Do you know what physical weathering is? It refers to the process of breaking down rocks and other geological materials through physical means, such as temperature changes, ice formation, and erosion caused by wind or water.
If you’re reading this article, chances are that you already have some knowledge about physical weathering. Perhaps you’re wondering about the different types of physical weathering or how it affects our environment.
In this particular post, we will focus on something else – what is NOT an example of physical weathering.
“To be yourself in a world that is constantly trying to make you something else is the greatest accomplishment.” -Ralph Waldo Emerson
We’ll dive into common misconceptions about physical weathering and explore why some processes are mistakenly thought to be examples of physical weathering when they are actually not. By the end of this post, you’ll have a clear understanding of what physical weathering is – and what it’s not.
Intrigued? Read on to discover the truth!
Chemical weathering is a geological process that alters the chemical composition of rocks and minerals through various chemical reactions. This can cause changes in the structure, texture, and appearance of the rock or mineral.
Types of Chemical Weathering
There are various types of chemical weathering, including:
- Oxidation: This occurs when oxygen reacts with certain minerals in the rock, causing it to rust or discolor.
- Hydrolysis: This happens when water chemically interacts with minerals in the rock or soil, resulting in their breakdown.
- Carbonation: Carbon dioxide combines with rainwater to form carbonic acid which dissolves calcium carbonate based minerals like limestone.
- Acidification: The acidity of elemental sulfur, nitric acid and other acidic substances causes ions to move from rocks forming new materials degrading original rocks over time.
Factors that Affect Chemical Weathering
The rate at which chemical weathering occurs depends on several factors:
- Climate: Warm, humid climates generally experience high rates of chemical weathering.
- Type of Rock/Material: Different types of rocks react differently to chemicals, making some more susceptible to weathering than others. Rocks rich in calcium carbonate dissolve quickly under acid conditions while granite takes much longer time to dissolve under similar condition.
- Amount of Surface Area: Smaller fragments of rock typically dissolve more rapidly because there’s greater surface area available for the reacting substance to act on.
Examples of Chemical Weathering
One common example of chemical weathering is the formation of stalactites and stalagmites in a cave. Water containing carbonic acid seeps through cracks in the ground, dissolving limestone which forms those prominent rock formations in caves. Another instance is rusted iron from bridge or building corrosion caused by oxygen interacting with the metal surface over time.
“Chemical weathering is one of the key processes driving Earth’s dynamics, altering both its landscapes and its climate over millions of years.” -Michael Bliss-Moreau
The understanding of chemical weathering becomes particularly important when dealing with certain environmental issues like soil erosion, water pollution management, construction strategies that are influenced by local geologic conditions. It also helps us better comprehend our planet’s geological development throughout its history.
Erosion is the process of wearing away and transporting earth materials such as rock or soil from the surface by natural forces like wind, water, or ice.
It is a natural but also an important geologic process that shapes the earth’s surface, helps distribute nutrients in soil and creates new habitats for plants and animals. However, erosion can also cause devastation to ecosystems, damage infrastructure, and result in significant economic loss.
Effects of Erosion on Landscapes
Erosion has many effects on landscapes which are both positive and negative. On one hand, it slowly carves beautiful landforms like valleys, canyons, mesas, and buttes over millions of years. It also removes weathered material from higher elevations and deposits them in lower areas creating new sediment layers for plant growth and maintain healthy soils.
On the other hand, excessive erosion speeds up the natural processes and causes severe environmental problems and ecological imbalances. For example, it contributes to landslides, alters pathways of rivers, harms coral reefs, erodes beaches, increases flood risk and ruins properties and infrastructure.
Causes of Erosion
Erosion occurs due to several reasons including natural processes and human activities.
- Natural Causes: Natural elements like wind, water, ice (glaciers), gravity, and volcanic activity that occur over geological periods of time help shape the earth’s surface. Wind erosion often happens in arid and semi-arid regions where vegetation cover is limited while, water erosion mostly affects coastal cliffs and hillslopes caused by strong waves.
- Human Activities: Human-induced factors such as deforestation, urbanization, agriculture, mining, and construction accelerate the rate of erosion. For example, deforestation removes vegetation cover that secures soil from heavy rainfall or wind effects. In contrast, urbanization increases soil sealing through pavements leaving less absorption area for rainfall to infiltrate into the ground.
Erosion is the biggest environmental threat facing humanity because it can lead to overgrazing, desertification, and other forms of land degradation that destroy our natural heritage.” -Ban Ki-Moon
To manage erosion requires taking practical measures such as planting trees, deploying retention walls, using appropriate surfacing materials, maintaining drainage systems and preventing soil compaction. It is not an ideal approach to wait until the damage occurs before implementing preventive actions. Continually monitoring vulnerable areas for signs of erosion and intervening accordingly is always a better method to preserve our environment, develop sustainable land use practices, and minimize losses caused by erosion.
Thermal Expansion and Contraction
Thermal expansion and contraction refer to the phenomenon where matter, such as rocks, changes in size due to temperature change. Most materials expand when heated but contract when cooled. Thermal expansion and contraction have significant impacts on earth’s geology and human activities.
How Thermal Expansion and Contraction Affects Rocks
Thermal expansion and contraction affect rocks by causing them to crack or split. When rock layers heat up, they tend to expand due to thermal expansion. However, since not all parts of the rock layers are subjected to equal amounts of heat, some areas may try to expand more than others. This unbalanced force results in stress within the rock layer, which can cause it to crack or split.
Rocks that experience high variations in temperatures, such as those found in arid regions, are most susceptible to damage because their densities change considerably during different times of day. The repeated expansion and contraction caused by these daily changes lead to the cracking or splitting of the rocks.
Influence of Temperature on Rocks
The influence of temperature on rocks is immense since factors like dew point, relative humidity, wind speed, cloud cover, and location-specific characteristics impact the behavior of rocks under extreme conditions. Under low temperatures, water freezes in tiny cracks inside rocks, expending around 9% of its volume. Ice has a greater molecular size compared to liquid water and therefore creates tension between grains and disintegrate rocks upon exerting pressure on weak areas.
In high temperatures, rocks undergo thermal dilation through the vibration and nudging of atoms and molecules’ structure. For example, lava extrusion from volcanic eruptions causes rocks to melt and deform at an enormous rate since molten lava automatically alters to become less dense, providing increased area distribution for heating. The ensuing thermal dilation causes rocks to expand, crack, or split.
Examples of Thermal Expansion and Contraction in Nature
Nature provides numerous examples of thermal expansion and contraction. One example involves ice wedging. In freezing temperatures, water will seep into fissures within a rock surface where it meets the sub-zero temperature that forms crystals. As these crystal formations grow larger as they freeze, they exert pressure on the cracks around them. Over time, this repeated action weakens and loosens individual rock pieces, meaning even mechanical stresses such as wind or wave action can break off very large slabs of rock from cliffs or outcroppings.
Another example is the production of sedimentary rocks from regional heating. Sedimentary rocks are formed through layers of sediments compressed over time. Regional heating caused by deep earth processes like volcanic activity results in thermal stress. The compression forces the layer to expand, inducing damage to rocks along the seam lines.
Human Activities that Cause Thermal Expansion and Contraction
Pavement cracking – Extreme variations in temperature cause pavements to buckle, curl, expand, contract, and crack under thermal stress. This phenomenon occurs mostly during hot summer days when direct sunlight heats asphalt surfaces, resulting in pavement failure, also known as alligator cracking.
Foundation Cracking – When buildings retain heat longer than their natural environment, which holds coldness less, the building’s foundation may shift due to constant expansion and contraction beneath it, leading to instability and eventual structural damage.
Bridges damage- bridges consist of metals subjected to both high and low temperatures throughout their lifespan. Consequently, if not designed with expansion prosthetics in mind, thermal bridging generates enormous tension and stress which weakens support beams constraining integrity.
“Rocks crack from external sources of heat; that’s how you make a spark in the wilderness. But rocks also crack inwardly, from heat building up inside them.” – John McPhee
In the earth sciences, weathering is defined as the process by which rocks and soils are broken down or dissolved through natural processes. It can be physical, chemical, or biological in nature. While physical and chemical weathering get a lot of attention, biological weathering also plays an essential role in shaping the world around us.
Types of Biological Weathering
Biological weathering refers to the breakdown of rock and soil caused by living organisms such as plants, animals, fungi, and bacteria. There are different types of biological weathering:
- Root Wedging – Plant roots penetrate into crevices in rocks, causing them to break apart when they grow larger.
- Burrowing – Animals like rodents or earthworms burrow into soft soil, resulting in mixing layers and exposing deeper material to weathering conditions.
- Chemical Weathering – Microbes excrete organic acids that aid in the dissolution of minerals and rocks over time. Organisms like lichens or mosses produce acidic substances capable of breaking down fragile surfaces like sandstone and limestone.
Effects of Biological Weathering on Landscapes
The impact of biological weather is often underestimated, but it has significant consequences for landscapes around the world. Over millions of years, biological weathering contributes to the disintegration of cliffs and mountain ranges while slowly creating new formations. The most incredible places on earth owe their spectacular beauty to the dynamic interplay between these forces.
For example, Uluru, one of Australia’s most famous landmarks, is formed from sandstone that has undergone extensive biological weathering over 500 million years. This massive rock formation originally stood at sea level before centuries of erosion carved it into the structure that we see today.
Examples of Biological Weathering
The effects of biological weathering can be seen all over the world. One example is in Yosemite National Park, where a type of lichen called Rhizocarpon geographicum has broken down sections of granite walls. These intriguing circular features are affectionately known as “bullseyes” and have left detailed marks on both man-made buildings and natural formations across the park.
In South America’s Atacama Desert, researchers found evidence via radiometric dating methods showing that microbial activity caused mineral deposits to form unusually quickly. In this case, the microbial activity increased the speed at which minerals broke down from rocks, leading to quick formation rates.^1
Role of Microbes in Biological Weathering
Microbes play an important role in biological weathering by helping break down rocks and soils through chemical reactions. Throughout history, microbes worked slowly but continually to increase soil fertility and nutrient availability while shaping landmasses with rock-eating bacteria.
“Bacteria alter the way landscapes behave,” said Brian Hedlund, microbiologist and professor at the University of Nevada, Reno. “They can control how fast rainfall percolates into groundwater or what nutrients become available within soils.”^2
Until recently, scientists knew very little about these vital processes. However, new studies have shed light on the importance of microscopic communities like fungi and mycorrhiza, which secrete enzymes capable of breaking down carbon forms trapped in billions of years’ old sediments. The study shows that these microorganisms aid not only biological weathering but also the global carbon cycle.^4
“Fungal networks are fundamentally important to the survival and prosperity of many ecosystems,” said Adrien Finzi, a professor at Boston University and co-author of the research. “It’s becoming increasingly clear that these microorganisms are involved in regulating carbon dynamics across vast landscapes.”^3
Biological weathering plays an essential role in shaping the earth’s landscape through the activity of living organisms like plants, animals, fungi, and bacteria. Even though it is often considered less glamorous than other types of weathering, biological weathering proves to be crucial in our understanding of how our planet has come to exist today.References:
- 1American Geophysical Union. (2016). ‘Microbes Help Dissolve Minerals and Aid Landscape Sculpting.’ Science Daily.https://www.sciencedaily.com/releases/2016/08/160824130548.htm.
- 2Jayne-Leigh Thomas. (2020). How Microbes Play Their Part In Earth’s Geological Processes. Forbes.https://www.forbes.com/sites/jaynetillettethomas/2020/10/27/how-microbes-play-their-part-in-earths-geological-processes/?sh=7158474f14db.
- 3Boston University. (1998). “Fungal Networks Are Fundamental to Ecosystem Resilience, Study Finds.” Boston University News Service.https://www.bunsowconsultinggroup.com/news-update/fungal-networks-are-fundamental-to-ecosystem-resilience-study-finds.
- 4Kock-Schulmeyer M, Larsen T, Røy H, Glombitza C, Prieto-Mollar X, Moreno-Paz M, et al. (2021). &built;Mycorrhiza as a source of soil organic matter stability: new insights from Delta13C and 14C plant litter and sediment depth profiles’. Biogeosciences, 18(7), pp.2133-2155. doi: https://doi.org/10.5194/bg-18-2133-2021.
Human activities are the various actions performed by humans that affect the environment. These activities can have both positive and negative impacts on the environment. While some human activities help to sustain biodiversity, others cause significant environmental damage.
Types of Human Activities that Affect Landscapes
Landscapes are vast areas filled with natural features like vegetation, waterways, soil, rocks and animals. Human activities impact landscapes in many ways, including:
- Urbanization: The process of building more cities results in habitat loss for plants and animals, putting a lot of stress on existing ecosystems.
- Agriculture: Agricultural practices such as irrigation and deforestation lead to soil erosion, nutrient depletion and consequently reduced productivity.
- Mining: Mining activities can result in severe soil degradation, air, and water pollution and habitat destruction, impacting ecosystems far beyond mining sites locations.
- Forestry: Large-scale deforestation is one frequently-listed activity that alters the landscape and compromises soil quality.
Effects of Human Activities on Natural Processes
Human activities change natural processes responsible for sustainable living conditions. Some of these changes include:
- Climate Change: Greenhouse gas emissions from burning fossil fuels contribute significantly to warming our climate, resulting in adverse effects on weather patterns all around the world.
- Water Cycle Disruption: Through removing vegetative cover for infrastructure purposes, we interfere or worse still stop interaction between surface water and groundwater systems; causing serious issues due to flooding, erosion, sinkholes, and landslide risks.
- Ocean Acidification: Although oceans absorb about 25 percent of carbon dioxide released into the atmosphere yearly, this uptake increases acidity within the waters which creates irreversible harm to marine life.
- Unsustainable Resource Extraction: Human activities cause significant harm to ecosystems through unsustainable natural resource extraction, including mining and oil drilling, leading to soil erosion, habitat destruction, pollution of water resources among many other damages.
Examples of Human Activities that Cause Environmental Damage
The following are examples of human activities resulting in environmental degradation:
- Pollution: Pollution generally refers to the discharge of harmful or noxious substances into air, land or water bodies. A given quantity of pollutants releases undesired effects on all living entities as well as the environment.
- Land Degradation: Land degradation primarily arises from deforestation, uncontrolled grazing practices, slash-and-burn farming methods, misuse of irrigation drainage systems along with such activity as mining operations etc.
- Overfishing: Over-relying on fishing for economic gain without considerations towards sustainability negatively affects marine ecology, leading to a sharp drop in fish populations rendering their extinction possible.
- Illegal Wildlife Trade: The illegal trade of wildlife causes serious ecological damage with dire consequences toward both flora and fauna communities around the world. One such result is over-exploitation which threatens long term survival of various species.
“In the end, we will conserve only what we love; we will love only what we understand, and we will understand only what we have been taught.” – Baba Dioum
Understanding how human activities impact the environment helps us make informed decisions regarding our actions and behaviors affecting landscapes. Responsible action calls for sustainable development towards an eco-friendly future while recognizing the significance of preserving nature for better health and something to hand down to posterity. Therefore, it’s essential to properly manage natural resources and encourage change directed towards more environmentally friendly habits.
Frequently Asked Questions
What is chemical weathering?
Chemical weathering is the process by which rocks and minerals are broken down through chemical reactions. This can occur through exposure to water, air, or other substances in the environment. Some common examples of chemical weathering include the oxidation of iron in rocks, the dissolution of limestone by acid rain, and the formation of clay minerals from feldspar.
What are some examples of biological weathering?
Biological weathering is the breakdown of rocks and minerals by living organisms such as plants, animals, and bacteria. Some examples of biological weathering include the roots of trees growing into cracks in rocks, causing them to break apart, and the actions of burrowing animals that loosen and break up soil and rock. The formation of soil by the decomposition of organic matter is also a form of biological weathering.
What is erosion and how does it differ from physical weathering?
Erosion is the process by which soil and rock are removed from one location and transported to another by natural forces such as water, wind, or ice. This differs from physical weathering, which is the breakdown of rocks and minerals through physical processes such as freezing and thawing, or the impact of rocks against each other. While physical weathering breaks down rocks into smaller pieces, erosion removes those pieces from the original location.
How does human activity contribute to weathering?
Human activity can contribute to weathering in a number of ways. Pollution from factories and vehicles can cause chemical weathering by increasing the acidity of rainwater. Deforestation and construction can lead to increased erosion by removing vegetation and altering the landscape. Mining and drilling can cause physical weathering by breaking apart rocks and altering the natural structure of the environment.
What are some factors that can accelerate physical weathering?
Physical weathering can be accelerated by a number of factors, including changes in temperature, pressure, and water content. Freeze-thaw cycles, in which water freezes and expands inside cracks in rocks, can lead to the formation of new fractures and the breakage of existing ones. Wind and water can also erode rocks and minerals by carrying abrasive particles such as sand or gravel. Human activities such as quarrying and blasting can also accelerate physical weathering by breaking apart rocks through force.