- Background Information
Erosion is a geological process in which Earth’s surface materials, such as soil, rock, and sediment, are worn away and transported by natural forces like water, wind, or ice (National Geographic, 2022). Water and ice, particularly glaciers, are the most common agents of erosion. When wind carries dust or when glacial ice and water carry mud, erosion occurs. The brown coloration often seen in eroded water or ice indicates the presence of soil and rock particles suspended and transported from one place to another. These transported materials are referred to as sediment. Liquid water is the most significant driver of erosion on Earth’s surface, as rain, rivers, floods, and ocean currents gradually carry away sand and soil, moving sediments over time (National Geographic, 2024).
Erosion has profound effects on landscapes, including the formation of oxbow lakes. According to National Geographic (2023), oxbow lakes form when erosion and soil deposition cause a river to cut across a narrow section of land at the bend of a meander, creating a shortcut. This process leaves behind a U-shaped lake, a remnant of the river’s previous course. Oxbow lakes typically contain still water, with no significant inflow or outflow, as they are no longer connected to the main river. Without a direct water source like a spring or stream, these lakes can gradually become bogs or swamps (National Geographic, 2024).
a. Activity
Coastal Erosion Ocean Science Experiment
1. In this experiment, a baking pan, water, and sand are used to simulate coastal erosion. Begin by piling sand on one end of the baking pan and pressing it down firmly to create a gradually sloping beach.
2. Slowly pour a small amount of water into the baking pan until the sand is partially submerged.
3. Gently tilt the pan back and forth to simulate wave action, creating movement on the “beach.”
4. Observe how the sand shifts and erodes due to the wave-like motion created by tilting the pan.
Variation: Testing the Effect of Vegetation on Erosion
5. Repeat the setup, but this time embed small tree fibers into the sand to simulate the presence of plant roots, which help stabilize the soil.
6. Perform steps 2-4 again and compare the difference in erosion with and without the “roots.”
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Case Study: Rock Weathering with Water and Time (Japanese Experiment)
In a study focused on the weathering of granite, researchers simulated natural conditions by exposing granite to water over time. The experiment demonstrated both chemical and physical weathering processes. The granite developed cracks, fissures, and surface degradation, with the most significant damage occurring in areas rich in feldspar, a key mineral in granite. Feldspar undergoes hydrolysis, breaking down into clay minerals when exposed to water, which accelerates the weathering process. This experiment showed how prolonged water exposure can degrade rocks, particularly in mineral zones vulnerable to chemical alteration.
The Future: Shoreline Protection
Shoreline hardening is a key strategy to prevent coastal erosion and weathering. Structures such as groins, seawalls, levees, and rip-raps are commonly used to protect coastlines from erosion caused by water currents, flooding, and storm surges. These structures help redirect or absorb wave energy, minimizing erosion impact. Additionally, beach nourishment, the process of adding sand to eroding beaches, serves as a buffer, helping to protect against future erosion (US Climate Resilience Toolkit, 2017).
Activity 2: How Erosion Varies by Soil Type
A. Gravel:
Gravel is highly resistant to erosion due to its large, coarse particles, which do not compact easily or allow much water infiltration. The heavier particles are less likely to be carried away by wind or water. However, in extreme conditions like heavy storms or flooding, streams can move gravel down slopes.
B. Sand:
Sand is more prone to erosion because its fine, loose particles do not bind together well. Wind erosion can displace sand particles, causing desertification or dune formation. Water erosion is particularly severe on sandy soils, especially during storms, which can wash away large volumes of sand, such as along coastal beaches.
C. Dirt (Loam, Clay, and Organic Matter):
Dirt consists of various soil types, including loam, clay, and organic matter, with moderate erosion susceptibility. Loamy soils, which contain a balance of sand, silt, and clay, resist erosion better due to their structure and ability to retain water. Clay soils are cohesive and more resistant to water erosion but can crack under dry conditions, making them vulnerable to wind erosion. Uncovered dirt, especially in heavy rain or wind-prone areas, is highly susceptible to erosion.
Preventing Erosion in the Future
Erosion can be mitigated through methods such as mulching, terracing, and increasing vegetation cover. Vegetation is one of the most effective ways to prevent erosion. Plant roots bind soil particles, reducing the likelihood of wind or water displacement. Trees, grasses, and shrubs can stabilize soil on slopes and erosion-prone areas by slowing down water runoff, allowing more time for water to infiltrate the soil.
Terracing is another method, particularly effective in hilly or mountainous regions. It reduces the speed of water runoff on slopes, minimizing erosion. Mulching involves applying a protective layer of organic or inorganic materials (such as straw, wood chips, or synthetic fabrics) over soil to shield it from direct rainfall. This helps reduce the impact of raindrops, which can disturb soil particles, and improves moisture retention, strengthening the soil structure and reducing erosion risk.
References
National Geographic. (2022, June 7). Erosion. National Geographic. https://education.nationalgeographic.org/resource/erosion/
National Geographic. (2023). oxbow lake. Education.nationalgeographic.org. https://education.nationalgeographic.org/resource/oxbow-lake/
National Geographic. (2024). Sediment | National Geographic Society. Education.nationalgeographic.org. https://education.nationalgeographic.org/resource/sediment/
U.S Climate Resilience Toolkit. (2017). Coastal Erosion | U.S. Climate Resilience Toolkit. Climate.gov. https://toolkit.climate.gov/topics/coastal-flood-risk/coastal-erosion#:~:text=Increases%20in%20storm%20frequency%20and
