Weathering and Erosion
If a rock particle is loosened, chemically or mechanically, but remains there itself, it is called weathering. Once the rock particle starts moving by agents such as water, snow, wind, waves and gravity, it is known as erosion.
What is Weathering?
Weathering is the process of breaking down of rocks, soil and minerals as well as artificial materialsthrough contact with the atmosphere, biological life and waters. There are two kinds of weathering: physical and chemical weathering. Mechanical or physical weathering takes place by the breakdown of rocks and soils through direct contact with atmospheric surroundings, such as heat, water, ice and pressure.
Chemical weathering involves the direct effect of chemicals present in atmosphere or biologically produced chemicals in the breakdown of rocks, soils and minerals. The physical weathering take place in very cold or very dry environments, whereas the chemical weathering occurs where the climate is wet and hot.
In fact, both types of weathering happen together, and each facilitate one another. For instance, physical abrasion reduces the size of particles and hence increases their surface area, which makes them more prone to rapid chemical reactions. The different agents work in coordination to transform primary minerals such as feldspars and micas into secondary minerals like clays and carbonates, and discharge plant nutrient elements in soluble forms. Various Earth’s landscapes and landforms are the result of weathering processes in association with erosion.
What is Erosion?
Erosion is the action of exogenous processes which remove soil and rock from one location and transport it to another location where it is deposited. The eroded sediment can be transported to just a few millimeters, or even to some thousands of kilometers. Although erosion is a natural process, but human activities have increased tremendously the rate at which erosion is occurring on this planet. Accelerated erosion causes both onsite and offsite problems.
Examples of on-site impacts are reduction in agricultural productivity and ecological collapse, both being the result of the loss of the nutrients from upper soil layers. In extreme cases, this leads to desertification also. Examples of off-site impacts include sedimentation of waterways and eutrophication of lakes and ponds. Water and wind erosion together are responsible for approximately 84% of the land degradation on the globe.