DENTRITIC PATTERN


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CHAPTER -3 INDIA- DRAINAGE SYSTEM (BOOK II )

DRAINAGE SYSTEM

1. Define

Drainage :The flow of water through well-defined channels is known as ‘drainage’

Drainage system :The  network of well defined channels through which water flows  is called a ‘drainage system’.

Catchment area  : A river drains the water collected from a specific area,  is called its ‘catchment area’

Drainage Basin :  An area drained by a river and its tributaries is called a drainage basin

Water divide : . The boundary line separating one drainage basin from the other is known as the water divide

River basins  and Wtaer shed : . The catchments of large rivers are called river basins while those

of small rivulets and rills are often referred to as watersheds.

Watersheds are small in area while the basins cover larger areas.

2. What are the factors affecting the the drainage pattern of an area ?

 The drainage pattern of an area is the outcome of the geological time period, nature and structure of rocks, topography, slope, amount of water flowing and the periodicity of the flow.

3. What are the different drainage patterns formed by the rivers ? Explain

(i) The drainage pattern resembling the branches of a tree is known as “dendritic” the examples

of which are the rivers of northern plain.

(ii) When the rivers originate from a hill and flow in all directions, the drainage pattern is known

as ‘radial’. The rivers originating from the Amarkantak range present a good example of it.

(iii) When the primary tributaries of rivers flow parallel to each other and secondary tributaries

join them at right angles, the pattern is known as ‘trellis’.

(iv) When the rivers discharge their waters from all directions in a lake or depression, the

pattern is known as ‘centripetal’.

4. Classify Indian river system on the basis of discharge of water or orientations to the sea

On the basis of discharge of water (orientations to the sea), it may be grouped into:(i) the Arabian Sea drainage; and (ii) the Bay of Bengal drainage. They are separated from each other through the Delhi ridge, the Aravalis and the Sahyadris

Nearly 77 per cent of the drainage area consisting of the Ganga, the Brahmaputra, the Mahanadi, the Krishna, etc. is oriented towards the Bay of Bengal while 23 per cent comprising the Indus, the Narmada, the Tapi, the Mahi and the Periyar systems discharge their waters in the Arabian Sea.

5. Classify Indian river system on the basis of the size of the watershed,he drainage basins

: (i) Major river basins with more than 20,000 sq. km of catchment area.

It includes 14 drainage basins such as the Ganga, the Brahmaputra, the Krishna, theTapi, the Narmada, the Mahi, the Pennar, the Sabarmati, the Barak, etc.

(ii) Medium river basins with catchment area between 2,000-20,000 sq. km incorporating 44 river basins such as the Kalindi, the Periyar, the Meghna, etc.

 (iii) Minor river basins with catchment area of less than 2,000 sq. km include fairly good number of rivers flowing in the area of low rainfall.

6. Classify Indian river system on the basis of  the mode of origin, nature and characteristics,

Ans :  The Himalayan drainage and the Peninsular drainage.

7.State the characteristic features of the Himalayan drainage  

  1. These are fed both by melting of snow and precipitation,

  2. They  are perennial.

  3. These rivers pass through the giant gorges carved out by the erosional activity carried on simultaneously

      with the uplift of the Himalayas.

   4. Besides deep gorges, these rivers also form V-shaped valleys, rapids and waterfalls in their mountainous

       course.

   5.In the plains, they form depositional features like flat valleys, ox-bow lakes, flood plains, braided       

      channels, and deltas near the river mouth.

6. They also  display a strong meandering tendency and shift their  courses frequently.

8. Which river is known as the sorrow of Bihar and Why ?

River Kosi, is known  as the ‘sorrow of Bihar’, because it causes severe damage to the life and property of the people due to flood.

9.Describe the evolution of the Himalayan Rivers.

Geologists believe that a mighty river called Shiwalik or Indo-Brahma traversed the entire longitudinal extent of the Himalaya from Assam to Punjab and onwards to Sind, and finally discharged into the Gulf of Sind near lower Punjab during the Miocene period some 5-24 million years ago

The remarkable continuity of the Shiwalik and its lacustrine origin and alluvial deposits  consisting of sands, silt, clay, boulders and conglomerates support this viewpoint.

It is opined that in due course of time Indo–Brahma river was dismembered into three main drainage systems: (i) the Indus and its five tributaries in the western part; (ii) the Ganga and its Himalayan tributaries in the central part; and (iii) the stretch of the Brahmaputra in Assam and its Himalayan tributaries in the

eastern part.

The dismemberment was probably due to the Pleistocene upheaval in the western Himalayas, including the uplift of the Potwar Plateau (Delhi Ridge), which acted as the water divide between the Indus and Ganga drainage systems. Likewise, the downthrusting of the Malda gap area between the Rajmahal hills and the Meghalaya plateau during the mid-pleistocene period, diverted the Ganga and the Brahmaputra systems to flow towards the Bay of Bengal

10. What are the probable reasons for the dismemberment of the Indo-Brahm ?

The dismemberment was probably due to  :

1. the Pleistocene upheaval in the western Himalayas, including the uplift of the Potwar Plateau (Delhi Ridge), which acted as the water divide between the Indus and Ganga drainage systems.
2. The downthrusting of the Malda gap area between the Rajmahal hills and the Meghalaya plateau during the mid-pleistocene period, diverted the Ganga and the Brahmaputra systems to flow towards the Bay of Bengal

11. Which are the three main drainage system formed by the dismemberment of Indo-Brahm ?

(i)                  The Indus and its five tributaries in the western part;

(ii)                The Ganga and its Himalayan tributaries in the central part;

(iii)               The stretch of the Brahmaputra in Assam and its Himalayan tributaries in the eastern part.

12  State the characteristic features of the Peninsular rivers

      1. The Peninsular drainage system is older than the Himalayan one.

      2.  They are fed by the rain only.

3. They have broad, largely-graded shallow valleys,
4. They are characterised by fixed course, absence of meanders
5. They are non perennial
6. They do not form deep gorges

13    Name the peninsular rivers flowing westward

River Narmada, River Tapi

14 Which relief feature of the peninsular plateau  forms the waterdivide between the rivers flowing to the Bay of Bengal and the Arabian Sea. ?

Ans : Wester Ghats

15 Descibe the three geological events believed to have been responsible for the evolution of the Peninsular drainage .

Three major geological events in the distant past have shaped the present drainage systems of Peninsular India:

 (i) Subsidence of the western flank of the Peninsula leading to its submergence below the sea during the early tertiary period. Generally, it has disturbed the symmetrical plan of the river on either side of the original watershed.

(ii) Upheaval of the Himalayas when the northern flank of the Peninsular block was subjected to subsidence and the consequent trough faulting. The Narmada and The Tapi flow in trough faults and fill the original

cracks with their detritus materials. Hence,there is a lack of alluvial and deltaic deposits in these rivers.

(iii) Slight tilting of the Peninsular block from northwest to the southeastern direction gave orientation to the

entire drainage system towards the Bay of Bengal

16 Define River Regime

The pattern of flow of water in a river channel over a year is known as its regime.

17 Describe the River regimes of the Himalayan and  the Peninsular rivers.

The north Indian rivers originating from the Himalayas are perennial as they are fed by glaciers through

snow melt and also receive rainfall water during rainy season.

The rivers of South India do not originate from glaciers and their flow pattern witnesses fluctuations.

The flow increases considerably during monsoon rains. Thus, the regime of the rivers of South India is controlled

by rainfall which also varies from one part of the Peninsular plateau to the other.

The discharge is the volume of water flowing in a river measured over time. It is measured either in cusecs (cubic feet per second) or cumecs (cubic metres per second).

The Ganga has its minimum flow during the January-June period. The maximum flow is attained either in August or in September.After September, there is a steady fall in the flow. The river, thus, has a monsoon regime during the rainy season.

There are striking differences in the river regimes in the eastern and the western parts of the Ganga Basin. The Ganga maintains a sizeable flow in the early part of summer due to snow melt before the monsoon rains begin.

The mean maximum discharge of the Ganga at Farakka is about 55,000 cusecs while the mean minimum is only 1,300 cusecs.

The two Peninsular rivers display interesting differences in their regimes compared to the Himalayan rivers. The

Narmada has a very low volume of discharge from January to July but it suddenly rises in August when the maximum flow is attained. The fall in October is as spectacular as the rise in August. The flow of water in the Narmada, as recorded at Garudeshwar, shows that the maximum flow is of the order of 2,300 cusecs, while the minimum flow is only 15 cusecs.

The Godavari has the minimum discharge in May, and the maximum in July-August. After August, there is a sharp fall in water flow although the volume of flow in October and November is higher than that in any of the months from January to May. The mean maximum discharge of the Godavari at Polavaram is 3,200 cusecs while the mean minimum flow is only 50 cusecs.. 

INDIA-CHAPTER -2 STRUCTURE&PHYSIOGRAPHY Contd..........

10.     Which are the four divisions of northern plain from north to south  .Explain

From the north to the south, these can be divided into three major zones: the Bhabar, the Tarai and the alluvial plains. The alluvial plains can be  further divided into the Khadar and the Bhangar.

Bhabar is a narrow belt ranging between 8-10 km parallel to the Shiwalik foothills at

the break-up of the slope. As a result of this,the streams and rivers coming from the

mountains deposit heavy materials of rocks and boulders, and at times, disappear in this

zone.

TARAI BELT  South of the Bhabar is the Tarai belt,with an approximate width of 10-20 km where most of the streams and rivers re-emerge without having any properly demarcated

channel, thereby, creating marshy and swampy conditions known as the Tarai. This

has a luxurious growth of natural vegetation and houses a varied wild life.

ALLUVIAL PLAIN

The south of Tarai is a belt consisting of old and new alluvial deposits known as the

Bhangar and Khadar respectively. These plains have characteristic features of mature

stage of fluvial erosional and depositional landforms such as sand bars, meanders, oxbow

lakes and braided channels. The Brahmaputra plains are known for their riverine islands and sand bars. Most of these areas are subjected to periodic floods and shifting river courses forming braided streams.

10 Which are the three  divisions of peninsular plateau ?

On the basis of the prominent relief features, the Peninsular plateau can be divided

into three broad groups:

(i) The Deccan Plateau

(ii) The Central Highlands

(iii) The Northeastern Plateau.

11. Which is the highest peak of peninsular India ?

‘Anaimudi’ (2,695 m),

12 Where does Eastern and Western ghats meet ?

The Eastern and the Western Ghats meet each other at the Nilgiri hills.

14 Which are the divisions of the Meghalaya Plateau ?

The Meghalaya plateau is further sub-divided into three: (i) The Garo Hills; (ii) The Khasi Hills; (iii) The Jaintia Hills,

15. Which is the important river of the Desert region ?

The Luni river flowing in the southern part of the desert

16 Classify the coastal plains on the basis of the location and active geomorphological processes, it can be broadly divided into two: (i) the western coastal plains; (ii) the eastern coastal plains

13 Differenciate between western and Eastern ghats

Western ghats	Eastern ghats
1. Western Ghats are comparatively higher in elevation 2. more continuous than the Eastern Ghats 3. Most of the Peninsular rivers have their origin in the Western Ghats 4. Theiraverage elevation is about 1,500 m with the height increasing from north to south	1. Eastern Ghats comprises low hills 2. They are discontinuous 3 These are highly eroded by the rivers such as the Mahanadi, the Godavari, the Krishna, the Kaveri, etc 4. Some of the important ranges include the Javadi hills,the Palconda range, the Nallamala hills, the Mahendragiri hills, etc

17 Differenciate between Western and Eastern Coastal Plain

Western Coastal Plain

Eastern Coastal Plain

The western coastal plains are an example  of submerged coastal plain it is a narrow belt provides natural conditions for the     development of ports and harbours   Extend from the Gujarat coast      in the north to the Kerala coast in                  the south The rivers flowing through this coastal plain do not form any delta the western coast may be divided into following divisions – the Kachchh and Kathiawar coast in Gujarat, Konkan coast in Maharashtra, Goan coast and Malabar coast in Karnataka and Kerala respectively

The eastern coastal plain is is an example of an emergent coast. The eastern coastal plain is Broader 3. Because of its emergent nature, it has less number of ports and harbours. 4. Extends from West Bengal in the north to Tamil Nadu in the south 5. There are well developed deltas here, formed by the rivers flowing eastward in to the Bay of Bengal 6.Eastern coast may be divided in to two Coromondel coast in South and Northern circar in the north

18. Differenciate between the island groups of Bay of Bengal and the Arabian Sea .

The Bay of Bengal island (Andaman and Nicobar Islands )

The islands of the Arabian sea (Lakshadweep Islands)

1 The Bay of Bengal island groups consist of about 572 islands/islets 2.These are situated roughly between 6°N-14°N and 92°E -94°E 3. The two principal groups of islets include the Ritchie’s archipelago and the Labrynth island 4. It is believed that these islands are an elevated portion of submarine mountains. 5. Barren island, the only active volcano in India is also situated in the Nicobar islands. 6. Island group are separated in to two by a water body which is called the Ten degree channel Andaman in the north and the Nicobar in the south

1. The islands of the Arabian sea include Lakshadweep and Minicoy. 2.  These are scattered between 8°N-12°N and 71°E -74°E longitude. 3.These islands are located at a distance of 280 km-480 km off the Kerala coast 4. The entire island group is built of coral deposits. 5.There are approximately 36 islands of which 11 are inhabited. Minicoy is the largest island with an area of 453 sq. km. 6. The entire group of islands is broadly divided by the Eleventh degree channel, north of which is the Amini Island and to the south of the Canannore Island.

19 Which type of rainfall is experienced in Andaman and Nicobar islands?

These islands receive convectional rainfall

20 What type of vegetation is found in Andaman and Nicobar islands?

These islands have an equatorial type of vegetation.

BOOK - II CHAPTER -2 INDIA-STRUCTURE &PHYSIOGRAHY

BOOK II

Chapter 2

INDIA  

STRUCTURE AND PHYSIOGRAPHY

1. Which are the physiographic divisions of  of India ?

India can be divided into the following physiographic divisions:

(i) The Northern and Northeastern Mountains

(ii) The Northern Plain

(iii) The Peninsular Plateau

(iv) The Indian Desert

(v) The Coastal Plains

(vi) The Islands

2.Which are the physiographic features forming The North and Northeastern Mountains

The North and Northeastern Mountains consist of   the  Himalayas and the Northeastern hills.

3. Which are the different ranges of Himalayas ?

The Himalayas consist of a series of parallel mountain ranges.

Some of the important ranges are

1. the Greater Himalayan range, which includes the Great Himalayas and the Trans-Himalayan range,
2.  the Middle Himalayas and
3.  the Shiwalik.

4. Which are the three Himalayan range explain each one of them

   1. the Great Himalayan range

The approximate length of the Great Himalayan range, also known as the central axial range, is 2,500 km from east to west, and their width varies between 160-400 km from north to south.

 It is also evident from the map that the Himalayas stand almost like a strong and long wall between the Indian subcontinent and the Central and East Asian countries

The northern most range is known as the Great or Inner Himalayas or the .Himadri.. It is the most continuous range consisting of the loftiest peaks with an average height of 6,000 metres. It contains all the prominent Himalayan peaks.

The core of this part of Himalayas is composed of granite. It is perennially snow bound, and a number of glaciers descend from this range.

    2. Middle himalaya

The range lying to the south of the Himadri forms the most rugged mountain system and

is known as Himachal or lesser Himalaya.

The ranges are mainly composed of highly compressed and altered rocks.

The altitude varies between 3,700 and 4,500 metres and the average width is of 50 Km.

While the Pir Panjal range forms the longest and the most important range, the Dhaula Dhar and the Mahabharat ranges are also prominent ones.

This range consists of the famous valley of Kashmir, the Kangra and Kullu Valley in Himachal Pradesh. This region is well known for its hill stations

3 .  Shiwalik range

The outer most range of the Himalayas is called the Shiwaliks. /Outer Himalayas

They extend over width of 10-50 Km and have an altitude varying between 900 and 1100 metres.These ranges are composed of unconsolidated sediments brought down by rivers from the main Himalayan ranges located farther north. These valleys are covered with thick gravel and alluvium.

1. What are  Karewas ? Karewas are the thick deposits of glacial clay and other materials embedded with moraines. 2. From where did the word  Shiwalik originate ? The word shiwalik has its origin in the geological formation found in and around a place called Sivawala near Dehra Dun which was once a headquarter of the Imperial Survey and which subsequently established its permanent headquarters at Dehra Dun .3 What are Duns ? give examples of it . The longitudinal valley lying between lesser Himalaya and the Shiwaliks are known as Duns. Dehra Dun, Kotli Dun and Patli Dun are some of the well-known Duns. . DehraDun is the largest of all the duns

5 Classify Himalayas on the basis of relief,alignment of ranges and other geomorphological features,

the Himalayas can be divided into the following sub-divisions,

(i) Kashmir or Northwestern Himalayas

(ii) Himachal and Uttaranchal Himalayas

(iii) Darjiling and Sikkim Himalayas

(iv) Arunachal Himalayas

(v) Eastern Hills and Mountains

6. Mention any ten characteristic features of Kashmir Himalayas

Kashmir or Northwestern Himalayas

1.It comprise a series of ranges such as the Karakoram, Ladakh, Zaskar and Pir Panjal.

2. The northeastern part of the Kashmir Himalayas is a cold desert, which lies between the Greater Himalayas and the Karakoram ranges.

3.  Between the Great Himalayas and the Pir Panjal range, lies the world famous valley of Kashmir and the famous Dal Lake.

4. Important glaciers of South Asia such as the Baltoro and Siachen are also found in this region. The Kashmir Himalayas are also famous for Karewa formations,

5.Some of the important passes of the region are Zoji La on the Great Himalayas,Banihal on the Pir Panjal,Photu La on the Zaskar and Khardung La on the Ladakh range.

6. Some of the important fresh water lakes are Dal and Wular

7.. This region is drained by the river Indus, and its tributaries such as the Jhelum and the Chenab.

8.Vaishno Devi, Amarnath Cave, Charar -e-Sharif,etc. are also located here and large number of  pilgrims visit these places every year

9. Srinagar, capital city of the state of Jammu and Kashmir is located on the banks of Jhelum river.

10. Dal Lake in Srinagar presents an interesting physical feature.

11. The southernmost part of this region consists of longitudinal valleys known as ‘duns’. Jammu dun and Pathankot dun are important examples

7. State the characteristic features of Himachal Himalayas

1.This part lies approximately between the Ravi in the west and the Kali (a tributary of

Ghaghara) in the east.

2.  It is drained by two major river systems of India, i.e. the Indus and the Ganga.

Tributaries of the Indus include the river Ravi, the Beas and the Satluj, and the

tributaries of Ganga flowing through this region include the Yamuna and the Ghaghara.

3. The northernmost part of the Himachal Himalayas is an extension of the Ladakh cold

desert, which lies in the Spiti subdivision of district Lahul and Spiti.

4. All the three ranges of Himalayas are prominent in this section also.

These are the Great Himalayan range, the Lesser Himalayas (which is locally known as

Dhaoladhar in Himachal Pradesh and Nagtibha in Uttaranchal) and the Shiwalik range from the North to the South.

 5. In this section of Lesser Himalayas, the altitude between 1,000-2,000 m specially attracted to the British colonial administration, and subsequently, some of the important hill stations such as Dharamshala,Mussoorie, Shimla, Kaosani and the cantonment towns and health resorts such as Shimla, Mussoorie, Kasauli, Almora,Lansdowne and Ranikhet, etc. were developed

in this region.

8. The two distinguishing features of this region from the point of view of physiography

are the ‘Shiwalik’ and ‘Dun formations’. Some important duns located in this region are the Chandigarh-Kalka dun, Nalagarh dun, Dehra Dun, Harike dun and the Kota dun, etc.

 7. DehraDun is the largest of all the duns with an approximate length of 35-45 km and a width of 22-25 km.

.8. The famous ‘Valley of flowers’ is also situated in this region.

9. The places of pilgrimage such as the Gangotri, Yamunotri, Kedarnath, Badrinath and Hemkund Sahib are also situated in this part. The region is also known to have five famous Prayags (river confluences)

9. Describe the features of The Darjiling and Sikkim Himalayas

1. They are flanked by Nepal Himalayas in the west and Bhutan Himalayas in the east.

 2. It is relatively small but is a most significant part of the Himalayas. Known for its fast-flowing rivers such as Tista, it is a region of high mountain peaks like Kanchenjunga (Kanchengiri), and deep valleys.

3. The higher reaches of this region are inhabited by Lepcha tribes while the southern part, particularly the Darjiling Himalayas, has a mixed population of Nepalis, Bengalis and tribals from Central India.

4. The British, taking advantage of the physical conditions such as moderate slope,

thick soil cover with high organic content, well distributed rainfall throughout the year and

mild winters, introduced tea plantations in this region.

5. As compared to the other sections of the Himalayas, these along with the Arunachal Himalayas are conspicuous by the absence of the Shiwalik formations.

6. In place of the Shiwaliks here, the ‘duar formations’ are important, which have also been used for the development of tea gardens.

7. Sikkim and Darjiling Himalayas are also known for their scenic beauty and rich flora and fauna, particularly various types of orchids.

10. Describe the features of The The Arunachal Himalayas

1. These extend from the east of the Bhutan Himalayas up to the Diphu pass in the east.

2. The general direction of the mountain range is from southwest to northeast.

3. Some of the important mountain peaks of the region are Kangtu and Namcha Barwa. 4. These ranges are dissected by fast-flowing rivers from the north to the south, forming deep gorges.

5. Bhramaputra flows through a deep gorge after crossing Namcha Barwa. Some of the

important rivers are the Kameng, the Subansiri, the Dihang, the Dibang and the

Lohit.

11. Describe the features of The The Eastern Hills and Mountains

1.        These are part of the Himalayan mountain system having their general alignment from the north to the south direction.

2.         They are known by different local names. In the north, they are known as Patkai Bum, Naga hills, the Manipur hills and in the south as Mizo or Lushai hills.

3.        These are low hills, inhabited by numerous tribal groups practising Jhum cultivation

4.         Most of these ranges are separated from each other by numerous small rivers.

5. The Barak is an important river in Manipur and Mizoram.

6.The physiography of Manipur is unique by the presence of a large lake known as ‘Loktak’ lake at the centre, surrounded by mountains from all sides.

7. Mizoram which is also known as the ‘Molassis basin’ which is made up of soft unconsolidated deposits.
8. Most of the rivers in Nagaland form the tributary of the Brahmaputra.
9. Two rivers of Mizoram and Manipur are the tributaries of the Barak river,which in turn is the tributary of Meghna;

10. The rivers in the eastern part of Manipur are the tributaries of Chindwin, which in turn is a tributary of the Irrawady of Myanmar.

Work of under ground water

EROSIONAL LANDFORMS BY UNDERGROUND WATER IN KARST TOPOGRAPHY

swallow holes  ; Small to medium sized round to sub-rounded shallow depressions formed on the surface of limestones through solution are  called swallow holes

A sinkhole is an opening more or less circular at the top and funnel-shapped towards the bottom with sizes varying in area from a few sq. m to a hectare and with depth from a less than half a metre to thirty metres or more.

 solution sinks  are  formed  solely through solution action

collapse sinks might start as solution forms first and if the bottom of a sinkhole forms the roof of a void or cave underground, it might collapse leaving a large hole opening into a cave or a void below .it is also known as   DOLINE

 Uvalas

When sink holes and dolines join together because of slumping of materials along their margins or due to roof collapse of caves, long, narrow to wide trenches called valley sinks or Uvalas form.

SOIL FORMATION

SOIL FORMATION

Pedology is soil science.

Pedologist is the one  who studies the soil –

1.Define soil

SOIL is defined as a collection of natural bodies on the earth’s surface containing living matter and supporting or capable of supporting plants.

2. What are the features of soil ?

1. Soil is a dynamic medium in which many chemical, physical and biological activities go on constantly.
2. Soil is a result of decay, it is also the medium for growth.
3. It is a changing and developing body.
4. It has many characteristics that fluctuate with the seasons.
5. It may be alternatively cold and warm or dry and moist.
6. Biological activity is slowed or stopped if the soil becomes too cold or too dry.
7. Organic matter increases when leaves fall or grasses die.
8. The soil chemistry, the amount of organic matter,the soil flora and fauna, the temperature and

                 the moisture, all change with the seasons as well as with more extended periods of time.

.3. What are the soil forming factors? Explain the role of each one of them

Five basic factors control the formation of soils:

(i)                  parent material; (ii) topography; (iii) climate; (iv) biological activity; (v) time.

Parent Material

1.Parent material is a passive control factor in soil formation

2. Parent materials can be any in situ or on-site weathered rock debris (residual soils) or transported deposits

3. Soil formation depends upon the texture(sizes of debris) and structure (disposition of individual grains/particles of debris) as well as the mineral and chemical composition of the rock debris/deposits.

4. Nature and rate of weathering and depth of   weathering mantle are important consideration under parent materials.

5. There may be   differences in soil over similar bedrock and  dissimilar bedrocks may have similar soils above them.

Topography

1. Topography like parent materials is another passive control factor.
2.  The influence of topography is felt through the amount of exposure of a surface covered by parent materials to sunlight and the amount of surface and sub-surface drainage over and  through the parent materials.
3.  Soils will be thin on steep slopes and thick over flat upland areas.

Over gentle slopes where erosion is slow and percolation of water is good, soil formation is very favourable.

Soils over flat areas may develop a thick layer of clay with good accumulation of organic matter giving the soil dark colour.

4. In middle latitudes of northern hemisphere , the south facing slopes exposed to sunlight have different conditions of vegetation and soils and the north facing slopes with cool, moist conditions have some other soils and vegetation.

Climate

Climate is an important active factor in soil formation. The climatic elements involved in soil development are :

 (i) moisture in terms of its intensity, frequency and duration of precipitation - evaporation and humidity;

(ii) temperature in terms of seasonal and diurnal variations.

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

 Eg In climates like wet equatorial rainy areas with high rainfall, not only calcium, sodium, magnesium,

potassium etc. but also a major part of silica is removed from the soil. Removal of silica from the soil is known as desilication. In dry climates, because of high temperature, evaporation exceeds precipitation and hence ground water is brought up to the surface by capillary action and in the process the water evaporates leaving behind salts in the soil. Such salts form into a

crust in the soil known as hardpans.

In tropicalclimates and in areas with intermediate precipitation conditions, calcium carbonate nodules (kanker) are formed.

3  Temperature acts in two ways — increasing or reducing chemical and biological activity.

                                                         Chemical activity is increased in higher temperatures, reduced in cooler temperatures (with an exception of carbonation) and stops in freezing conditions. That is why, tropical soils with higher temperatures show deeper profiles and in the frozen tundra regions soils contain largely mechanically broken materials.

(Q n  Why is the tropical region have deeper soil profiles ? –Ans given above )

Biological Activity

1. The vegetative 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.
2. Dead plants provide humus, the finely divided organic matter of the soil.
3. Some organic acids which form during humification aid in decomposing the minerals of the soil parent materials
4. Intensity of bacterial activity shows up differences between soils of cold and warm climates.
5. Humus accumulates in cold climates as bacterial growth is slow.

 With undecomposed organic matter because of low bacterial activity,layers of peat develop in sub-arctic and tundra climates.

In humid tropical and equatorial climates, bacterial growth and action is intense and dead vegetation is rapidly oxidised leaving very low humus content in the soil. Further, bacteria and other soil organisms take gaseous nitrogen from the air and convert it into a chemical form that can be used by plants. This process is known as nitrogen fixation.

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

6.  The influence of large animals like ants, termites, earthworms, 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.

Time

1.      Time is the third important controlling factor in soil formation.

2.       The length of time the soil forming processes operate, determines maturation of soils and profile development.

3.      A soil becomes mature when all soil-forming processes act for a sufficiently long time developing a profile.

4.       Soils developing from recently deposited alluvium or glacial till are considered young and they exhibit no horizons

or only poorly developed horizons.

5.      No specific length of time in absolute terms can be fixed for soils to develop and mature.

Assignments:

Describe the role of Climate as an important  soil forming factor ?

Describe the role of  life forms in the soil forming  ?

Describe  the role of topography  as an important  soil forming factor ?

Describe the role of Parent rock  as an important  soil forming factor ?