6. Geomorphic Processes

 NCERT Questions:

1. Multiple choice questions:

(i) Which one of the following processes is a gradual process?

a) Deposition

b) Diastrophism

c) Volcanism

d) Erosion

Ans. d) Erosion

(ii) Which one of the following materials is affected by hydration process?

a) Granite

b) Clay

c) Quartz

d) Salts

Ans. d) Salts

(iii) Debris avalanche can be included in the category of.

a) Landslides

b) Slow flow, mass movements

c) Rapid flow mass movements

d) Subsidence

Ans. a) Landslides

2. Answer the following questions in about 30 words:

(i) It is weathering that is responsible for biodiversity on the Earth. How?

Ans.

a) Weathering processes lead to breaking down the rocks into smaller fragments and preparing the way for formation of not only regolith and soils but also erosion and mass movements.

b) Biodiversity is basically a result of forests and vegetation.

c) Forests and vegetation depends upon the depth of weathering mantles.

d) Erosion cannot be significant if the rocks are not weathered.

e) It implies that weathering aids, mass wasting, erosion and reduction of relief and changes in landforms are a consequence of erosion.

 (ii) What are mass movements that are real, rapid and perceptible? List them.

Ans.

a) These movements transfer the mass of rock debris down the slopes under the direct influence of gravity.

b) That means air, water or ice do not carry debris with them from place to place but on the other hand, the debris may carry with it air, water or ice.

c) Mass movements can be slow or rapid. Rapid movements are mostly prevalent in humid climatic regions and occur over gentle to steep slopes.

d) When slopes are steeper, even the bedrock, especially of soft sedimentary rocks like shale or deeply weathered igneous rocks, may slide downslope.

(iii) What are the various mobile and mighty exogenic geomorphic agents and what is the prime job they perform?

Ans.

a) The exogenic processes derive their energy from atmosphere, determined by the ultimate energy from the sun and also the gradients created by tectonic factors.

b) All the exogenic geomorphic processes are covered under a general term denudation. The word ‘denude’ means to strip off or to uncover.

c) As there are different climatic regions on the Earth surface, the exogenous geomorphic processes vary from region to region. Temperature and precipitation are the two important climatic elements that control various processes.

d) Their prime job includes weathering, mass wasting movements, erosion and transportation.

(iv) Is weathering essential as a prerequisite in the formation of soils. Why?

Ans.

a) Yes, weathering is an essential prerequisite in the formation of soils.

b) Weathering is action of elements of weather and climate over Earth materials.

c) There are a number of processes within weathering which act either individually or together to affect the earth materials in order to reduce them to fragmental state.

d) Weathering is mechanical disintegration and chemical decomposition of rocks through the actions of various elements of weather and climate.

e) Weathering is an important process in the formation of soils. When rocks undergo weathering, rocks start to break and take form of soil gradually.

 Answer the following questions in about 150 words:

(i) Earth is a play field for two opposing groups of geomorphic processes. Discuss.

Ans.

a) It is absolutely right to say that our Earth is a play field for two opposite groups of forces. These forces are exogenic and endogenic.

b) The external forces are known as exogenic forces and the internal forces are known as endogenic forces.

c) The difference in the internal forces operating from within the Earth which built up the crust has been responsible for the variations in the outer surface of the crust. The Earth surface is being continuously subjected to external forces induced basically by energy. (Sunlight).

d) Of course, the internal forces are still active though with different intensities. That means the Earth surface is being continuously subjected to the external forces originating within the Earth’s atmosphere and by internal forces from within the Earth.

e) The actions of exogenic forces result in wearing down (degradation) of relief /elevations and filling up (aggradation) of basins/depressions on the Earth’s surface. The endogenic forces continuously elevate or build up parts of the earth surface and hence the exogenic processes fail to even out the relief variations of the surface of the earth. So variations remain as long as the opposite actions of exogenic and endogenic forces continue.

f) In general terms, the endogenic forces are mainly land building forces and the exogenic processes are mainly land wearing forces.

 (ii) Exogenic geomorphic processes derived their ultimate energy from the sun’s heat. Explain.

Ans.

a) The exogenic processes derived their energy from the atmosphere, determined by the ultimate energy from the sun and also the gradients created by tectonic factors.

b) Various minerals in rocks possess their own limits of expansion and contraction. With rise in temperature, every mineral expands and pushes against its neighbour, and as temperature falls a corresponding contraction takes place. Because of diurnal changes is the cause of splitting of individual grains within rocks which eventually fall off. This process of falling off individual grains may result in granular disintegration or granular foliation.

c) Salt crystallization is most effective of all salt weathering processes. In areas. With alternating wetting and drying conditions, salt crystal growth is favoured and the neighbouring grains are pushed aside.

d) Sodium chloride and gypsum crystals in desert areas heap up overlying layers of materials and with the result polygonal cracks develop all over the head surface. With salt crystal growth, chalk breaks down more readily. Followed by limestone, sandstone, shale. Gneiss, granite etc.

(iii) Are physical and chemical weathering processes independent of each other? If not, why? Explain with examples.

Ans.

a) No, physical and chemical weathering are not independent of each other. They are different, but still interdependent. Physical or mechanical weathering processes depend on some applied forces. The applied forces could be.

i) Gravitational forces such as overburden pressure load and shearing stress.

ii) Expansion forces due to temperature changes, crystal growth, or animal activity.

iii) Water pressure controlled by wetting and drying cycles.

b) Chemical weathering depends on a group of weathering processes. Solution carbonation, hydration, oxidation and reduction act on the rocks to decompose, dissolve, or reduce them to a fine plastic state through chemical reaction by oxygen, surface or soil, water and other acids.

i) Water and air, oxygen and carbon-dioxide along with heat must be present to speed up all chemical reactions.

ii) Over and above the carbon dioxide present in the air, decomposition of plants and animals increases the quantity of carbon dioxide underground. These chemical reactions on various minerals are very much similar to the chemical reactions in a laboratory.

iii) These forces are interdependent. For example, availability of water and heat depends on physical factors as well as chemical reactions.

(iv) How do you distinguish between the process of soil formation and soil forming factors? What is the role of climate and biological activity as two important control centers in the formation of soils?

Ans. Process referred to step by step procedure for methodical ways in which soil comes into existence while factors causing this formation are called soil forming factors. Soil formation processes:

Soil formation is called paedogenesis.

a) It depends on weathering the most.

b) The weathered material or transported deposits are colonised by bacteria and other inferior plant bodies like mosses and lichens.

c) Several minor organisms may take shelter within the mantle and deposits.

d) The dead remains of organism and plant help in humus accumulation.

e) Minor grasses and ferns may grow; later bushes and trees will start growing through seeds brought by birds and wind.

f) Plant roots penetrate down burrowing animals bring up particles, mass of materials become porous and sponge like with the capacity to retain water and to permit the passage of air and finally a mature soil is formed.

g) A complex mixture of mineral and organic products forms.

Five basic factors that control the formation of soils are:

i) Parent material

ii) Topography

iii) Climate

iv) Biological activity

v) Time

In fact, soil forming factors act in union and affect the action of one another.

Climate – Climate is an important active factor in soil formation. The climatic elements involved in soil development are moisture and temperature.

a) Precipitation gives soil its moisture content, which makes the chemical and biological activities possible. Excess of water helps in the downward transportation of soil components through the soil. (Eluviation) and deposits the same down below (illuviation).

b) Temperature acts in two ways, increasing or reducing chemical and biological activity. Chemical activity is increased in higher temperatures and reduced in cooler temperatures (with an exception of carbonation) and stops in freezing conditions.

c) That is why tropical soils with higher temperatures show deeper profiles, and in the frozen tundra regions, soils contain largely mechanically broken materials.

Biological activity – The vegetation cover and organisms that occupy the parent materials from the beginning and also at later stages help in adding organic matter, moisture retention, nitrogen, etc.

a) Dead plants provide humus. Some organic acids which form during humus formation aid in decomposing the minerals of the soil parent materials. Intensity of bacterial activity shows differences between soils of cold and warm climates.

b) Humus accumulates in cold climates as bacterial growth is slow.

c) With un-decomposed organic matter because of low bacterial activity layers of peat developed in sub-Arctic and tundra climate.

d) Rhizobium, a type of bacteria lives in the root nodules of leguminous plants and fixes nitrogen which is beneficial to the host plant.

e) The influence of large animals and insect ants, termite earthworm rodents etc. is mechanical, but it is nevertheless important in soil formation as they rework the soil up and down. In case of earthworms, as they feed on soil, the texture and chemistry of the soil that comes out of their body changes.

Question Bank:

Multiple choice questions:

1. An example of exogenic process is:

a) Fold

b) Fault

c) Volcanism

d) Weathering

Ans. d) Weathering

Exogenic processes are acting at the surface of the earth, primarily driven by solar energy. Weathering is an action of elements of weather and climate over the earth.

2. The expansion of the salt depends on:

a) Temperature

b) Hails

c) Atmospheric pressure

d) Winds

Ans. a) Temperature;

Salt expansion normally takes place in arid climates as strong heating causes strong evaporation; leading to its expansion. It is known as salt weathering.

3. Creep can occur under the category of:

a) Avalanches

b) Slow movement

c) Rapid movement

d) Landslide

Ans. b) Slow movement

In creep movement of material is particularly slow and barely visible except through extended observation.

4. Mudflow occurs frequently on the slopes of:

a) Mountains covered with vegetation

b) Plateau

c) Erupted volcanoes

d) Plains

Ans. c) Erupted volcanoes

Volcanoes ash, dust and other trash turn into mud due to intense rains and flow down as streams of mud.

5. Rapid rolling or sliding of earth debris without backward rotation of mass is known as:

a) Debris slide

b) Slump

c) Rockslide

d) Mudflow

Ans. Debris slide

Debris fall is nearly a free fall from vertical or over hanging place.

6. Denudation process like erosion and transportation are controlled by:

a) Mechanical energy

b) Electrical energy

c) Light energy

d) Kinetic energy

Ans. Kinetic energy is the energy of motion. Wherever it is high (fast water), a lot of erosion and transportation takes place and if it is low, deposition is there.

7. A type of bacteria that lives in the roots of leguminous plants is:

a) Bacillus subtilis

b) Cyanobacteria

c) Pseudomonas fluorescens

d) Rhizobium

Ans. d) Rhizobium

Rhizobium enters the roots of legumes either through root hair or directly at the point of emergence of lateral roots. Curling or controlled growth and branching of root hairs is the first visible plant response to rhizobium.

8. The difference between the soils of cold and warm climate is shown through the intensity of:

a) Bacterial activity

b) Its colour

c) Agriculture

d) Its horizon

Ans. Bacterial activity

Humus is high in cold climate as bacterial growth is slow. Whereas in hot climatic region, bacterial growth action is intense and dead vegetation is rapidly oxidised, leaving very low humus content in the soil.

9. Which is the force that continuously elevates or build up parts of the earth’s surface?

a) Exogenic forces

b) Endogenic forces

c) Gradation

d) Degradation

Ans. Endogenic forces

Endogenic forces are continuously building up the earth’s surface. The internal forces within earth are known as endogenic forces.

10. Solution, carbonation, hydration and reduction are the part of:

a) Mechanical weathering

b) Chemical weathering

c) Physiological weathering

d) Biological weathering

Ans. Chemical weathering

A group of weathering processes viz., solution, carbonation, hydration, oxidation and reduction act on the rocks to decompose, dissolve or reduce them to a fine clastic state through chemical reactions by oxygen, surface and/ or soil water and other acids. Water and air (oxygen and carbon dioxide) along with heat must be present to speed up all chemical reactions.

11. The capacity of rocks to allow water to pass through it is called:

a) Porosity

b) Wedging

c) Exfoliation

d) Hydration

Ans. Porosity

Porosity and permeability are two of the primary factors that control the movement and storage of fluids in rocks and sediments. They are intrinsic characteristics of these geologic materials. The exploitation of natural resources, such as groundwater and petroleum, is partly dependent on the properties of porosity and permeability.

12. All the movements either within or on the earth’s surface are caused due to:

a) Earthquakes

b) Gravity

c) Gradient

d) Plate tectonics

Ans. Gradient

All the movements are due to gradients from higher levels to lower levels, high pressure to low pressure areas etc.

13. Rock slides are more common over:

a) Horizontal slopes

b) Undulating surface

c) Gentle slopes

d) Steep slopes

Ans. d) Steep slopes

Sliding of an individual rock mass down bedding, joint or a fault surface is rockslide. Over steep slopes, rock sliding is very fast and destructive.

14. An endogenic geomorphic process is:

a) Volcanism

b) Mass wasting

c) Erosion

d) Weathering

Ans. a) Volcanism;

Diastrophism and volcanism are endogenic geomorphic process. Weathering, mass wasting, erosion and deposition are exogenic geomorphic processes.

15. The soil that has minimum humus content is:

a) Grey desert soil

b) Red desert soil

c) Chestnut soil

d) Chernozem

Ans. b) Red desert soil;

Any of a group of soils that develop in a warm, temperate, moist climate under deciduous of mixed forests, which has thin organic mineral layers overlying a yellowish leached layer has minimum humus content. Red soils generally form from iron rich sedimentary rock. They are generally poor growing soils, low in nutrients and humus and difficult to cultivate.

16. A geomorphic agent is:

a) Landslide

b) Volcano

c) Groundwater

d) Earthquake

Ans. c) Groundwater

Any Exogenic element of nature (like water, ice, wind, etc.) capable of acquiring and transporting earth’s material can be a geomorphic agent. Running water, groundwater, glaciers, wind, waves and currents etc., can be called geomorphic agents.

17. Which is the mineral involved in the process of oxidation?

a) Iron

b) Manganese

c) Sulphur

d) All the above

Ans. d) All the above

Oxidation means a combination of minerals with oxygen to oxides or hydroxides.

18. Which of the following is incorrect?

a) Fault and fold mountains – earth movements

b) Deltas and floodplains – fluvial effect

c) Coral reefs – glacial activity

d) Moraines – glacial activity

Ans. c) Coral reefs – glacial activity

Glacial activity; Coral reefs are formed due to the accumulation of calcareous organisms, found in marine waters containing few nutrients, in most reefs, the predominant organisms are stony corals that secrete an exoskeleton of calcium carbonate. The accumulation of skeletal material, broken and piled up by wave action, bio-erodes and produces a calcareous formation that supports the living corals and a great variety of other animal and plant life. Coral reefs most commonly live in tropical waters, but deep water and cold water corals exist on a much smaller scale.

19. Which of the following is not true?

a) Formation of V-shaped valley is not a characteristics of youthful topography

b) Maximum erosion characterises mature stage topography

c) Plateau is a landform of mature stage topography

d) Delta is a feature of old age topography

Ans. a) Formation of V-shaped valley is not a characteristic of youthful topography

V-shaped valleys are formed in the upper course where the river channel is narrow and fast flowing.

20. Hydration process affects:

a) Granite

b) Clay

c) Quartz

d) Salt

Ans. d) Salt

Hydration is the chemical addition of water. Minerals take up water and expand; this expansion causes an increase in the volume of the mineral itself or rock. Many clay minerals swell and contract during wetting and drying, and a repetition of this process result cracking of overlying materials. Salts in pore spaces undergo rapid and repeated hydration and help in rocks fracturing.

21. The reaction of carbonate and bicarbonate with minerals is called:

a) Oxidation

b) Foliation

c) Hydration

d) Carbonation

Ans. d) Carbonation

Carbonation is the reaction of carbonate and bicarbonate with minerals and is a common process helping the breaking down of feldspars and carbonate minerals.

22. Exfoliation domes result due to:

a) Salt weathering

b) Flaking off

c) Thermal contraction

d) Thermal expansion

Ans. d) Thermal expansion

Removal of overlying rock load because of continued erosion causes vertical pressure release with the result that the upper layers of the rock expand producing disintegration of rock masses. Exfoliation domes and tors result due to unloading and thermal expansion respectively.

23. Expansion of salts depends on:

a) Thermal properties

b) Size

c) Physical properties

d) Density

Ans. a) Thermal properties

Many of the salts like calcium, sodium, magnesium, potassium and barium have a tendency to expand. Expansion of these salts depends on temperature and their thermal properties.

24. Glacial are subject to:

a) Frost weathering

b) Folding

c) Frost wedging

d) Faulting

Ans. c) Frost wedging

Glacial areas are subject to frost wedging daily. In this process, the rate of freezing is important. Rapid freezing of water causes its sudden expansion and high pressure. The resulting expansion affects joints; cracks and small inter granular fractures to become wider till the rock breaks apart.

25. Orogeny is a:

a) Crust building process

b) Ocean building process

c) Continental building process

d) Mountain building process

Ans. d) Mountain building process

Orogeny is a mountain building process whereas Epeirogeny is a continental building process.

26. Slow downslope flowing soil mass saturated with water is called:

a) Lithification

b) Denudation

c) Solifluction

d) Foliation

Ans. c) Solifluction

Solifluction involves slow downslope flowing soil mass or fine grained rock debris saturated or lubricated with water. This process is quite common in moist temperate areas where surface melting of deeply frozen ground and long continued rain, occur frequently.

27. Aeration of the soil is helped by:

a) Micro fauna

b) Mesofauna

c) Macro fauna

d) Flora

Ans. b) Mesofauna

Mesofauna comprises worm like animals. They help in aeration and mixing minerals and organic matter.

28. Which one of the following is false?

a) Destruction activities of waves produce sea cliffs

b) Depositional activity of wind produces loess plains and sand dunes

c) Destruction activity of soil movement produces landslide movements

d) Construction activity of soil movement produces landslide movement

Ans. Construction activity of soil movement produces landslide movement

The action of gravity is the primary driving force for a landslide to occur, there are other contributing factors affecting the original slope stability. Typically, pre-conditional factors build up specific sub- surface conditions that make the area/ slope prone to failure, whereas the actual landslide often requires a trigger before being released.

29. Debris avalanche can be included in the category of:

a) Landslide

b) Rapid flow mass movement

c) Slow flow mass movement

d) Subsidence

Ans. b) Rapid flow mass movement

Debris avalanche is characteristic of humid regions with or without vegetation cover and occurs in narrow tracks on steep slopes. A debris avalanche is formed when unstable slope collapse and debris is transported away from the slope. This debris avalanche can be much faster than the mudflow. Large scale avalanches normally occur on very steep volcanoes. Debris avalanche is similar to snow avalanche.

30. Rapid rolling or sliding of earth debris without backward rotation of mass is known as:

a) Flow

b) Rock slide

c) Slump

d) Debris slide

Ans. d) Debris slide

Slump is slipping of one or several units of rock debris with a backward rotation with respect to the slope over which the movement takes place. Rapid rolling or sliding of earth debris without backward rotation of mass is known as debris slide.

31. A slow mass movement is:

a) Creep

b) Earth flow

c) Mud flow

d) Slump

Ans. a) Creep

Creep can occur on moderately steep, soil covered slopes. Movement of material is extremely slow and imperceptible except through extended observation. Materials involves can be soil or rock debris.

32. A pedologist is a:

a) Rock scientist

b) Mineral scientist

c) Soil scientist

d) Nuclear scientist

Ans. c) Soil scientist

Pedology is soil science. A pedologist is a soil scientist.

33. Weathering is an important process in the formation of:

a) Rocks

b) Soils

c) Stones

d) Minerals

Ans. b) Soils

Weathering is defined as mechanical disintegration and chemical decomposition of rocks through the actions of various elements of weather and climate.

34. Deposition is a consequence of:

a) Leaching

b) Erosion

c) Weathering

d) Bleaching

Ans. b) Erosion

Deposition is a consequence of erosion. The erosional agents loose the velocity; hence, deposit on gentler slopes and the materials carried by them start to settle themselves.

35. The agent of erosion that is unaffected by climate:

a) Wind

b) Groundwater

c) Water

d) Ice

Ans. b) Groundwater

The work of other two agents of erosion-waves and ground water is not controlled by climate. In case of waves, it is the location along the interface of lithosphere and hydrosphere coastal region that will determine the work of waves, whereas the work of ground water is determined more by the lithological character of the region.

36. Slump is ________.

a) Slipping of rock debris with a backward rotation

b) Slipping of rocks without backward rotation

c) Sliding of rock masses down the bedding

d) None

Ans. a) Slipping of rocks with backward rotation

Slump is slipping of one or several units of rock debris with a backward rotation with respect to the slope over which the movement takes place.

37. Which one of the following is not included in landslide?

a) Slump

b) Debris slide

c) Rock slide

d) All are included

Ans. d) All are included

Landslides are relatively rapid and perceptible movements. The materials involved are relatively dry. Slump is slipping of one or several units of rock debris with a backward rotation with respect to the slope over which the movement takes place. Rapid rolling or sliding of earth debris without backward rotation of mass is known as debris slide. Sliding of individual rock masses down bedding joint or fault surface is rockslide.

38. Which one of the following is not a slow mass movement?

a) Creep

b) Solifluction

c) Mud flow

d) All

Ans. c) Mud flow

Mud flow occurs frequently on the slopes of erupting or recently erupted volcanoes. Volcanic ash, dust and other fragments turn into mud due to heavy rains and flow down as tongues or streams of mud causing great destruction to human habitations.

39. Which one of the following is not a form of mass movement?

a) Flow

b) Slide

c) Slumping

d) Expansion

Ans. d) Expansion

Landslide, flows, slump, falls are mass movement. Mass wasting may occur at a very slow rate, particularly in areas that are very dry or those areas that receive sufficient rainfall such that vegetation has stabilized the surface.

40. What is mass movement?

a) Movement of people at a large scale

b) The movement which transfers rock debris down to the slopes

c) Movement of animals

d) All

Ans. b) The movement which transfers rock debris down to the slopes

Mass wasting, also known as mass movement , is the geomorphic process by which soil, sand, regolith and rock move downslope typically as a mass, largely under the force of gravity but frequently affected by water and water content as in submarine environments and mudslides.

41. The capacity of rocks to allow water to pass through it is called _____.

a) Porosity

b) Permeability

c) Jointing

d) Hardness

Ans. a) Porosity

Porosity is a measure of how much of a rock has open space. This space can be between grains or within cracks or cavities of the rock. Permeability is a measure of the ease with which water can move through a porous rock.

42. The most important determinant of resistance of rocks to weathering is _____.

a) Hardness

b) Jointing

c) Permeability

d) Cracks

Ans. a) Hardness

Among the rock characteristics influencing frost weathering, the most determinant ones are the rock specific surface area, permeability, porosity etc.

Porosity: is a measure of the void spaces in a material.

Permeability: is a measure of the ability of a material (such as rocks) to transmit fluids. Porosity and permeability are related properties of any rock or loose sediment. Both are related to the number, size and connections of openings in the rock.

43. Weathering is an important process in the formation of ________.

a) Rocks

b) Soils

c) Stones

d) Valleys

Ans. b) Soils

Weathering is simply the chemical and/ or physical breakdown of a rock material. It involves specific processes, acting on rock materials at or near the surface of the earth; weathering is an important process in the formation of soil.

44. Exfoliation refers to:

a) Weathering of rocks

b) Weathering of rocks by the action of animals

c) Peeling away of sheets of rock

d) None

Ans. c) Peeling away of sheets of rock

Exfoliation is the term used to describe the peeling away of sheets of rock millimetres to meters in thickness from rock’s surface due to a range of physical and chemical processes during exfoliation and weathering.

45. Where is frost wedging a common feature?

a) Riverine lands

b) Glaciated lands

c) Arid lands

d) Hot and humid areas

Ans. b) Glaciated lands

Glacial areas are subject to frost wedging daily. In this process, the rate of freezing is important. Rapid freezing of water causes its sudden expansion and high pressure.

46. Solution, carbonation, hydration and reduction are the part of ________.

a) Mechanical weathering

b) Chemical weathering

c) Physiological weathering

d) Not a type of weathering

Ans. b) Chemical weathering

A group of weathering processes viz., solution, carbonation, hydration, oxidation and reduction act on the rocks to decompose, dissolve or reduce them to a fine clastic state through chemical reactions by oxygen, surface and or soil water and other acids.

47. In weathering __________.

a) No motion of material takes place

b) Materials move from one place to another

c) The deposition of material takes place

d) None of the above

Ans. a) No motion of material takes place

Weathering is in-situ or on-site process. Very little or no motion of material takes place in weathering.

48. Weathering can be defined as _______.

a) Mechanical disintegration of rocks

b) Disintegration and deformation of rocks with the help of climate factors

c) Chemical decomposition of rocks

d) All the above

Ans. d) All the above;

Weathering is defined as mechanical disintegration and chemical decomposition of rocks through the actions of various elements of weather and climate.

49. Which one of the following is a degradation process?

a) Deposition

b) Volcanism

c) Diastrophism

d) Erosion

Ans. d) Erosion

Weathering, mass-wasting and erosion are degradation processes. It is erosion that is largely responsible for continuous changes that the earth’s surface is undergoing.

50. Soil profile refers to ______.

a) Its horizontal layers

b) Vertical section of the soil from the ground surface downwards

c) Groups of soil grain

d) None of the above

Ans. b) Vertical section of the soil from the ground surface downwards

The soil profile is defined as a vertical section of the soil from the ground surface downwards to where soil meets the underlying parent rock.

51. Mass movement is favoured by ________.

a) Torrential and abundant rain

b) Steep slope

c) Steeply dipping slopes

d) All the above

Ans. d) All the above

All weak unconsolidated materials, thinly bedded rocks, faults, steeply dipping beds, vertical cliffs or steep slopes, abundant precipitation and torrential rains and scarcity of vegetation etc. favour mass movement.

Short answer type questions:

 What is diastrophism?

Ans. All processes that move, elevate or build up portions of earth’s crust come under diastrophism.

2. What is epeirogenesis process?

Ans. These are the processes involve uplift or warping of large parts of the earth’s crust.

3. What is the difference between Orogeny and Epeirogeny?

Ans. Orogeny is a mountain building process whereas Epeirogeny is continental building process.

4. What is denudation?

Ans. All the Exogenic processes are collectively termed as denudation. The word ‘denude’ means to strip off or to uncover. Weathering, mass wasting, erosion and transportation are included in it.

5. What is weathering?

Ans. It is an Exogenic process. It is the mechanical disintegration of rocks through the action of various elements of weather and climate.

6. What is mass wasting?

Ans. Mass wasting is the geomorphic process by which soil, regolith and rock move downslope, largely under the force of gravity, but frequently affected by water and water content as in submarine environment and mudslides.

7. What is desilication?

Ans. Removing of silica from soil is known as desilication.

8. What is humus?

Ans. The decomposition of plants as micro -organisms release organic chemicals that interact with the loose materials called humus. It is the dead organic matter in the soil.

9. What is geomorphology?

Ans. Geomorphology is devoted to the study of landforms, their evolution and related processes.

10. Define earth flow.

Ans. In the mountainous regions of humid climate, water saturated clayey or silt earth materials slide down low angle terraces or hillsides is known as earth flow. It is a form of mass wasting.

11. What is pedology?

Ans. Pedology is soil science. A pedologist is a soil scientist.

12. What is a solution?

Ans. When something is dissolved in water or acids, the water or acid with dissolved contents is called solution. This process involves removal of solids in solution and it depends upon solubility of a mineral in water or weak acids.

13. Define slump.

Ans. Slump is slipping of single or several units of rock debris with a backward rotation with respect to the slope over which the movement takes place.

14. Define debris slide and rock slide.

Ans. Debris: rapid rolling or sliding of earth debris without backward rotation of mass is known as debris slide

Rock slide: sliding of individual rock masses down bedding, joint or fault surfaces is known as rock slide.

15. Differentiate between chemical and mechanical weathering.

Ans.

16. What are geomorphic agents?

Ans. An agent is a mobile medium (like running water, moving ice, wind, waves and currents, etc.) which removes, transports and deposits earth’s materials. Running water, ground water, glaciers, wind, waves and currents etc. can be called geomorphic agents.

17. Define hydration.

Ans. Hydration is the chemical addition of water. Minerals take up water and expand. This expansion causes an increase in the volume of the material itself or rock. Calcium sulphate takes in water and turns to gypsum. It is a reversible process. The volume changes in minerals due to hydration will also help in physical weathering through exfoliation and granular disintegration.

18. What is the significance of weathering?

Ans.

1. a) Weathering is an important process in the formation of soil.
2. b) Weathering aids mass wasting, erosion and reduction of relief and changes in landforms are a consequence of erosion.
3. c) Weathering of rocks and deposits helps in enrichment and concentrations of certain valuable ores of iron, manganese, aluminium, copper etc. which are of great importance for the nation.

19. Explain the process of soil formation.

Ans. Weathering plays a pivotal role in the formation of soils. Weathering material is the basic input for soil to form. Transported deposits are occupied by bacteria and plant bodies, like mosses and lichens. The dead remains of organisms and plants help in humus accumulation. Seeds brought by birds and wind result in the growth of grasses, ferns, bushes and trees. Plant roots penetrate down. Burrowing animals bring up particles. Further mass of material becomes porous and sponge-like with a capacity to retain water and to permit the passage of air and finally a mature soil, a complex mixture of mineral and organic product forms.