Fundamentals of Physical Geography

Chapter 6: Geomorphic Processes

Q. 1 Give the difference between Endogenic and Exogenic forces.
 Answer Key Points: -
1. Definition
  • Endogenic forces are the forces which are active within the Earth due to the internal radioactivity.
  • Exogenic forces are the forces which are active on the surface of the Earth due to gravitational forces.
2. Nature
  • They are known as land building forces because they create new features or landforms on the surface of the Earth.
  • They are known as land wearing forces because they degrade and perform the physical features of the Earth.
Exogenic Forces
3. Results
  • Upliftment and ground substance are the results of endogenic forces.
  • Weathering, mass wasting, Earth movements, erosion and deposition are the results of exogenic forces.
4. Speed
  • Endogenic forces can result in both slow and/ or sudden motions.
  • Exogenic forces will always lead to slow motions.
5. Examples
  • Earthquakes and volcanoes etc. are major endogenic forces.
  • Temperature, actions of wind, water and glaciers etc. are the major exogenic forces.
Q. 2 What is ‘Diastrophism’? What factors have caused diastrophism?
 Answer Key Points: -
Diastrophism, also called tectonism, includes all the processes that move, elevate or build up portions of the Earth’s crust by natural processes, which leads to the formation of continents and ocean basins, mountain systems, plateaus, rift valleys, and other. Diastrophism is the general term applied to slow bending, folding, warping, and fracturing.
 Diastrophism include: -
1) Orogenic Processes: - This process includes mountain building by folding and faulting. They affect long narrow belts of the Earth’s crust through horizontal movement.
2) Epeirogenic Processes: - Epeirogeny is a continental building process. This process involves uplift or warping of large parts of the Earth’s crust through vertical movement.
3) Earthquakes: - An Earthquake is the shaking of the surface of the Earth resulting from a sudden release of energy in the Earth's lithosphere that creates seismic waves.
4) Plate Tectonics: - It involves horizontal movements of crustal plates. All these processes-cause pressure, volume and temperature (PVT) changes which in turn induce metamorphism of rocks.
Q. 3 What is the sole driving force behind all the exogenic processes? Explain how? Or
Exogenic geomorphic processes derive their ultimate energy from the sun’s heat. Explain.
 Answer Key Points: -
  • 1) Solar energy is the sole (main) driving force behind all exogenic processes. Exogenic processes derive their energy from atmosphere determined by the ultimate energy from the sun and also the gradients created by tectonic factors.
  • 2) Various minerals in rocks possess their own limits of expansion and contraction. With rise in temperature, every mineral expands and pushes against its neighbor and as temperature falls, a corresponding contraction takes place.
  • 3) Sunlight causes air to move, water to evaporate, and ocean waves to rise. These moving fluids like water, wind and waves, etc. attack the solid surface, eroding it, carrying the broken pieces far away, and depositing them to fill low places in the landscape.
  • 4) In the process of weathering, the rocks are disintegrated by physical forces and decomposed by chemical action. Agents of physical weathering such as insolation, frost, etc., wholly depend upon energy derived from the sun.
  • 5) The agents of denudation like river, glacier, wind, sea waves, etc., also derive their energy from the sun.
Q. 4 Define the term Denudation. Explain the process of Denudation.
 Answer Key Points: -
The word ‘Denude’ means to ‘Strip off’ or ‘To Uncover’ It is a group of processes by which Earth’s material is broken down, transported and deposited to new areas.
1) Mass Wasting/Movements: - Mass wasting also known as slope movement or mass movement, is the geomorphic process in which bed rock, rock debris, or soil, sand, regolith, and rock moves downslope in bulk, or as a mass, because of the pull of gravity.
2) Weathering: - Weathering is defined as process of physically disintegration and chemically decomposition of rocks. Pressure, volume, temperature (PVT) and biological activities are responsible for weathering.
3) Erosion: - The removal of surface material from Earth's crust, such as soil & rock debris, and the transportation of the eroded materials by natural agencies like water, wind and glaciers.
4) Transportation: - In Geology, transfer of eroded or weathered material (Rock Debris) from one place to another by agents of running water and wind, ice or gravity etc. is called transportation.
Q. 5 What are the difference between physical weathering and chemical weathering? 
Or
Are physical and chemical weathering processes independent of each other? If not, why? Explain with examples.
 Answer Key Points: -
No, physical and chemical weathering are not independent of each other. They are different but still interdependent.
1. Definition
  • The disintegration of rocks by physical or mechanical process is called physical weathering.
  • Chemical weathering is defined as the chemically decomposition of rocks by due to reaction of chemicals available in the rock under the influence of weather and climate.
2. Nature
  • In physical weathering there is no chemical change in the rocks and they break down due to physical processes.
  • There is not much importance of physical forces but rocks broken down due to chemical changes.
3. Results
  • Physical weathering is more effective in dry and cold areas.
  • Chemical weathering is more effective in hot and humid areas.
4. Speed
  • Rocks affected up to a great depth, strong minerals in the rocks are also affected by physical weathering.
  • Rocks are not affected to greet death chemically resistant minerals such as quartz are not much affected by chemical weathering.
5. Examples
  • The agents of physical weathering are temperature, frost and pressure release.
  • The agents of chemical weathering are oxidation, carbonation, hydration and solution.
Q. 6 How does biological weathering take place?
 Answer Key Points: -
Disintegration of rocks due to biological processes is called Biological weathering. These processes include actions of animals, vegetation and bacteria (Micro-organisms) and human activities.
1) Role of Animals: - Animals like rabbits, rats, termites, etc. make burrows and holes in the rocks. They consume large quantity of soils and rocks for making their habitat and destruction of food. This reduces the rock strata and disintegration.
2) Role of Vegetation: - Long and tenacious roots of plants work down into cracks of rocks. The roots of shrubs and trees reach deep into them and this leads to large blocks.

3) Role of Microorganisms: - Microorganisms in the soil and on the surface of rock can contribute. Some bacteria derive nutrition by taking a combination of nitrogen from the air and minerals from rock. By removing these minerals, the rock is weakened and is further subject to other weathering forces such as wind and water.
4) Human Activities: - Mining, deforestation, indiscriminate cultivation of land and construction activities contribute to weathering.
Q. 7 It is weathering that is responsible for bio-diversity on the Earth. How? Or
What is the importance of weathering? 
 Answer Key Points: -
  • 1) Weathering processes are responsible for breaking down the rocks into smaller fragments and preparing the way for formation of not only regolith and soils but also erosion and mass movement.
  • 2) Biomes and bio-diversity is basically a result of forests depend upon the depth of weathering.
  • 3) Weathering is an important process in the formation of soils.
  • 4) Weathering helps in the enrichment and concentrations of certain valuables ores of iron, manganese, aluminium, etc. which are of great importance for the national economy.
Q. 8 What factors activate the process of mass movement?
 Answer Key Points: -
  • 1) Removal of support from below to materials above through natural or artificial means.
  • 2) Increase in gradient and height of slopes.
  • 3) Overloading through addition of materials naturally or by artificial filling.
  • 4) Overloading due to heavy rainfall, saturation and lubrication of slope materials.
  • 5) Removal of material or load from over the original slope surfaces.
  • 6) Occurrence of Earthquakes, explosions or machinery.
  • 7) Excessive natural seepage.
  • 8) Heavy drawdown of water from lakes, reservoirs and rivers leading to slow outflow of water from under the slopes or river banks.
  • 9) Indiscriminate removal of natural vegetation.
Q. 9 Define the term landslide. Give different types of landslides.
 Answer Key Points: -
A landslide is defined as the movement of a mass of rock, debris, or Earth down a slope. Landslides are a type of "mass wasting," which denotes any down-slope movement of soil and rock under the direct influence of gravity.
 The types of Landslides: -
1) Slumps: - The slipping of one or several units of rock debris with a backward rotation with respect to the slope over which the movement takes place. Slumps generally form due to removal of a slope base, either from natural or manmade processes.
2) Debris Slide: - Rapid rolling or sliding of Earth debris without backward rotation of mass is known as Debris slide. Debris avalanches differ from debris slides because their movement is much more rapid than debris slides.
3) Rockslide: - When big rock rolls down the slope along the bedding plane and settle down at the base of the mountain slope this is called Rock slide.
4) Rock fall: - Rock fall is free falling of rock blocks over any steep slope keeping itself away from the slope. Rock falls occurs from the superficial layers of the rock face. It is the most rapid type of mass movement.
Q. 10 Without gravity and gradient will there be no erosion. Analyse the Statement.
 Answer Key Points: -
  • 1) Gravity activates down slope movement of matters and also causes stresses on Earth material.
  • 2) Without gravity and gradients there would be no movement, no erosion, no transportation and no deposits as gravitation stresses are as important as the other geomorphic process.
  • 3) Gravity is force that keeps us in contact with the surface and also switches on the movement of all surface material on Earth.
  • 4) All the movement either within the Earth or on the surface of the Earth occurs due to gradients from higher levels to lower levels and from high pressure to low pressure areas.
Q. 11 Give the difference between erosion and deposition.
Or
Deposition is the result of erosion. Explain.
 Answer Key Points: -
1. Definition
  • Erosion is a process of geological denudation, which involves the breakdown and transport of rock materials.
  • The process by which sediment settles on a particular location that are transported by water or wind.
2. Nature
  • Erosion is seen as a sequence of events it is the beginning of a process.
  • Deposition takes place at last when the rock particles finally settle down on the surface of Earth. So, deposition is the end of the same long process.
3. Results
  • It results to breaking down of landforms on surface of the Earth
  • It results to filling of Earth’s depression.
4. Origin
  • Erosion can happen because of degradational activities of natural agents such as water, ice, and wind.
  • Deposition takes place due to agradational activities of natural agents as they cannot keep on dragging the particles.
Q. 12 Define the term ‘Erosion’. Explain about different types of erosion by water.
 Answer Key Points: -
Soil Erosion is one form of soil degradation. It occurs in almost all types of lands. Flowing water, rainwater, and the wind are the prime agents which cause a significant amount of soil loss each year. Soil erosion on large scale causes serious loss of topsoil and also reduces crop production capacity, degrade surface water quality, and damaged drainage networks.
 Types of Soil Erosion By Water: -
1) Rain Drop or Splash Erosion: - It is the first stage in the erosion process in which structure of the soil surface is destroyed and removed by falling of raindrops. It is the primary cause of soil detachment and soil disintegration.
2) Sheet Erosion: - This is the second stage of erosion, Sometimes the top layer of soil over large areas is washed away as a sheet by water flows. This is known as sheet erosion or sheet wash. Sheet erosion occurs when rainfall intensity is greater than infiltration (sometimes due to crusting).
It is mainly done by the action of raindrop splash, shallow flows of surface of water, or even by wind.
3) Rill Erosion: - Rill erosion is a form of water erosion in which small finger like features (less than three inches) or not so straight numerous narrow channels called rills, streamlets, or head cuts are formed due to running water. Rill is the most common form of erosion, which you can also observe during heavy rain.
4) Gully Erosion: - It is the next stage of rill erosion. When the erosion continues and rills become deeper and wider due to headward erosion or even by slumping of side walls, which convert them into channels. This is called gully erosion. Gully erosion occurs due to the runoff of surface water causing the removal of soil with drainage lines.
5) Stream Bank Erosion: - Bank erosion is nothing but wearing away of the banks of a stream or a river. It is different from the erosion of the bed of a water course that is referred to as scouring. This type of erosion is also termed as Stream Bank Erosion. In this erosion the roots of trees growing by a stream bind the soil tightly and they form abutments which come out over the water.
6) Tunnel Erosion: - It occurs when excess surface water moves into and through dispersive (usually sodic) sub-soils. Dispersive soils are poorly structured so they erode easily when wet. The tunnel starts when surface water moves into the soil along cracks or channels or through rabbit burrows and old tree root cavities.
Q. 13 Give the reasons for soil erosion.
Or
Explain the causes of soil erosion.
 Answer Key Points: -
Running water is one of the main causes of soil erosion. Some soil erosion causes are mentioned below.
1) Due to Soil Texture: - If the texture is loose it helps the geomorphic agents to increase the rate of soil erosion as small particles can be easily lifted and transported by wind and water.
2) Slope: - Slope of land also determines the rate of soil erosion. Higher the gradient higher the rate of erosion.
3) Intensity or Amount of Rainfall: - Amount of rainfall also determines soil erosion. More intense rain, more erosion. The soil erosion can be a bit slow if there is more vegetation present in the land as the roots of the plants hold soil.
4) Human Activities: - Human activities play an important role in the process of soil erosion. Agricultural practices, deforestation, construction of roads, urbanization and global warming are a few major causes of soil erosion.
5) Deforestation: - Mismanaged utilization of soil resources like the removal of forest cover causes soil erosion heavily. Due to increasing land demand, the human is more into deforesting lands. Tree roots act as a binder of the top layer of the soil.
Q. 14 Why are parent material and time considered as passive control factors in soil formation? 
Or
What are the factors responsible for the formation of Soil?
 Answer Key Points: -
1) Parent Material: - Parent material in the form of rock and sediment builds the initial substance for soil formation. It defines a soil’s chemical and mineralogical composition and influences soil texture and structure. The kind of parent material also influences the rate at which soil forming processes take place.
2) Relief: - Relief and topography define the micro-climatic conditions under which soil formation takes place, as well as the closeness of soil to the ground water table. Soils that developed on higher elevations and sloping areas are generally excessively drained or well drained. Soils on steep, barren terrain are more prone to erosion than those on plains, or on vegetation-covered surfaces.
3) Climate: - Temperature, precipitation and frost action have a great influence on the soil forming processes which occur within a region. The kind of climate largely determines the nature and speed of the weathering processes. It directly affects the type of vegetation in an area which in turn will affect those soil forming processes related to vegetation. Temperature and precipitation govern the rate of chemical and physical weathering of the soils and allows for the accumulation of organic matter in the surface layer of the soils.
4) Biological Activity: - All living organisms actively influence the soil forming process. These organisms include bacteria, fungi, vegetation and animals. Their major influence is the effect on the chemical and physical environment of the soils. The roots of plants also hold the soils and protect them from wind and water erosion. They shelter the soils from the sun and other environmental conditions, helping the soils to retain the needed moisture for chemical and biological reactions.
5) Time: - Time describes an ongoing factor of soil formation. Soils can take many years to form. Younger soils have same characteristics from their parent material, but as they age, the addition of organic matter, exposure to moisture and other environmental factors may change its features. With time, they settle and are buried deeper below the surface, taking time to transform. Time is not always an indicator of the exact age of a soil or the stage of a soil’s development.

Question Bank

Q1. Differentiate between endogenic and exogenic forces.
Q2. Define the term aggredation/degradation/gradation.
Q3. Distinguish between geomorphic processes and geomorphic agents.
Q4. Explain the process of diastrophism.
Q5. What do you mean by denudation? - Explain with example.
Q6. "Endogenic and exogenic forces are changing the landforms on the earth surface" - Explain the statement with suitable example.
Q7. What is weathering? explain different types of weathering.
Q8. Differentiate between oxidation and carbonation.
Q9. What is mechanical weathering/physical weathering? What are the factors affecting the process of mechanical weathering?
Q10. Write a short note on exfoliation.
Q11. Explain the process of the formation of tors.
Q12. Explain the process of freezing, thawing and frost wedging.
Q13. What is biological weathering? explain with example.
Q14. Explain the significance of weathering.
Q15. What is mass movement? what are the factors help to increase the rate of mass movement?
Q16. Differentiate between slow and rapid mass movement with example.
Q17. Explain the factors for the formation of soil.