Difference between Denudation and Weathering

Difference Between Denudation and Weathering – UPSC Geography Notes

The Denudation process, which includes weathering and erosion, is a comprehensive term used to describe the various exogenic processes. ‘Denude’ signifies the action of exposing or removing something. These processes are impacted by the physical attributes such as folds, faults, orientation, bed inclination, the presence of joints, bedding planes, mineral hardness or softness, and permeability, as well as the chemical susceptibility of minerals to corrosion. This article provides an in-depth exploration of the denudation process, a crucial topic for UPSC exam readiness.

Concept of Denudational Processes

Denudational processes encompass the collective actions that lead to the degradation or removal of surface layers on the Earth. These processes play a vital role in shaping landscapes and are a subset of the broader category of exogenic or external geomorphic processes. Denudation comprises a series of consecutive processes:

  • Weathering: Initially, this involves the breakdown of rocks at or near the Earth’s surface due to various physical, chemical, and biological forces. Weathering does not entail the transportation of eroded materials.
  • Erosion: This process involves the displacement and transport of weathered material by various agents such as water, wind, ice, and gravity. Various forms of erosion contribute to the formation of diverse landforms and landscapes.
  • Transportation: It refers to the movement of eroded materials by agents such as rivers, winds, glaciers, and waves. Different agents employ distinct modes of transport, leading to the creation of various landforms.
  • Deposition: This is the process by which transported materials settle or get deposited in new locations. Over time, the accumulation of these deposited materials can give rise to landforms such as deltas, alluvial fans, beaches, and moraines.
Denudational Processes

Classification of Denudational Processes

Denudational processes can be classified into – Weathering, mass movements, erosional, and depositional processes. Let us look at these in detail:

Weathering

  • Weathering may occur through physical processes such as pressure release, abrasion, animal activity, plant growth, as well as chemical means involving water, carbon dioxide, living organisms, and the impact of acid rain, resulting in the disintegration of rocks over time.
  • As there is minimal or no movement of materials involved, weathering is considered an in-situ or on-site process.
  • The eroded weathered material is then transported to distant locations through the process of erosion. Weathering can be categorized into physical weathering, chemical weathering, and biological weathering.

Physical / Mechanical Weathering

  • Rock disintegration through mechanical means arises from temperature fluctuations, freeze-thaw cycles, wet-dry cycles, salt crystallization, as well as animal and plant activities, among other factors.
  • External factors significantly influence processes of physical or mechanical weathering. These include gravity forces such as overburden pressure, load, and shearing stress; expansion forces caused by temperature changes, crystal growth, or animal activity; and water pressure regulated by wetting and drying cycles.
  • The principal causes of physical degradation stem from thermal expansion and pressure.
Unloading and Expansion
  • Continual erosion leads to the release of vertical pressure as the overlying rock load is reduced. Consequently, the upper layers of the remaining rock expand, causing the disintegration of rock masses.
  • Exfoliation is not a deliberate process but an outcome. Smooth and rounded surfaces are generated by the peeling off of more or less curved sheets from rocks or bedrocks. Smooth circular exfoliation domes are formed due to unloading and expansion.
Temperature Changes and Expansion
  • Intrusive igneous rocks formed at great depths beneath the Earth’s surface experience significant pressure due to the underlying load.
  • When erosion removes the overlaying load, the vertical pressure is released, leading to the expansion and fracturing of higher rock layers parallel to the surface.
  • Exfoliation is the gradual detachment of rock sheets along cracks from exposed rocks over time. Sheeting is the specific term used for exfoliation induced by the release of pressure.
Freezing, Thawing, and Frost wedging
  • Frost weathering is a consequence of repeated cycles of freezing and thawing (as temperatures rise, leading to the melting of snow and ice).
  • This phenomenon is particularly prominent at high elevations in mid-latitudes where freezing and thawing occur frequently.
  • The sudden freezing of water induces rapid expansion and generates high pressure. Consequently, joints, cracks, and minor intergranular fractures widen due to this expansion, eventually leading to the breakdown of the rock.

Chemical Weathering

Chemical weathering involves the chemical decomposition of rocks and soil. It encompasses processes such as dissolution, solution, carbonation, hydration, oxidation, and reduction, which act on rocks, causing them to break down, dissolve, or reduce to a finer state. Acids produced by microbial and plant-root metabolism, water, air (including oxygen and carbon dioxide), and heat accelerate all these chemical reactions.

Chemical Weathering
Solution
  • A solution refers to the resulting water or acid when something dissolves in water or acids.
  • This process requires the solubility of a mineral in water or weak acids, leading to the elimination of solids in the solution.
  • Upon contact with water, many solids disintegrate and mix as a suspension in the water.
  • Minerals like calcium carbonate and magnesium bicarbonate in limestones dissolve in water containing carbonic acid (formed when carbon dioxide is introduced to water) and are transported away as a solution.
Carbonation
  • Carbonation refers to the reaction of carbonate and bicarbonate with minerals, commonly contributing to the disintegration of feldspar and carbonate minerals.
  • Water absorbs carbon dioxide from the atmosphere and soil air, leading to the formation of carbonic acid, which is a weak acid.
  • The dissolution of calcium and magnesium carbonates in carbonic acid results in cave formation, with the minerals being removed in solution without leaving any trace behind.
Hydration
  • Hydration is the chemical process of adding water to a substance, known as hydration. Minerals absorb water and undergo expansion, causing an increase in the volume of the substance or rock.
  • This process is reversible and occurs over an extended period, inducing strain in the rocks, which can eventually result in their disintegration. For instance, when calcium sulfate absorbs water, it transforms into gypsum, a less stable form of calcium sulfate.
Oxidation and Reduction
  • Oxidation in weathering denotes the mineral’s reaction with oxygen, resulting in the creation of oxides or hydroxides.
  • This process often involves minerals such as iron, manganese, and sulfur. As iron oxidizes, its red color transforms into brown and yellow hues.
  • The intrusion of oxygen leads to the disruption and breakdown of the rock. Conversely, when oxidized minerals encounter an oxygen-deficient environment, reduction occurs.

Biological Weathering​

Biological weathering results from a diverse array of biological activities including organism growth and movement, which can lead to both physical and chemical deterioration. Rock degradation and disintegration are facilitated by the actions of plants, animals, and bacteria in this process. Such weathering can occur due to physical stress, like the penetration of plant roots or the impact of animal hooves, as well as chemical transformations instigated by entities such as worms and lichens.

Biological Weathering​

Mass Movements

These processes facilitate the downward transport of rock debris mass under the influence of gravity. Weathered slopes exhibit greater activity in mass movements compared to unweathered slopes. Common geographical agents such as running water, glaciers, wind, and waves have minimal involvement in mass motions, with gravity serving as the predominant driving force. Mass movements can be classified into two categories: slow and fast movements.

Slow Movements

Soil Creeping
  • This phenomenon takes place on moderately steep slopes covered with soil and doesn’t rely on water lubrication, unlike solifluction.
  • The movement is incredibly slow and often imperceptible, requiring prolonged observation to notice any significant changes.
  • You might have observed that electric poles in hilly areas have gradually deviated from their original horizontal positions. This phenomenon is known as “creep effect.”
Soil Creeping
Solifluction
  • This refers to the gradual downward movement of water-saturated or lubricated soil mass or fine-grained rock debris.
  • It represents a type of creep where the movement is influenced by the presence of lubricating water.
  • It predominantly occurs in permafrost zones where the groundwater strata are located between permanently frozen soil and rocks.
Solifluction

Rapid Movements

Earthflow

Earthflow signifies the downward movement of water-saturated clayey or silty earth materials along low-angle terraces or hillsides.

Mudflow

Mudflows are formed when substantial layers of weathered materials become saturated with water and flow along specific pathways, particularly in the absence of vegetation and ground cover, triggered by heavy rainfall.

Debris Avalanche

This phenomenon is more common in both vegetated and non-vegetated humid regions. Resembling a snow avalanche, it occurs within narrow passages on steep mountains.

Rapid Movements
Landslides

Contrary to the swift mass movements mentioned earlier, the materials involved in landslides are typically dry. Landslides can take several forms, including slumps, debris slides, and rockslides:

  • Slump: In this type of landslide, numerous units of rock debris slide backward concerning the slope during the movement.
  • Debris slide: Unlike the slump, there is no backward rotation in this form of landslide. The descent is nearly vertical.
  • Rockslide: This term describes the movement of individual rock masses.

Erosion (Transportation) and Deposition

  • Erosion involves the gathering and transportation of rock debris by various geomorphic processes, including running water, wind, and waves.
  • While weathering can intensify erosion, it is not a prerequisite for erosion to take place (meaning erosion can occur in both weathered and unweathered environments).
  • Deposition, on the other hand, is a consequence of erosion.
  • On moderate slopes, the velocity and energy of erosional agents decrease, leading to the settling of the materials they carry.
  • Unlike erosion, no external agents are involved in the deposition process; it is a result of the erosional effects.
Erosion (Transportation) and Deposition

Conclusion

Denudational processes encompass weathering, mass wasting, erosion, and deposition. The term ‘denudation’ encompasses all exogenic processes, signifying the removal or uncovering of material. Natural elements such as wind, water, and waves act as geomorphic agents, executing these exogenic processes. Gravity and gradients serve as the two factors that render these agents mobile.

FAQs

Q: Weathering क्या होता है?

A: Weathering एक प्रक्रिया है जिसमें पत्थर, चट्टान और पथरीले पदार्थ धीरे-धीरे टूट जाते हैं या पिघल जाते हैं ताकि वे आसानी से हट सकें।

Q: Weathering शब्द का हिंदी अर्थ क्या है?

A: Weathering का हिंदी में अर्थ ‘मौसमीकी’ होता है, जो पत्थर, चट्टान या अन्य सतही पदार्थों के टूटने या पिघलने की प्रक्रिया को संदर्भित करता है।

Q: How is weathering different from erosion?

A: Weathering refers to the breakdown of rocks or minerals on the Earth’s surface, whereas erosion involves the process of removing and transporting the weathered materials by agents such as wind, water, or ice.

Q: What are weathering and erosion?

A: Weathering is the process of breaking down rocks and minerals on the Earth’s surface, while erosion is the process of removing and transporting the weathered materials to other locations.

Q: How many types of weathering are there?

A: Weathering is typically categorized into two main types: mechanical weathering and chemical weathering.

Q: Are weathering and erosion the same thing?

A: No, weathering and erosion are distinct processes. Weathering refers to the breakdown of rocks, whereas erosion involves the transportation of the weathered materials from one place to another.

Q: How are weathering and erosion related?

A: Weathering and erosion are interconnected natural processes. Weathering breaks down rocks into smaller particles, which are then transported and deposited by erosion.

Q: தமிழில் வெளிப்படுத்தல் என்றால் என்ன?

A: வெளிப்படுத்தல் என்பது மலை அல்லது புறம் நிலத்தில் உள்ள கற்களின் நிறம், உறவுகள் மற்றும் அகமத்தை அழிக்கும் சமீபத்தில் நீரில் மற்றும் காற்றில் இருப்பதாக விளக்கம் செய்யப்படுகின்றது.

Q: বাংলায় মাটির অপসারণ কি?

A: মাটির অপসারণ বা মাটির উপরে বিভিন্ন পরিস্থিতিতে ঘাস, পাতা, প্রাকৃতিক উপাদানগুলির ও ভেঙ্গে পড়ে যাওয়ার প্রক্রিয়াটিকে বুঝায়।

Q: বাংলায় “অর্পণ” শব্দের অর্থ কী?

A: “অর্পণ” বাংলায় অর্থ করে অনুদান বা শ্রদ্ধা।

Q: मराठीत “अपघात” अर्थ काय आहे?

A: अपघात होते माल, पहाड किंवा जमीनच्या कोणत्याही अंशावरील चट्टाणांची रंग, संरचना आणि अग्नी असे परिणाम प्राप्त होणारी प्रक्रिया.

Q: മലയാളത്തിൽ പട്ടം എന്നാൽ എന്താണ്?

A: പട്ടം എന്നത് മലനിരക്കുകളും ഭൂമിയും നിന്നും ചരിത്രപൂർവ സമയങ്ങളിലും പൂർവനിരക്കുകളും അപസരിക്കപ്പെട്ട ശൈലിയാണ്.

Q: What is the meaning of denudation of soil?

A: Denudation of soil refers to the process of stripping or removal of the top layer of soil due to natural agents such as wind, water, or ice.

Q: What is denudation in geography?

A: In geography, denudation refers to the overall process of wearing away the Earth’s surface through the combined actions of weathering and erosion.

Q: What is denudation in class 10?

A: In the context of class 10 geography, denudation is the process of erosion that involves the removal of the Earth’s surface materials through various natural agents.

Q: What is the denudation process?

A: The denudation process involves the gradual wearing away and removal of the Earth’s surface materials through weathering, erosion, and other natural processes.

Q: What is denudation in class 7?

A: In the context of class 7 geography, denudation refers to the process of the gradual removal of surface materials from the Earth’s crust by natural forces such as wind, water, and ice.

Q: What does denudation mean?

A: Denudation refers to the process of erosion or the stripping away of the Earth’s surface materials, including rocks, soil, and other geological elements, by various natural agents such as wind, water, and ice.

For Daily Current Affairs Click Here

Join our Official Telegram Channel HERE
Subscribe to our YouTube Channel HERE
Follow our Instagram ID HERE

Similar Posts

Leave a Reply

Your email address will not be published. Required fields are marked *