Geology of Dasam Falls in Ranchi district of Jharkhand State, India.

 The Dassam Fall is a natural cascade across the Kanchi River.

by

Dr. Nitish Priyadarshi

Geologist

A waterfall is a place where water flows over a vertical drop in the course of a stream or river. Waterfalls are also called cascades. Waterfalls are commonly formed when a river is young. At these times the channel is often narrow and deep. When the river courses over resistant bedrock, erosion happens slowly, while downstream the erosion occurs more rapidly. As the watercourse increases its velocity at the edge of the waterfall, it plucks material from the riverbed. Whirlpools created in the turbulence as well as sand and stones carried by the watercourse increase the erosion capacity. This causes the waterfall to carve deeper into the bed and to recede upstream. Often over time, the waterfall will recede back to form a canyon or gorge downstream as it recedes upstream, and it will carve deeper into the ridge above it.

The process of erosion, the wearing away of earth, plays an important part in the formation of waterfalls. Waterfalls themselves also contribute to erosion.

Often, waterfalls form as streams flow from soft rock to hard rock. This happens both laterally (as a stream flows across the earth) and vertically (as the stream drops in a waterfall). In both cases, the soft rock erodes, leaving a hard ledge over which the stream falls.

Erosion is just one process that can form waterfalls. A waterfall may form across a fault, or crack in the Earth’s surface. An earthquake, landslide, glacier, or volcano may also disrupt stream beds and help create waterfalls. 

Running water always erodes rock, but some rocks are more resistant than others. So a waterfall occurs when geological forces have produced either a sudden change in rock types or a steepening of a gradient where a stream is flowing. With a break in elevation, a stream or river becomes a waterfall.

The Dassam Falls  (also known as Dassam Ghagh) is a waterfall located near Taimara village in Bundu police station of Ranchi district in the Indian state of Jharkhand. Scenery around the falls is very much beautiful. Tourists visiting the Dasham falls get fascinated after viewing the scenery and glory of the place. Tourists from all over India come to visit this beautiful place, which must form an integral part of your Jharkhand itinerary. Natural beauty of the place attracts visitors throughout the year. Tourists can enjoy bathing in the stream, but they are advised to be cautious while taking a dip in the stream.

Dassam means ten. Since ages and till today, whenever the waterfall is seen, ten streams of water can be seen falling. Hence, the name is given. The Dassam Falls is a natural cascade across the Kanchi River, a tributary of the Subarnarekha River. The water falls from a height of 44 metres (144 ft). The sound of water echoes all around the place. Dassam Falls at one of the edges of the Ranchi plateau is one of the many scarp falls in the region.

The Dassam Falls is an example of a nick point caused by rejuvenation. Knick point, also called a nick point or simply nick, represents breaks in slopes in the longitudinal profile of a river caused by rejuvenation. The break in channel gradient allows water to fall vertically giving rise to a waterfall.

Geology of Chota Nagpur Plateau:

The Chota Nagpur Plateau is a plateau in eastern India, which covers much of Jharkhand state as well as adjacent parts of Odisha, West Bengal, Bihar and Chhattisgarh. The Indo-Gangetic plain lies to the north and east of the plateau, and the basin of the Mahanadi River lies to the south. The Chotanagpur Plateau (22°-25° 30'N and 83°47'-87° 50'E) covering an area of 87,239 sq. km includes Ranchi, Hazaribagh, Singhbhum, Dhanbad, Palamau, Santhal Parganas (Jharkhand) and Purulia dis­tricts (West Bengal). It is composed of Archaean granite and gneiss rocks with patches of Dharwar rocks (phyllite, mica-schists).

The Chota Nagpur Plateau of Jharkhand state is a continental plateau - an extensive area of land thrust above the general land. The plateau has been formed by continental uplift from forces acting deep inside the earth. The Gondwana substrates attest to the plateau's ancient origin. It is part of the Deccan Plate, which broke free from the southern continent during the Cretaceous to embark on a 50-million-year journey that was violently interrupted by the northern Eurasian continent. The northeastern part of the Deccan Plateau, where this ecoregion sits, was the first area of contact with Eurasia.

Chotanagpur consists of a series of plateaus standing at different levels of elevation; the highest general elevation of about 1100 m in the mid-west­ern portion known as the Pat lands. From here the land descends in all directions in a series of steps particularly towards the east until it merges gradu­ally with the Lower Ganga Plain. The sharp break in slope are marked by steep scarps where the rivers like Barakar, Damodar, Subamarekha north and south Koels have carved out deep gorges and water­falls. The most characteristic features of relief are revealed in the Hazaribag and Ranchi plateaus standing at same general elevation (600 m) but separated by the Damodar trough (Permo-Triassic trough fault).

Water falls of Ranchi plateau.

It is the largest part of the Chota Nagpur Plateau. The elevation of the plateau land in this part is about 700 metres (2,300 ft) above mean sea level. The general topography is undulating. The Ranchi plateau gradually slopes down towards south-east into the hilly and undulating region of Singhbhum (earlier Singhbhum district or what is now Kolhan division. The plateau is highly dissected. Damodar River originates here and flows through a rift valley. To the north it is separated from the Hazaribagh plateau by the Damodar trough.To the west is a group of plateaux called pat.

There are many waterfalls at the edges of Ranchi plateau where rivers coming from over the plateau surface form waterfalls when they descend through the precipitous escarpments of the plateau and enter the area of significantly lower height. The North Karo River has formed a 17 metres (56 ft) high Pheruaghaugh Falls at the southern margin of Ranchi plateau. Such falls are called scarp falls. Hundru Falls (75 m) on Subarnarekha River near Ranchi, Dassam Falls (44 m) on Kanchi River, east of Ranchi, Sadni Falls (60 m) on Sankh River (Ranchi plateau) are examples of scarp falls. Sometimes waterfalls of various dimensions are formed when tributary streams join the master stream from great height forming hanging valleys. At Rajrappa (10 m), the Bhera river coming over from the Ranchi plateau hangs above the Damodar River at its point of confluence with the latter. The Jonha Falls (25.9 m) is another example of this category of falls. In fact the Gunga River hangs over its master stream, Raru River (to the east of Ranchi city) and forms the said falls.

Formation of Waterfalls in Ranchi Plateau.

The waterfalls of Ranchi plateau including Dasam falls are due to disturbances in late geological age. The Ranchi plateau (or the whole of Peninsular India) believed to have undergone uplift as the side effects of the Himalayan orogeny particularly during the late Tertiary. As the streams descend they are marked by waterfalls.

The Chotanagpur Plateau is made up mainly of Precambrian rocks but has witnessed uplifts synchronously with Himalayan uplift in the Cenozoic.

Some times, waterfalls of varying dimensions are formed when the tributary streams join their master streams from great height forming hanging valleys. In other words, hanging valley falls are formed when the level of the junction of the tributary streams is much higher than the level of the main valley of the master stream. The Rajrappa falls ( 10 m.) at the junction of the Bhera river and the receiving Damodar river (located to the north of Ranchi city) is a typical example of hanging valley waterfalls as the Bhera river after coming from over the Ranchi Plateau hangs above the Damodar river as its confluence with the latter. The Gautamdhara or Johna falls ( 25.9 m.) is another example of this category of falls. In fact, the Gunga river hangs above its master stream, Raru river, ( to the east of Ranchi city) and forms the said falls.

Some falls of Ranchi plateau comes under knick point falls. The breaks in channel gradient caused by rejuvenation are called knick points or heads of rejuvenation. These breaks in channel gradient or knick points denote sudden drops of elevation in the longitudinal profile of the rivers and allow the water to fall down vertically giving birth to waterfalls of varying dimensions. Hundru falls ( 76.67 m) on Subarnarekha river ( near Ranchi city), Johna or Gautamdhara falls at the confluence of Raru and Gunga rivers (to the east of Ranchi). Dasam falls ( 39.62 m and 15. 24 m ) on Kanchi river (east of Ranchi) are the examples of knickpoint falls.

Geology of Dasam falls:

 

Surface rocks surrounding the area are highly smooth. This is due to abrasion. Abrasion is the mechanical scraping of a rock surface by friction between rocks and moving particles during their transport by wind, glacier, waves, gravity, running water or erosion. This phenomenon is active there from millions of years.

Ptygmatic folding of quartzo-feldspathic veins are prominent on the Precambrian (granite-gneiss) rocks of the area.

The ptygmatic folding term is now used essentially for highly contorted quartzo-feldspathic veins found in areas of intense metamorphism and granitisation. Their origin has been a matter of controversy, two different theories have been put forward 1.the veins were originally intruded as flat sheets and the folding is due to deformation of the host rock. 2. Folding took place during the process of injection, which occurred under special circumstances.

It is possible to demonstrate experimentally that material being injected into a weaker host material will develop ptygmatic folding, if it encounters a more rigid mass. This is clearly what happens when ptygmatic veins are formed in granitised or migmatic materials.

 Fig. Ptygmatic folding in rocks of Dasam falls.

Fig. Quartzo-feldspathic intrusion.

Fig. Faulting in the rocks of Dasam Falls.

There are also many potholes in the rocks of  Dasam falls area. Potholes are the kettle-like depressions in the rocky bed of streams. The stream beds in Ranchi plateau are frequently dotted with potholes. Potholes are due to localized drilling action of rock fragments. Where there is an originally minor depression the water of the stream will undergo swirling and the dancing rock fragments will grind against the side and bottom of the depression which will undergo gradual enlargement in perimeter and depth.

  Fig. Potholes in the rocks of Dasam Falls.

Potholes develop particularly in coarse-grained rocks like sandstone or weathered granite

( as in Dasam Falls). In recently uplifted areas like Dasam falls the supply of the boulders or angular rock fragments encourages potholing. The original minor depression could result from local lithological weakness of the rock or joint intersection or the erosion of a local rock piece. The hollow begins to arrest rock fragments.

  

Reference:

Ahmad, E. 1985. Geomorphology. Kalyani Publishers, New Delhi.

Mahadevan, T.M. 2002. Geology of Bihar and Jharkhand. Geological Society of India, Bangalore.

Singh, S. 1994. Physical Geography. Prayag Pustak Bhawan, Allahabad, India.

Subarnarekha river in Jharkhand State of India is drying up.

Origin source is under threat.by
Dr. Nitish Priyadarshi

Fig.1 In year 2009 the origin source was emitting full of water. Fig.2. In year 2011 source is completely dried.
Fig.3. In year 2009 area near the source well was filled with water and vegetation.

Fig.4. In year 2011, only small rivulet is left. Green vegetation has vanished.
Few days ago I with my three friends decided to visit the origin place of the famous Subarnarekha (Swarnrekha) River of Jharkhand State in India. This was my third visit. My friends were more curious to see how Subarnarekha originates from the place. This place is 30 kms form the Ranchi city, the capital of Jharkhand State. My friends were imagining that area must be full of greeneries and water. As we were approaching the area our excitement was mounting up. Our car stopped few hundred meters before the spot. We came out of the car and looked around in the clean atmosphere. But what we saw was only dry soils and rocks with very less surface water which was also contaminated with iron. Iron contamination was seen the form of thin oil film on the surface water. Source of iron to the water is from the laterite rocks of that area. Laterite rocks contain high amount of iron which is visible in the form of red colors of the rocks.

My friends were more depressed to see the area as it was just opposite to their imagination. No green luster, no water only desert. Two years ago when I visited the area, different origin spots were emitting clean water and vast area was under flowing water. Today except one or two spots all were dried up.

From last two years Jharkhand is not receiving sufficient rainfall which has adversely affected the river flow and its source. The rain water percolates downwards to recharge the groundwater in the catchment areas of Subarnarekha river. Due to lack of rain water the area has gone dry affecting the flow.

The basin of the Subarnarekha is smaller amongst the mutli-state river basins in India. The rain-fed river covers a drainage area of 1.93 million hectares.

After originating near Piska/ Nagri, near Ranchi, the capital of Jharkhand, the Subarnarekha traverses a long distance through Ranchi, Seraikela, Kharsawan and East Singhbhum districts in the state. Thereafter it flows for shorter distances through Paschim Medinipur district in West Bengal for 83 kilometres (52 mi) and Balasore district of Orissa. There it flows for 79 kilometres and joins the Bay of Bengal near Talsari. The total length of the river is 470 kilometres.

The name Subarnarekha means “the thread of gold” and the sands of the river and some of its tributaries are auriferous, but without any prospect.

The largest river in Jharkhand, the Subarnarekha flows eastward upto Muri, galloping down the Hirni, Dasam, Johna and Hundru falls. It then takes a sharp turn to the south and flows into the gap between the Ajodya (Bhagmundi) hills on the east and the Ranchi uplands in the west.

The prominent tributaries of the Subarnarekha are Kharkai, Raru, Kanchi, Damra, Karru, Chinguru, Karakari, Gurma, Garra, Singaduba, Kodia, Dulunga and Khaijori.The Kharkai meets the Subarnarekha at Sonari(Domuhani), a neighbourhood of Jamshedpur.


If this river really goes dry it is not only going to affect the different falls but also two big dams Hatia and Rukka. These two dams are used to quench the thirst of half of the population of Ranchi district. These two dams are already under threat of depleting water level.

The declining water levels in major rivers of Jharkhand State much ahead of the dry season is lowering the underground water levels and also affecting cultivation in State. Environmentalists fear negative changes in overall climate will make the region more prone to calamities.

The adverse impacts of global climate changes (CC) have forced the Subarnarekha River to dry up abnormally much ahead of the dry season now like every year in recent times.
Reduced run-off is increasing the pressure on freshwater resources in much of the state, especially with more demand for water as population increases. Freshwater being a vital resource, the downward trends are a great concern.

Dasam falls a tragic picnic spot in Jharkhand State of India. Rocks structure plays major role.

Geological factors may be responsible for such accidents.

Potholes present in the rocks are dangerous.

by

Dr. Nitish Priyadarshi

Waterfalls offer breathtaking views and are cool places to relax and feel the astounding beauty and benefits of nature. But in some cases, these wonderful gifts of nature to mankind bring tragedy to people.

A fun filled day out at the famous Dasam falls, near Ranchi city, proved fatal for four youngsters. They drowned while enjoying a picnic on Saturday (20th March).

This is not the new case. Every year many people die in this fall especially from November to March. Causes of deaths were due to drowning.

The Dasam (meaning ten) falls also known as Dasomghagh, 40 Kms south-east of Ranchi city near Taimara valley is formed by the Kanchi river falling over a ledge of a rock in a sheer descent of 114 feet amid rocky and sylvan scenery.

There are different mythological stories behind such accidental deaths. But no scientific investigations have been done to know the exact cause of sudden drowning.

I have tried to point out some geological factors which may be responsible for such accidents.

In spite of great falls like Hundru and Jonha deaths occurs only in Dasam falls. Geological cause behind this is the rock structures. Surface rocks surrounding the area are highly smooth. This is due to abrasion. Abrasion is the mechanical scraping of a rock surface by friction between rocks and moving particles during their transport by wind, glacier, waves, gravity, running water or erosion. This phenomenon is active there from millions of years. People wearing leather shoes or slippers are more prone to accident on this polished surface. There are more chances for the people of getting slipped inside the water and injuring their heads.

Other major factor responsible for such accidents is the presence of pot holes. Many pot holes are found in the river beds in Jharkhand state. Jharkhand rocks favor such formations. Some are such large that even the elephants can also be trapped especially in the Palamau area.

Potholes are usually regarded as one of the erosional features. The traditional interpretation is in terms of the process of abrasion of the bedrock by rotary currents inside the potholes, and vibration of pebbles and stones by the water, that gradually wore the holes deeper and deeper into the bedrock.

In the usual interpretation, potholes are considered to be the effects of erosion by streams and rivers over very long periods of time. The actual work of abrasion is considered to have been done either by hard grains of sand held in suspension by the rapidly flowing water; or by large boulders, called "grinders," in the bottom of the pothole, that were agitated constantly by the currents swirling around inside.

Strong under currents is generated when water enters such pot holes. These currents act as suction pump. When people enter in water there are more chances to get trapped and pulled inside. State government must flag such dangerous potholes in Dasam falls and people must be warned of such areas.

Even the crevices or the long gaps present in the rocks beneath the water are dangerous. People entering the water are unaware of such crevices or gaps between the rocks. They are the silent killers. Rocks around such falls in Ranchi district are filled with crevices and depressions.

As Dasam falls is flooded with people during the season, it is more prone to such accidents. Rocks beneath the water and surrounding play a major role to make this spot picturesque. But they also act as killer stone.