Assignment 5

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Dec 6, 2023

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Phillip Nguyen Assignment 5 Chapter 11 Review Questions: 1. What is the relationship between the degree of sorting of a sediment deposit and the range in particle size exhibited by the individual sediments? Are well-sorted sediments more likely to be found in continental margins or on the deep-ocean floor? Explain your answer. Answer: The degree of sorting in a sediment deposit is linked to the range in particle size exhibited by individual sediments. Well-sorted sediments are characterized by a narrow range in particle size, where most of the particles are of similar size. In contrast, poorly sorted sediments display a wide range of particle sizes, including both fine and coarse particles. Well-sorted sediments are more likely to be found on continental margins. This is because continental margins typically receive a mix of different sediments from various sources, including rivers, glaciers, and biogenous materials, leading to a broader range of particle sizes and poor sorting. In contrast, deep-ocean floors, far from land, primarily accumulate fine-grained lithogenous quartz grains and clay minerals due to limited biogenous activity and the extended time it takes for these particles to reach the ocean floor. These conditions result in well-sorted sediments with a narrower range of particle sizes. 3. What are the two most common types of biogenous sediment on the ocean floor? Answer: The two most common types of biogenous sediment found on the ocean floor, as per the information provided in the text, are calcareous oozes and siliceous oozes. Calcareous oozes are primarily composed of the hard parts of organisms like coccolithophores, pteropods, and foraminifera. These oozes accumulate in ocean waters shallower than the carbonate compensation depth (CCD), where calcium carbonate (CaCO3) skeletal and shell materials do not dissolve. Siliceous oozes, on the other hand, are composed of the skeletal and shell material of diatoms and radiolaria. Although silica in ocean water is under-saturated, areas with high surface productivity can suppress further silica dissolution, leading to the accumulation of siliceous oozes. These two biogenous sediment types are influenced by factors like ocean depth, chemistry, and nutrient availability, creating distinct distribution patterns across different oceanic regions. 5. Compare the locations and accumulation rates of neritic and pelagic ocean sediment deposits. Answer: Neritic and pelagic ocean sediment deposits, as discussed in the provided text, differ significantly in their locations and accumulation rates. Neritic deposits predominantly occur along continental margins, encompassing bays, wetlands, estuaries, beaches, and deltas. They primarily consist of coarse sediments transported by rivers, with approximately 95% of these sediments being trapped and deposited near the coast. In some cases, these sediments lead to the formation of deltas. These neritic deposits often have faster accumulation rates due to the

proximity of terrestrial sources. In contrast, pelagic deposits are deep-ocean sediments, and their accumulation rate is considerably slower. They primarily consist of fine-grained particles and form particle-by-particle on the deep-ocean floor. On average, it takes about 1,000 years to accumulate a 1-mm thick layer of pelagic sediment, whereas neritic deposits accumulate at a faster rate due to their proximity to land. Additionally, the type of pelagic deposits varies depending on factors like primary production, ocean depth, and chemistry, and they are primarily found beyond continental margins in the open ocean. 7. Why might it be uncommon to find carbonate ooze in the north central Pacific basin? Answer: Carbonate ooze is relatively uncommon in the north central Pacific basin due to specific environmental factors. The carbonate compensation depth (CCD), which marks the depth below which calcium carbonate (CaCO3) dissolves and does not accumulate, is relatively shallow in the Pacific Ocean, especially in the north central region. This is because the Pacific Ocean's deep waters are older, having higher concentrations of dissolved carbon dioxide, making calcium carbonate more soluble. As a result, calcareous organisms' shells and skeletons dissolve before they can accumulate as ooze. The Pacific Ocean's unique chemistry and the age of its deep waters contribute to the scarcity of carbonate ooze in the north central Pacific basin. Chapter 11 Critical Thinking questions: 1. What sequence of events could account for the presence of relatively coarse sediments on the deep-ocean floor? Answer: The presence of relatively coarse sediments on the deep-ocean floor can be explained by a sequence of events involving turbidity currents. These currents are initiated by various triggers like earthquake vibrations or sudden large discharges of sediments from rivers. Initially, sediments accumulate on the continental shelf and slope, particularly in areas where river channels are filled with sediment. When these sediments become unstable, they break loose and flow down the continental slope as turbidity currents, similar to land avalanches. As these turbidity currents gain momentum, they entrain more sediment and water, retaining larger particles in suspension. Upon reaching the abyssal plain, the currents slow down, causing sediment deposition in the order of particle size, resulting in graded beds or turbidite layers on the deep-ocean floor. This sequence of events accounts for the presence of coarser sediments in the deep-ocean. 3. How might a lower pH of ocean water affect the abundance of calcareous sediment that accumulates on the ocean floor? Answer: A lower pH of ocean water, which indicates increased acidity, can significantly impact the abundance of calcareous sediment accumulating on the ocean floor. As the pH decreases, the ocean water becomes more acidic, making it challenging for calcium carbonate (CaCO3) skeletons and shells from calcareous organisms to survive in the water column. The solubility of calcium carbonate increases in more acidic conditions. This higher solubility results in the dissolution of the calcareous material before it can accumulate on the ocean floor, particularly

below the carbonate compensation depth (CCD). Thus, a lower pH causes a reduction in the abundance of calcareous sediment, limiting its accumulation on the ocean floor. 5. What is the significance of the carbonate compensation depth (CCD)? How might ocean acidification affect the CCD? Answer: The carbonate compensation depth (CCD) is a crucial concept in oceanography because it represents the depth in the ocean below which calcium carbonate (CaCO3) skeletal and shell materials dissolve and do not accumulate on the ocean floor. The CCD is significant because it determines the limit at which calcareous oozes can accumulate. If the ocean becomes more acidic due to ocean acidification, the CCD becomes shallower. Ocean acidification is caused by increased carbon dioxide (CO2) concentrations, which make the water more acidic. The higher acidity leads to increased solubility of calcium carbonate, causing calcareous shells and skeletons to dissolve more readily. Consequently, ocean acidification shifts the CCD closer to the ocean's surface, making it more challenging for calcareous sediments to accumulate on the ocean floor, ultimately affecting the composition of sediments and the marine ecosystem. 7.What might the dominant sediment type along the eastern Pacific Ocean basin be? Explain. Answer: The dominant sediment type along the eastern Pacific Ocean basin is likely to be deep- ocean clays or "red clays." This expectation arises from the combination of factors described in the provided text. The Pacific Ocean's unique characteristics, such as the relatively deep ocean floor and the presence of older deep water with high dissolved carbon dioxide concentrations, result in a shallower carbonate compensation depth (CCD) compared to other ocean basins. As a result, calcareous particles dissolve more easily in the Pacific Ocean, making calcareous oozes less common. Deep-ocean clays, which consist predominantly of very fine-grained lithogenous material, are more likely to dominate the sediments in the eastern Pacific Ocean basin far from land. This geological and chemical environment favors the accumulation of these types of sediments in this region. Chapter 12 Review Questions: 1. Summarize the major lessons from the climate past. The major lessons we learned throughout the years would be natural climate variability: Earth's climate has naturally fluctuated over geological time scales due to factors like changes in Earth's orbit, solar radiation, and volcanic activity. Consequences of Rapid Changes: Rapid climate changes can have severe consequences for ecosystems and biodiversity, as evidenced by past mass extinctions. Greenhouse Gas Role: Greenhouse gases play a significant role in driving temperature changes, and the current rate of increase in CO2 is unprecedented. These lessons are essential for understanding and addressing contemporary climate challenges. 3. Describe major features of the current Holocene epoch.

The current Holocene epoch, as discussed in the chat, is characterized by several major features: Relative Climate Stability: The Holocene is marked by a relatively stable and mild climate compared to earlier epochs, with a relatively constant global mean temperature. Human Influence: Human activities, particularly agriculture and urbanization, have become dominant forces shaping the environment and climate during this epoch. Rising CO2 Levels: The Holocene has seen a notable increase in atmospheric CO2 concentrations, primarily due to human activities, resulting in enhanced greenhouse effect and global warming. These features highlight the significance of the Holocene epoch, especially in terms of its climate stability and the growing human impact on the Earth's systems. 5. Define global radiative equilibrium and describe its significance for Earth’s climate. Global radiative equilibrium refers to the balance between the incoming solar radiation absorbed by Earth and the outgoing thermal (infrared) radiation emitted by the planet. This equilibrium is significant for Earth's climate because it determines the planet's overall temperature. When Earth is in global radiative equilibrium, incoming solar energy matches the outgoing thermal radiation, leading to a relatively stable climate. Any disruptions in this equilibrium, such as an increase in greenhouse gases, can lead to an energy imbalance, causing global temperatures to rise, resulting in climate change and its associated consequences. Maintaining global radiative equilibrium is crucial for Earth's climate stability. 7. Describe the stability of the West Antarctic Ice Sheet and the East Antarctic Ice Sheet. The West Antarctic Ice Sheet (WAIS) is considered less stable than the East Antarctic Ice Sheet (EAIS). The WAIS is grounded on a bed that is well below sea level, making it vulnerable to the intrusion of warm ocean waters, which can lead to accelerated melting and ice loss. On the other hand, the EAIS is grounded above sea level, which provides more stability. However, recent research suggests that certain parts of the EAIS, particularly the Wilkes Subglacial Basin, may also be susceptible to instability due to its lower-lying bedrock. Chapter 12 Critical Thinking questions: 1. How are proxy climatic data sources used to reconstruct past climate conditions? Proxy climatic data sources are instrumental in reconstructing past climate conditions. They provide indirect evidence of past climates, such as tree rings, ice cores, sediment layers, and historical documents. By analyzing these proxies, scientists can infer information about temperature, precipitation, and other climate parameters. For example, tree rings offer insights into past temperatures, while ice cores provide records of past atmospheric conditions. Sediment layers in lakes and oceans contain information about past climates and can reveal changes in vegetation and ocean currents. Historical documents can provide anecdotal evidence of past climate events. These proxy data sources are valuable tools for understanding the Earth's climate history and how it has changed over time. 3. How does the thermal inertia of the ocean affect global climate change?

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