Physical changes to the Earth’s surface caused by alterations in its atmosphere are known under the umbrella term of weathering (Bland & Rolls, 2016). The study of weathering, its nature, and effects can help to understand how these changes occur, how they can be controlled, and what impact they have on the environment. Thus, current environmental issues can be addressed and managed appropriately.
Weathering can come in several forms depending on its source and the effect that it produces. As a rule, mechanical, organic, and chemical weathering are singled out as the key types of the specified process. Having different causes, the phenomena mentioned above lead to different outcomes, such as the disintegration of minerals and the production of new ones.
Mechanical weathering, which is also defined as a physical one, implies decomposition of rocks in a particular area under the influence of mechanical forces. Since the latter can be produced either by natural phenomena such as wind, rain, and solar energy, or by the activities of living organisms, mechanical weathering is often conflated with the organic one. However, drawing a distinct line between the nature of causes is crucial for the further management of environmental issues, which is why most scholars prefer to restrict the concept of mechanical weathering to the effects of inanimate objects (Eppes & Keanini, 2017).
Organic weathering, also termed as biological, involves the disintegration of minerals with the help of living organisms. The specified phenomenon occurs as small organisms secrete acids that affect the structure of rocks, causing changes in their form and sometimes their composition (Ahluwalia, 2017).
For example, the roots of the plants that grow close to a mineral produce the acid that may cause the mineral to crack or even be destroyed. In addition, larger animals produce droppings that contain chemicals causing the father changes in the composition and form of rocks. Finally, burrowing animals may move rocks, making water trickle underneath. The following change in the position or temperature of rocks affects them significantly, causing their destruction.
Chemical weathering occurs once rocks decompose as a result of a chemical reaction. As a rule, the specified phenomenon takes place while oxygen, water, or both affect rocks continuously. Chemical weathering may also imply significant alterations in the composition of minerals (Ahluwalia, 2017). Specifically, during the process of chemical weathering, minerals may be oxidized or experience another impact that will lead to the creation of another substance.
The impact of physical weathering is barely noticeable on a short-term scale, yet becomes tremendous after taking place for a significant amount of time. Being affected by the forces described above, minerals disintegrate, causing physical decomposition of rocks. As a result, the landscape suffers massive changes. Among other effects of physical weathering, one must mention the creation of cracks known as joints in rocks and minerals.
For example, the Almo Pluton joints are famous for the grus in their landscape caused by rains and other forms of precipitation (National Park Service, 2018). The observed phenomenon affects granite alveoles in the Almo Pluton, thus creating a unique pattern in its landscape and making xenolith, particularly, quartz and feldspar turn into grus (National Park Service, 2018).
In addition, physical weathering has a profound impact on the structure of minerals. Apart from enforcing the physical breakdown of rocks into smaller parts, weathering alters the chemical structure thereof. Hydrolysis and oxidation as the most typical types of chemical weathering produce new substances. For example, when trickling into granite, water reacts with feldspar crystals (aluminosilicate minerals.), causing them to turn into clay, particularly, kaolinite (Clift, Wan, & Blusztajn, 2014).
Chemical weathering leads to dehydration, which drains a mineral of any presence of water (H2O) or hydroxide ions (HO). Another effect that chemical weathering may produce is the complete dissolution, which occurs once a mineral dissolves in water entirely (Israeli & Emmanuel, 2018). The specified phenomenon can be observed during carbonation, when precipitation reacts to the presence of carbon dioxide and releases carbonic acid, which makes rocks dissolve entirely. Carbonic acid breaks calcite into the calcium ion and bicarbonate ion, thus making the rock dissolve: “
” (Ahluwalia, 2017, p. 206). The changes occurring in the Inn River can be seen as the prime example of calcite dissolution (Schindlbacher et al., 2015).
The effects of organic weathering on the landscape and the environment include the scenarios in which organisms such as plants or animals make significant changes in the physical or chemical composition of minerals. For instance, the roots of a growing plant may place significant stress on a rock, eventually making it crack. The specified phenomenon can be observed quite often; for instance, a pipal tree can grow on rocks or even walls due to the intricate taproot system that penetrates the soil and, thus creates channels for water (Balasubramanian, 2014). As a result, rocks and minerals located in close proximity to pipal trees typically undergo weathering processes.
From an environmental perspective, the effects of weathering cannot be termed as either strictly negative or entirely positive. However, weathering is essential to making soil fertile by enriching it with minerals. However, a recent report indicates that the impact of weathering on environmental changes has been overrated (Balasubramanian, 2014). Particularly, the decomposition of rocks does not have a direct effect on the regulation of global temperature (Hickey, 2017). Consequently, weathering does not seem to contribute to global warming as one of the current environmental concerns to the same extent as it was assumed to be. Nevertheless, further analysis of weathering and its effects is required to embrace the geological change and predict possible outcomes.
References
Ahluwalia, V. K. (2017). Advanced environmental chemistry. New Delhi, India: The Energy and Resources Institute (TERI).
Balasubramanian, A. (2014). Geomorphic weathering. Mysore, India: University of Mysore.
Bland, W. J., & Rolls, D. (2016). Weathering: An introduction to the scientific principles. New York, NY: OUP.
Clift, P. D., Wan, S., & Blusztajn, J. (2014). Reconstructing chemical weathering, physical erosion and monsoon intensity since 25 Ma in the northern South China Sea: a review of competing proxies. Earth-Science Reviews, 130, 86-102. Web.
Eppes, M. C., & Keanini, R. (2017). Mechanical weathering and rock erosion by climate‐dependent subcritical cracking. Reviews of Geophysics, 55(2), 470-508. Web.
Hickey, H. (2017). Weathering of rocks a poor regulator of global temperatures. UW News. Web.
Israeli, Y., & Emmanuel, S. (2018). Impact of grain size and rock composition on simulated rock weathering. Earth Surface Dynamics, 6(2), 319-327. Web.
National Park Service. (2018). Geological features. Web.
Schindlbacher, A., Borken, W., Djukic, I., Brandstätter, C., Spötl, C., & Wanek, W. (2015). Contribution of carbonate weathering to the CO 2 efflux from temperate forest soils. Biogeochemistry, 124(1-3), 273-290. Web.