1a. With equations, explain (¡) Oxidation and (¡¡) Dehydration
b. How does (1) rock type (ii) slope (iii) climate influence weathering?
c. Explain how (i) geological factor and (ii) over grazing cause erosion
a.
(i) Oxidation: Oxidation is a chemical reaction that occurs when a substance loses electrons. In terms of oxidation in the context of weathering, it refers to the reaction of minerals or rocks with oxygen. This process is commonly seen in iron-rich minerals like pyrite (FeS2), where the iron reacts with oxygen to form iron oxide (Fe2O3). Some common signs of oxidation are the reddish coloration of rocks, known as rust, or the weathered appearance of minerals.
(ii) Dehydration: Dehydration refers to the removal of water molecules from a substance. In the context of weathering, dehydration can occur when water is removed from minerals or rocks, causing them to shrink or crack. This process is often seen in clay minerals, which can expand when they absorb water and contract when they lose it. Dehydration can lead to the weakening and disintegration of rocks.
b.
(i) Rock type: The type of rock influences weathering because different rocks have varying susceptibility to mechanical and chemical weathering processes. For example, igneous rocks like granite tend to be more resistant to weathering due to their crystalline structure, while sedimentary rocks like limestone are more prone to dissolution by acidic water. The mineral composition, porosity, and permeability of rocks also impact their weathering rates.
(ii) Slope: Slope steepness affects weathering by influencing the amount of water runoff and the exposure to physical weathering processes. Steep slopes generally have faster water runoff, which limits the contact time between water and rocks, potentially reducing weathering rates. However, they may also experience more intense mechanical weathering due to the force of gravity on rock fragments, leading to increased erosion and mass wasting.
(iii) Climate: Climate plays a significant role in weathering. Areas with high precipitation and warm temperatures tend to have more intense weathering due to the increased availability of water and the chemical reactions facilitated by heat. Freeze-thaw cycles in cold regions with seasonal freezing can also contribute to mechanical weathering. Additionally, climate affects the presence of vegetation, which can influence weathering processes by providing organic acids, stabilizing soils, and impacting the rates of erosion.
c.
(i) Geological factors: Geological factors are responsible for erosion as they determine the characteristics of the landscape, including the presence and type of rocks, soil composition, and surface features. The resistance of rocks to weathering and erosion, their inclination, and the presence of fractures or faults all influence erosion processes. For example, softer rocks will erode faster than harder ones, and a steep slope can enhance the speed of erosion due to gravity.
(ii) Overgrazing: Overgrazing occurs when there is excessive grazing of vegetation by livestock, leading to the removal or destruction of plants. This can cause erosion as plants play a crucial role in stabilizing the soil and preventing it from being washed away by rain or wind. When vegetation cover is reduced, the soil becomes more susceptible to erosion by water runoff and wind. Overgrazing can also lead to compaction of the soil, reducing its ability to absorb water and increasing surface runoff.