crucial role in shaping the Earth's surface over time, as it can create valleys, canyons, and other landforms. It is an ongoing process that continuously changes the landscape.

In the formation of a pedalfer soil, iron oxides and aluminum-rich clays are precipitated in the B-horizon. This process is known as illuviation, where minerals and materials are transported downward into the soil profile. As water percolates through the soil, it carries dissolved iron and aluminum compounds from the upper layers and deposits them in the B-horizon. This accumulation of iron oxides and aluminum-rich clays gives pedalfer soils their characteristic reddish or yellowish color.

Humus is a concentration of decaying organic matter in the B-horizons of lateritic soils. This statement is false because humus is actually a concentration of organic matter found in the topsoil layer, not in the B-horizons. The B-horizons of lateritic soils are typically characterized by the accumulation of minerals, not organic matter.

Quartz does not weather readily to aluminum-rich clav minerals.

The correct answer is chemical weathering of orthoclase feldspar. This is because clay minerals, silica (SiO2), and dissolved potassium bicarbonate in the soil water are commonly produced through the chemical weathering of orthoclase feldspar. Orthoclase feldspar is a common mineral found in granite and other igneous rocks, and it undergoes chemical reactions with water and other substances in the environment to break down and form these products. This process is a key component of the overall weathering and erosion of rocks.

North-facing slopes typically receive about the same amount of precipitation as south-facing slopes, but less moisture evaporates from north-facing slopes. This explains why north-facing slopes in the Rocky Mountain region of the United States are typically more moist and heavily forested than south-facing slopes. The moisture from precipitation is retained on the north-facing slopes due to less evaporation, creating a more favorable environment for trees and vegetation to thrive.

The unfractured interior of an angular fracture-bounded granitic block shows the highest rate of weathering. This is because the unfractured interior is more exposed to the elements and has a larger surface area compared to the edges, corners, and crack surfaces. The weathering process, which involves the breakdown of rocks due to physical, chemical, and biological processes, is accelerated in areas with more surface area and exposure to environmental factors. Therefore, the unfractured interior experiences a higher rate of weathering compared to other parts of the block.