Tuesday, July 29, 2008

Topography

Topography

The Great Escarpment



Hanuman & Shiva Shrines at Kundaibari Pass - the Western Ghats begin here.

The Western Ghats form an almost unbroken rampart on the fringe of western peninsula parallel to the west coast for about 1600 km and often hardly 40 km from the Arabian Sea.

They start immediately south of the Tapti river, the northern most point being the Kundaibari pass (21006���N, 74011���E) near Brahmavel in Dhule district of Maharashtra ending near Kanya-kumari (80���N) barely 20 km from the sea in Tamil Nadu. They cover an area of approximately 1,59,000 sq. km with an average elevation of 900-1500 m. ASL, obstructing the monsoon winds from the south west and the orographic effect is considerable. Although the average heights of the Ghats is less than1500 m. ASL, in the southern reaches it rises 2000 m and to exceptionally higher peaks of 2,500 m and above.
Along its entire length, the Western Ghats range has only one total discontinuity, the Palghat Gap in Kerala where for more than 30 km there is a gap which has a floor height of less than 100 m ASL. This discontinuity is perhaps of tectonic origin through which a river may have flowed in ancient times. The peninsular plateau is highest in the south and west and slopes eastward, the eastern edge forming the broken up Eastern Ghats. The Eastern and the Western Ghats meet along the Moyar Gorge with the Billigirirangana Hills along the north-eastern side and the the Nilgiris in the south-west.
Based on the topography and geology, the Western Ghat region is divided into three distinct subregions:

Northern Western Ghats (Tapti river to Goa)

This region consists of the most homogeneous part of the Western Ghats, hugging the coast for almost 600 km. It corresponds to the western edge of the vast plateau formed by massive horizontal outflow of volcanic lava which cooled to form dark grey basalt.
The layer of lava often interlaced with non-volcanic debris - View from Arthur���s Seat, Mahabaleshwar

The scarp of the Ghats in this region presents a magnificent profile of over 1,000 m of successive volcanic layers, which on erosion have produced a typical trappean landscape, forming a formidable well-dissected wall looking over the narrow west coast plains, buton the eastern side descending in steps one below the other. It is in this region that the full significance of the term ���ghats��� (steps of a stair-case) becomes clear. The layers of lava are quite often interlaced with non-volcanic debris. Sometimes these form intertrappean deposits holding plant and animal fossils. The elevation is generally between 700 and 1,000 m, but some of the pinnacles attain greater heights; the tallest are the Kalsubai (1,646 m) near Igatpuri, Salher (1,567 m) 90 km north of Nasik and the famous Mahabaleshwar (1,438 m).

Mangi & Tungi - The Twin Peaks in the Selbari Range

The escarpment is not a simple erosional feature; some geologists believe that it marks the location of a broad zone of en echelon deep-seated faults. Landsat imagery shows a large density of faults striking NW-SW along the trend of this escarpment roughly parallel to the coast, in which 33 hot springs have been noted and which have been interpreted as indicative of a fault.

Terraced flanks - the ���Ghats or steps���, Maharashtra

The coastal zone here called Konkan, is a narrow strip about 50-60 km wide. It is made up of a series of more or less high hills, some of them like Matheran (700 m) almost reaching the height of the plateau and bears testimony of regressive erosion.

Central Western Ghats (Goa to Nilgiris)
The basaltic outpourings cease to the north of Goa. The Middle Western Ghats run from a little south of 160N latitude up to Nilgiri Hills. Towards the south, the Ghats consist of complex formation of pre-cambrian rocks. In the central Western Ghats, the rocks are predominantly of Dharwar system (among the oldest in India) and Peninsular gneisses.
The Western scarp is considerably dissected by headward erosion of the west flowing streams. The elevation generally range between 600 to 1000 m up to 13030���N. The Ghats lose their graded appearance and form a steep barrier whose height becomes more irregular. They rise suddenly at Kodachadri (1343 m)and fall to about 600 m at Agumbe.
The ���Iron mountains���- Kudremukh range

From Kudremukh (1,892 m) up to Palghat Gap, the edge of the plateau is very often higher than 1,000 m. and the peaks become more numerous and higher - Pushpagiri (1,713 m) in the North Kodagu, Tadianamol Betta (1,745 m), Banasuram (2,060 m), Vavul Mala (2,339 m) at the edge of the Wayanad plateau.

Towards 11030���N, the Western Ghats composed of hard Charnokites, rise abruptly in the Nilgiri horst where they join the Eastern Ghats. The Nilgiri mountains constitute an elevated plateau dominated by two of its highest peaks, the Dodabetta (2,637 m) and Makurti (2,554 m) overlooking Palghat Gap from a height of more than 2,000 m.

On the Mysore plateau, whose average elevation range from 700 to 900 m we find reliefs formed by tectonic events such as spectacular horseshoe of the Bababudan hills which extends from Hebbe through Kemmanagundi and Attigudi to Mulainagiri (1,923 m) which is the highest peak in Karnataka.
Brahmagiris near Iruppu, Kodagu

The other tallest peak is Bababudangiri (Chandradrona Parvata 1,894 m). The width of the coastal zone is also more variable here than in Maharashtra. It is about 40 km wide at the latitude of Goa and then suddenly narrows near Karwar where the Ghats dip into the sea with peaks emerging as picturesque islands.
The Ghats dip into the sea near Karwar

This advance of the relief is carved by deep valleys of the Kalinadi, Gangavali and Sharavathy. The last drops from a height of 250 m creating the famous Jog falls.
To the south of 140 N, the coastal zone now called South Kanara, widens once more to about 80 km. The coastal region after Kodagu known as Malabar is not more than 30 km wide up to the latitude of Kozikode. From here it widens out to about 60 km till the Palghat Gap. The coastal hills in the entire region, particularly to the north of Mangalore are mostly tabular relief hardened by iron oxides. These reliefs are practically bare and present a characteristic landscape.


Charmadi Ghats, Karnataka
Southern Western Ghats (South of the Palghat Gap)

The Western Ghats are separated from the main Sahyadri Range by the Palghat Gap which is about 30 km wide and they appear abruptly as the Anaimalai-Palni block whose high plateau attain a height of 2,695 m in the Anaimudi peak, the highest point in south India. The Nelliampathis

This block is a composite range ismade up of the Nelliampathy plateau (drained by Chalakudi) to the west, the Anaimalai plateau (largely converted into tea plantations and distinctly elevated to the east) in the centre and the Palni horst overlooking the peneplain of Tamil Nadu from a height of almost 2,000 m.
Anaimudi - the highest peak in the south 2,695 m(8,843 ft). Bill Aitken called it ���Black Moby Dick��� - the Great Whale

To the south of this west-east oriented block, the Ghats display further changes. Here they form an elevated plateau slanting towards the west - the Periyar plateau, thus named after its most important river. The eastern part of this plateau forms Elamalai range, better known as Cardamom Hills because of its plantations. This central range attains its peak at Devar Malai (1,922 m) and terminates in the east by sheer cliff 1,000 m high. From this, the SW-NE oriented Varushanad massif is detached and continued by the Andipathi, which together with Palni hills embraces the Kambam Valley.

South of Devar Malai, at about 90N, the Ghats are once again interrupted by narrow Shencottah Pass (alt. 160 m). From here they continue as a narrow ridge with steep slopes to the west as well as to the east, until about 20 km before Kanyakumari. This last bit is very rugged and its highest peak is the Agasthyamalai (1,869 m). Three regions may be distinguished here; Agasthyamalai proper, Mahendragiri to the south and the Tirunelveli hills on the eastern slopes. The coastal zone (30-50 km wide) constituting Travancore is made up of convex shape hills with rounded summits. Here we do not find the tabular reliefs of South Kanara and Konkan since their formation at this latitude is probably more difficult due to short, dry season.

The vegetation types are characterised by low level tropical evergreens turn to Shola grasslands on the cool wind swept slopes of the higher ranges. Primary or secondary moist deciduous forests cover the lower western hills. Moist deciduous forests are also common on the eastern slopes in the rain shadow area. Dry deciduous and even scrub vegetation characterises the eastern slopes where the humidity is low and the winds are high.


The Imperial Gazetteer of India - 1907 gives a very vivid description of the region which is reproduced below:


Western Ghats - a range of mountains about 1,000 miles(1,600 km) in length, forming the western boundary of the Deccan and the watershed between rivers of peninsular India. The Sanskrit name is ���Sahyadri���.

The range, which will be treated here with reference to its course through Bombay, Mysore and Coorg and Madras, may be said to begin at the Kundaibari pass in the south western corner of the Khandesh district of Bombay Presidency, though the hills that run eastward from the pass to Chimtana and overlook the lower Tapti valley, belong to the same system. From Kundaibari (21006���N, 740 11���E) the chain runs southward with an average elevation which seldom exceeds 4,000 ft., in a line roughly parallel with the coast, from which its distance varies from 20 to 65 miles. For about 100 miles up to a point near Trimbak, its direction is somewhat west of south; and it is flanked on the west by the thickly wooded and unhealthy tableland of Peint, Mokhada and Jawhar (1500 ft) which forms a steep barrier between the Konkan lowlands and the plateau of the Deccan (about 2000 ft). South of Trimbak the scarp of the western face is more abrupt; and for 40 miles, as far as the Malsej pass, the trend is south-by-east changing to south-by-west from Malsej to Khandala and Vagjai (60 miles), and again to south by east from here until the chain passes out of the Bombay Presidency into Mysore near Gersoppa ( 14010���N, 74050���E).

On the eastern side the Ghats throw out many spurs or lateral ranges that run from west to east, and divide from one another the valleys of the Godavari, Bhima and Kistna river systems. The chief of these cross ranges are Satmalas, between the Tapti and Godavari valleys; the two ranges that break off from the main chain near Harishchandragarh and run south eastwards into the Nizam���s Dominions, enclosing the triangular plateau on which Ahamad-nagar stands, and which is the watershed between the Godavari and the Bhima; and the Mahadeo range, that runs eastward and southward from Kamalgarh and passes into the barren uplands of Atpadi and Jath, forming the watershed between the Bhima and the Kistna systems. North of the latitude of Goa the Bombay part of therange consists of Eocene trap and basalt, often capped with laterite, while farther south are found such older rocks as gneiss and transitional sandstones.
The flat-topped hills, often crowned with bare wall like masses of basalt, or laterite are clothed on their lower slopes with jungles of teak and bamboo in the north; with jambul (eugenia jambolana), ain (Terminalia tomentosa) and nana (Lagerstroemia parviflora) in the centre; and with teak, blackwood, and bamboo in the south.
On the main range and its spurs stand a hundred forts, many of which are famous in Maratha history. From north to south, the most notable points in the range are the Kundaibari pass a very ancient trade route between Broach and the Deccan; the twin forts of Salher and Mulher guarding the Babhulna pass; Trimbak at the source of holy river Godavari; the Thal pass by which the Bombay-Agra road and the northern branch of the Great Indian Peninsula Railway ascends the Ghats; the Pimpri pass, a very old trade route south between Nasik and Kalyan or Sopara, guarded by the twin forts of Alang and Kulang; Kalsubai (5427 ft), the highest peak in the range; Harishchandragarh (4691 ft); the Nana pass, a very old route between Junnar and Konkan; Shivner, the fort of Junnar; Bhimashankar, at the source of the Bhima; Chakan, an old Musalman stronghold; the Bhor or Khandala pass, by which the Bombay-Poona road and the southern branch of the Great Indian Peninsula Railway enters the Deccan, and on or near which are the caves of Kondane, Karli, Bhadja and Bedsa; the caves of Nasdur and Karsambla below the forts of Sinhagarh and Purandhar in the spurs south of Poona; the forts of Raigarh in the Konkan and of Pratapgarh between the new Fitzgerald ghat road and the old Par pass; the hill station of Mahabaleshwar (4717 ft) at the source of the Kistna; the fort and town of Satara; the Kumbharli pass leading to the old towns of Patan and Karad; the Amba pass, through which runs the road from Ratnagiri to Kolhapur; the forts of Vishalgarh and Panhala; the Phonda pass, through which runs the road from Deogarh to Nipani; the Amboli and the Ram pass, through which run two made roads from Vengurla to Belgaum; Castle Rock, below which passes the Railway from Marmagao to Dharwar; The Arabail pass on the road from Karwar to Dharwar; the Devimane pass on the road from Kumta to Hubli, and the Gersoppa Falls on the river Sharavati.

On leaving the Bombay Presidency, the Western Ghats bound the State of Mysore on the west, separating it from the Madras district of South Kanara, and run from Chandragutti (2,794 ft) in the north-west to Pushpagiri on the Subramanya hill (5,626 ft) in the north Coorg and continue through Coorg into Madras.

In the west of the Sagar taluk, from Govardhangiri to Devakonda, they approach within ten miles of the coast. From there they trend south-eastwards, culminating in Kudremukh (6,215 ft) in the southwest of Kadur district, which marks the watershed between Kistna and Cauvery systems. They then bend east and south to Coorg, receding to 45 miles from the sea. Here to numerous chains and groups of lofty hills branch off from the Ghats eastwards, forming the complex series of mountain heights south of Nagar in the west of Kadur district. Gneiss and hornblende schists are the prevailing rocks in this section, capped in many places by laterite, with some bosses of granite. The summits of the hills are mostly bare, but the sides are clothed with magnificent evergreen forests. Ghat roads to the coast have been made through the following passes: Gersoppa, Kollur, Hosangadi, and Agumbe in Shimoga district; Bundh in Kadur district, Manjarabad and Bisale in Hassan district.

In the Madras Presidency, the Western Ghats continue in the same general direction, running southwards at a distance of from 50 to 100 miles from the sea until they terminate at Cape Comorin, the southern most extremity of India. Soon after emerging from Coorg they are joined by the range of the Eastern Ghats, which sweeps down from the other side of the peninsula; and at the point of junction they rise up into the high plateau of the Nilgiris, on which stand the hill stations of Ootacamund (7,000 ft), the summer capital of the Madras Government, Coonoor, Wellington, and Kotagiri and whose loftiest peaks are Dodabetta (8,760 ft) and Makurti (over 8,000 ft).
Immediately south of this plateau the range, which now runs between the districts of Malabar and Coimbatore, is interrupted by the remarkable Palghat Gap, the only break in the whole of its length. This is about 16 miles wide, and is scarcely more than 1,000 ft above the level of the sea. The Madras Railway runs through it, and it thus forms the chief line of communication between the two sides of this part of the peninsula.


South of this gap the Ghats rise abruptly again to even more than their former height. At this point they are known by the local name Anaimalais, or ���elephant hills���, and the minor ranges they here throw off to the west and east are called respectively the Nelliam-pathis and the Palni Hills. On the latter is situated the sanatorium of Kodaikanal. Thereafter, as they run down to Cape Comorin between the Madras Presidency and the native state of Travancore, they resume their former name.

North of the Nilgiri plateau the eastern flank of the range merges somewhat gradually into the high plateau of Mysore but its western slopes rise suddenly and boldly from the low coast south of the Palghat Gap both the eastern and western slopes are steep and rugged . The range here consists throughout of gneisses of various kinds, flanked in Malabar by picturesque terraces of laterite which shelve gradually down towards the coast. In elevation it varies from 3,000 to 8,000 ft above the sea, and the Anaimudi peak (8,839 ft) in Travancore is the highest point in the range and in southern India. The scenery of the Western Ghats is always picturesque and frequently magnificent, the heavy evergreen forest with which the slopes are often covered aiding greatly to their beauty. Large games of all sorts abounds, from elephants, bisons and tigers to the Nilgiri ibex, which is found nowhere else in India.

Before the days of roads and railways the Ghats rendered communication between the west and east coasts of the Madras Presidency a matter of great difficulty; and the result has been that the people of the strip land which lies between them and the sea differ widely in appearance, language, customs, and laws of inheritance from those in the eastern part of the Presidency. On the range itself, moreover, are found several primitive tribes, among whom may be mentioned the well known Todas of the Nilgiris, the Kurumbas of the same plateau, and the Kadars of Anaimalais. Communications across this part of the range have, however, been greatly improved of late years. Besides the Madras Railway already referred to, the line from Tinnevelly to Quilon now links up the two opposite shores of the peninsula, and the range is also traversed by numerous ghat roads. The most important of these latter are the Charmadi ghat from Mangalore in South Kanara to Mudgiri in Mysore; The Sampaji ghat between Mangalore and Mercara, the capital of Coorg; the roads from Cannanore and Tellichery, which lead to the Mysore plateau through the Perumbadi and Peria passes; and the two routes from Calicut to the Niligiri plateau up the Karkur and Vayittiri-Gudalur ghats.

NOTABLE PEAKS IN THE WESTERN GHATS

Name of the peak & location Height(m) (ft)

1. Anaimudi 2,695 (m) 8,839(ft) Anaimalai Hills, Kerala
2. Dodabetta 2,637 (m) 8,649 (ft) Nilgiri Hills, Tamil Nadu
3. Makurti 2,554 (m) 8,377 (ft) Nilgiri Hills, Tamil Nadu
4. Vembadi Shola 2,506 (m) 8,220 (ft) Kodaikanal Hills, Tamil Nadu
5. Vahul Mala (Camel���s Hump) 2,339 (m) 7,672 (ft) Southern Sahyadris, Kerala
6. Banasuram 2,060 (m) 6,757 (ft) Southern Sahyadris, Kerala
7. Kottai Malai 2,019 (m) 6,622 (ft) Varushanad Hills, Keral-Tamil Nadu
8. Mulainagiri 1,923 (m) 6,307 (ft) Bababudan Hills, Karnataka 9. Devar Malai 1,922 (m) 6,304 (ft) Kerala
10. Badabudangir (Chandradrona Parvata) 1,894 (m) 6,212 (ft) Karnataka
11. Kudremukh 1,892 (m) 6,206 (ft) Central Sahyadris, Karnataka
12. Agasthyamalai 1,869 (m) 6,130 (ft) Kerala-Tamil Nadu
13. Tadianamol Betta 1,745 (m) 5,724 (ft) Kodagu, Karnataka
14. Pushpagiri 1,713 (m) 5,619 (ft) Kodagu, Karnataka
15. Mahendra Giri 1,654 (m) 5,425 (ft) Kerala-Tamil Nadu
16. Kalsubai 1,646 (m) 5,399 (ft) Northern Sahyadris, Maharashtra
17. Salher 1,567 (m) 5,140 (ft) Northern Sahyadris, Maharashtra
18. Ballalrayan Durga 1,504 (m) 4,933 (ft) Central Sahyadris, Karnataka 19. Gopalaswamy Betta 1,454 (m) 4,769 (ft) Karnataka - Tamil Nadu
20. Pratapgad 1,438 (m) 4,717 (ft) Central Sahyadris, Maharashtra
21. Kodachadri 1,343 (m) 4,405 (ft) Karnataka
22. Andipatti Hills 1,301 (m) 4,267 (ft)Tamil Nadu
23. Sadura Giri 1,271 (m) 4,169 (ft) Varushanad Hills, Tamil Nadu

2 comments:

Unknown said...

Beautiful article, with lots of useful information. A good map featuring these place names will also help. It has spurs of information that can be developed on various topics you have touched upon...thank you

Gyaan Deep said...

very good article on western ghat it covers almost all important inforations related to western ghat. thanks for sharing