Geography Notes (PDF)

Geography notes Weathering is the process of breaking down rocks and soil due to the action of weather. There are three main types of weathering: physical, chemical, and biological weathering. 1. Physical Weathering: This includes processes like block separation and freeze-thaw action....

Geography notes Weathering is the process of breaking down rocks and soil due to the action of weather. There are three main types of weathering: physical, chemical, and biological weathering. 1. Physical Weathering: This includes processes like block separation and freeze-thaw action. In climates where temperatures vary greatly, such as the interior of South Africa (e.g., Paarl), water collects in rock cracks. When the weather is cold, the water freezes and expands, exerting pressure on the cracks. Over time, the crack widens and deepens, causing block separation. The cycle of freezing and thawing continues, eventually breaking the rock into smaller pieces. 2. Exfoliation: This type of physical weathering occurs in dry areas, especially where there is a significant difference between day and night temperatures. Rocks expand in the heat of the day and contract at night. In deserts, where temperature fluctuations can exceed 30°C, this constant expansion and contraction weaken the outer layers of rocks, causing large pieces to peel off in layers, similar to the peeling of an onion. 3. Chemical Weathering: This involves chemical reactions that break down rocks. One example is carbonation, where carbon dioxide in rain reacts with rocks containing calcium carbonate, such as limestone. The rain forms a weak acid called carbonic acid, which dissolves calcium carbonate into calcium bicarbonate, which is soluble in water. In colder climates, rainwater absorbs more carbon dioxide, making the carbonic acid stronger. Oxidation is another form of chemical weathering, where oxygen in water reacts with iron-rich rocks, forming iron oxide (rust), which weakens the rock. Hydrolysis is a chemical reaction where water interacts with silicate minerals (like those in granite and sandstone), transforming them into clay, which is soluble and easily washed away. 4. Biological Weathering: This occurs due to the activities of living organisms, including plants and animals. For example, tree roots can penetrate small cracks in rocks, eventually breaking them apart. Lichens, a type of plant, secrete acids that break down minerals in rocks, causing them to loosen and crumble. Animals like worms and moles burrow in the soil, exposing rocks to further weathering. Erosion and River Processes Erosion is the transportation of weathered material, and deposition occurs when the transporting agent (water, wind, or ice) loses its energy and drops the material it is carrying. Rivers: In the upper course, rivers have a steep gradient and flow faster, eroding their bed and banks. This erodes the river’s load, and larger rocks and boulders are transported. Over time, this leads to the formation of deep V-shaped valleys and may cause the formation of waterfalls. Waterfalls form where harder rock overlays softer rock. The river erodes the soft rock beneath, and the overhanging harder rock eventually breaks off, creating a plunge pool below. Over time, the waterfall retreats upstream. Rapids: Rapids occur in areas where hard, erosion-resistant rocks alternate with soft rocks, leading to a more turbulent river flow. The soft rock erodes quickly, while the resistant rock remains exposed, creating rapids. Rapids attract tourists, and examples include whitewater rafting on the Orange River. Gorges and Canyons: A gorge is a steep-sided valley typically formed in a humid climate. In contrast, a canyon forms in areas with dry climates. Gorges tend to be straighter, while canyons are usually wider and deeper, often caused by increased downward erosion. In the middle course of a river, lateral erosion occurs, widening the river channel. As the gradient decreases, the river’s speed slows down, leading to the formation of meanders. Meanders form due to both erosion on the outside of the bend (where the river flows faster) and deposition on the inside of the bend (where the river flows more slowly). Over time, meanders migrate, and the neck of the meander narrows. Eventually, a meander can be cut off by flooding, forming an oxbow lake. In the lower course, the river gradient is almost flat, and the river’s velocity and erosive power decrease. Deposition becomes dominant, and features such as levees and deltas form. Levees are natural mounds on the riverbanks created by flooding, while deltas form where a river meets a larger body of water, causing the river to slow down and deposit its load. Over time, the delta grows and forms a triangular shape. Soil Erosion and Agriculture Soil erosion occurs when soil is removed from the land faster than it can be replaced. Vegetation helps protect soil by binding it together, and when vegetation is removed, the soil becomes exposed and is more easily eroded. The removal of vegetation, particularly through deforestation, agriculture, and construction, increases surface runoff and decreases the infiltration of water into the soil. This leads to soil degradation and desertification. Soil that is eroded and deposited in rivers reduces water quality, causes siltation (which shallows the riverbed), and may lead to flooding. Exposed soil is prone to being blown away by wind or washed away by rain. Factory Farming and Food Security Factory farming, also known as concentrated animal feeding operations (CAFOs), uses industrial methods to raise large numbers of animals in confined spaces. This system is designed to maximize profits but often results in significant environmental damage, including soil erosion and water pollution. The crowded conditions also harm the welfare of the animals, which are raised to grow quickly with little room to move. Despite agricultural advancements, food insecurity remains a global issue. Solutions to food insecurity include the use of genetically modified (GMO) crops, precision farming techniques, and food preservation methods like refrigeration, freezing, and canning, which increase food availability and reduce spoilage. Technology, such as weather apps, has also improved agricultural production and sustainability. Here is a study guide that covers the topics outlined in your exam: WEATHERING, EROSION, AND DEPOSITION (35 MARKS) QUESTION 1: Concepts of Weathering, Erosion, and Deposition  1. Definitions: Weathering: The breakdown of rocks and soil due to environmental conditions, without significant movement. Erosion: The movement or transportation of weathered material by water, wind, or ice. Deposition: The laying down of eroded material when the transporting agent loses energy. 2. Types of Weathering: Chemical Weathering: Breakdown of rocks through chemical reactions (e.g., carbonation, oxidation, hydrolysis). Physical Weathering: Breakdown through physical forces (e.g., freeze-thaw, exfoliation). Biological Weathering: Caused by living organisms, like roots breaking rocks or acids from lichens. 3. Impact of Human Activities on Weathering: Digging, Farming, and Deforestation: Expose rocks to weathering. Construction and Irrigation: Increase soil erosion and alter natural weathering processes. Pollution: Increases acid rain, which accelerates chemical weathering. Concepts and Features of Erosion and Deposition in Rivers 1. Upper Course: Steep Gradient: High energy, causing vertical erosion. Features: V-shaped valleys, waterfalls, rapids, and gorges. 2. Middle Course: Lateral Erosion: Widens the river channel. Features: Meanders form as erosion occurs on the outer banks and deposition on the inner banks. 3. Lower Course: Gentle Gradient: Low energy, leading to deposition. Features: Wide, U-shaped valleys, levees, and deltas. Soil Erosion Definition: The removal of soil by water, wind, or human activities. Impacts: Loss of fertile land, water pollution, and reduced water storage in rivers. Human Impact: Increased by activities like deforestation, farming, and construction. RESOURCES AND SUSTAINABILITY (40 MARKS) QUESTION 2: Concepts of Resources and Sustainability 1. Types of Resources: Non-Renewable: Resources that cannot be replenished (e.g., coal, oil). Renewable: Resources that naturally replenish over time (e.g., wind, solar).  Perpetual: Resources that are inexhaustible (e.g., sunlight). 2. Effects of Unwise Use of Resources: Environmental Degradation: Pollution, loss of biodiversity. Resource Scarcity: Depletion of essential resources (e.g., water). Climate Change: Increased greenhouse gas emissions from overuse of fossil fuels. 3. Overfishing and Sustainable Fishing: Overfishing: Leads to depletion of fish stocks and disrupts marine ecosystems. Sustainable Fishing: Using methods that allow fish populations to replenish, such as catch limits. 4. Overgrazing, Factory Farming, and Sustainable Grazing/Farming: Overgrazing: Destroys vegetation and leads to soil erosion. Factory Farming: Intensive livestock production that often harms animal welfare and the environment. Sustainable Grazing and Farming: Practices that protect soil health, biodiversity, and animal welfare. 5. Deforestation: Impacts: Loss of biodiversity, increased carbon dioxide, and soil erosion. Solutions: Reforestation, sustainable forestry practices. 6. Food Security and Food Insecurity: Food Security: Reliable access to sufficient, nutritious food. Food Insecurity: Lack of reliable access to food. Improvement Strategies: Sustainable agriculture, reducing food waste, and supporting local food systems. 7. Role of the Consumer/Individual and Government/Business in Reducing Carbon Footprint: Consumer Actions: Choosing sustainable products, reducing waste, conserving energy. Government and Business Actions: Implementing policies for renewable energy, reducing emissions, and supporting sustainable development. This guide condenses the key concepts from your study material. Let me know if you need any further details on any topic!