Danger in the hills of Ranchi district in Jharkhand State of India.

 

Hills are becoming vulnerable to major land slides in future.

by 

Dr. Nitish Priyadarshi

Geologist and Assistant Professor,

Department of Geology,

Ranchi University,

India.

Below are the photographs of the hills around Ranchi the capital city of Jharkhand state of India. During my recent visit to these hills  in Patratu valley and Angada block  I saw some of the areas which are vulnerable to major land slides in coming future. 

 

 

 

Most of the hills are highly weathered. They are steep-sided residual hills made of massive granite-gneiss. Few hills especially in Angada block and Patratu valley near Ranchi are showing the trend of landslides. Many slopes are already in delicate equilibrium and slight increase in rainfall and human interference may trigger the land slides under the influence of gravity. The flow of the Nalkari river, the tributary of Damodar river, can get blocked due to possible land slide in the Patratu valley . Nalkari river contributes water to the Patratu Dam. Excessive precipitation are the frequent cause for landslides which weakens the slope materials. Other factors that weaken slope materials also contribute to the occurrence of landslides. Ranchi receives 1200 to 1600 mm annual rainfall.  Most of the hills are having steeper slopes so they are more exposed to rapid erosion than the gentler ones.   Many hills of the Ranchi plateau are highly susceptible to slope instability due to the immature and rugged topography, fragile rock conditions, and high rainfall.

The Ranchi Plateau, composed mostly of gneisses and granites, is about 2000 ft. above sea level. The topography is roughly undulating with terraced slopes ending on the one hand on the banks of a local stream and on the other in local upland which may or may not have a low hill, or which may or may not consist of solid rocks exposed bare soils.

The present topographic features of Chotanagpur  ( Ranchi plateau) are a clue to the past and geologists think that before the Himalayan movement started in Tertiary times Chotanagpur and adjoining areas were a low peneplain. As a side-effects of the violent Himalayan movements, parts of peninsular upland in general and Chotanagpur peneplain in particular began to be successively uplifted. The Himalayan movements occurred three times during Early and Late Tertiary and Pleistocene times and probably the Chotanagpur peneplain was also concurrently subjected to three successive uplifts.  

Landslides occur when the slope (or a portion of it) undergoes some processes that change its condition from stable to unstable. This is essentially due to a decrease in the shear strength of the slope material, to an increase in the shear stress borne by the material, or to a combination of the two. A change in the stability of a slope can be caused by a number of factors, acting together or alone.

Landslides can be initiated in slopes already on the verge of movement by rainfall, snowmelt, changes in water level, stream erosion, changes in ground water, earthquakes, volcanic activity, disturbance by human activities, or any combination of these factors.

Causes of landslides in Ranchi plateau include:

1.     Saturation by rain water infiltration.

2.     Increase of pore water pressure by rain water infiltration.

3.     Increase of hydrostatic pressure in cracks and fractures.

4.     Physical and chemical weathering.

5.     Deforestation, cultivation and construction.

6.     Blasting and mining.

7.     Erosion by river flows.

Ruins of an ancient structure found near Ranchi in Jharkhand state of India.

Is it Geological weathering or remains of ancient structure?

by

Dr. Nitish Priyadarshi

We live in a highly advanced, technical world, but there are nevertheless a great many mysteries all around us. Ancient places and mysterious beings, sunken worlds and cultures, landscapes imbued with symbolism, unexplained apparitions, and unbelievable finds from ancient times- all of these remain mysteries for human kind, despite intense investigation. Legendary ancient places tell stories that provide archaeologists and historians with information that is essential for the study of culture.

In the past, we have often been less than careful with old buildings and religious sites, many of which were left to fall to pieces after their abandonment. Lack of repair and natural forces take care of the rest, leaving the large part of most ancient sites in ruins. These ruins can still give us a lot of information about the production, form, and quality of building materials. They can also tell us what led to their destruction. The location and function of the structures can be used to help interpret past cults and cultures. Sometimes problem does arise to interpret such structures as some of it very much resembles with typical geological structures or weathering.

We have to be very careful in studying such structures or rocks. This report unreels the unsolved mysterious rock structures and cuttings, on the hills some 25 km north of Ranchi city, capital of Jharkhand State of India. These structures have recently been exposed due to expansion of road construction, and now are being continuously destroyed due to on going construction.

Ranchi possesses remnants of numerous pre-historic stone implements. Its monuments, some of which are credited to the Asuras by the Mundas, yielded such a mixed assortment of finds as polished stone stools, Carnelian beads, wheel-made pottery, copper and bronze objects, copper and gold ornaments and even iron slags, that it is impossible to date them to any one age.

Credit goes to my senior friend Mrs. Elizabeth Borde who told me about these mysterious unsolved rock structures. She used to visit that area from her childhood. When I visited the area with her, I was surprised to see that some weathered structures which very much resemble to ancient rock pillars were lying at the road side. Many were still found intact with rocks of that area.

The way the rocks are carved, it clearly indicates that people at that time in this area were perfect in making such structure. The rock cuttings and stone blocks fitting snugly together were probably hewed from granite rocks.

At first instance it very much resembled with that of typical geological weathering or different layered rocks. As a geologist I looked on the structures that showed a typical pattern of weathering which are not common in other parts of these state. Though it was a weathering but not of usual local hard rocks but that resembling to some ancient structures like stratified pillars.

I was also surprised to see some geometrical lines and angles, rock cuttings and even plant imprints and radiating lines on the rock surface.

Ranchi rocks are mainly Chotanagpur Granite gneiss with Quartzite, Amphibolites etc. Chotanagpur Granite Gneiss forms the country rock of the district and is a part of the enormous intrusive mass. It shows wide variations from fine to coarse grained and porphyritic types, and form massive to highly gneissic types. Weathered structures seen here are not common in Granitic rocks.

Geologists may feel that structures are the outcome of natural weathering, but the pattern of weathering is peculiar. It seems that in ancient days there must have been huge structure, may be of Buddhism, build up on the top of the hills, which finally collapsed either due to natural disaster or some invasions.

Some scholars feel that Buddhism influenced this area in Early History. There are several ruins of the Buddhist monuments and statutes in different places of Jharkhand. Apart from Buddhism, Jainism also makes its presence in Jharkhand.

In early history this inaccessible region full of dense forest and treacherous terrain coupled with its wild inhabitants, appears never to have been completely subdued. It is said that the “Atavi” (or forest states) too acknowledged the supremacy of Magadh during the reign of Maurayas.

Road construction is going on putting threat on these mysterious rock structures. Early destruction took place in 1960 when rocks of these structures were used for constructing wall guard along the road side. Even today villagers used these rocks for constructing their houses. The ruins of these pillars, rock cuttings may be vital clue to ancient civilizations developed and gradually vanished from this area. More research is needed to reveal the age and the mystery of the structures and rock carvings.

Rare earths elements are in increasingly short supply as world demand surges.

Jharkhand State of India can play major role in Rare Earth Elements production.

by

Dr. Nitish Priyadarshi

China has been steadily reducing export quotas since 2005 for rare earth elements, which consist of 17 metals used in crucial new green technologies like hybrid cars, wind turbines and superconductors, as well as in missile guidance systems and mobile phones.

According to Chinese experts, “Mass extraction of rare earth will cause great damage to the environment and that's why China has tightened controls over rare earth production, exploration and trade,".

Overseas buyers have expressed concern about China's policies to restrict rare earth exports, which have driven up global prices. Rare earths are in increasingly short supply as world demand surges, with industry officials predicting a global shortfall of 30,000 to 50,000 tonnes by 2012.

The automobile industry uses tens of thousands of tons of rare earth elements each year, and advanced military technology depends on these elements, too. Lots of "green" technologies depend on them, including wind turbines, low-energy light bulbs and hybrid car batteries. In fact, much of western civilization depends on rare earth elements such as terbium, lanthanum and neodymium.

If that happens, the western world will be crippled by the collapse of available rare earth elements. Manufacturing of everything from computers and electronics to farm machinery will grind to a halt. Electronics will disappear from the shelves and prices for manufactured goods that depend on these rare elements will skyrocket.

Seeing the possible scarcity of rare earth elements in coming future, India can play major role in REE production. Especially Jharkhand and West Bengal State, which has the potential of good REE in its rocks and inland placers.

Rare earth elements or rare earth metals are a collection of seventeen chemical elements in the periodic table, namely scandium, yttrium, and the fifteen lanthanides. Scandium and yttrium are considered rare earths since they tend to occur in the same ore deposits as the lanthanides and exhibit similar chemical properties. Rare earth minerals occur chiefly in association with alkalic plutons and in placers derived from them. Specific minerals mined for their rare earth or thorium content are monazite and bastnaesite. Despite their high relative abundance, rare earth minerals are more difficult to mine and extract than equivalent sources of transition metals (due in part to their similar chemical properties), making the rare earth elements relatively expensive.

Common Properties of the Rare Earths.

1. The rare earths are silver, silvery-white, or gray metals.
2. The metals have a high luster, but tarnish readily in air.
3. The metals have high electrical conductivity.
4. The rare earths share many common properties. This makes them difficult to separate or even distinguish from each other.
5. There are very small differences in solubility and complex formation between the rare earths.
6. The rare earth metals naturally occur together in minerals (e.g., monazite is a mixed rare earth phosphate).

Indian reserves are predominantly of monazite ore. Monazite contains about 60% of the rare earths of the cerium group expressed as oxide plus an average 7.2% thorium and minor yttrium. It is yellowish to reddish brown mineral. In India, it occurs in commercial concentrations in beach sands.

The pegmatite veins in crystalline rocks contain a few rare earth minerals as their accessory constituents. The most common of these are columbite and tantalite, torbernite, aeschynite, allanite etc. which occur in the mica pegmatite of Hazaribag in Jharkhand State of India. Other places in India are Nellore, Andhra Pradesh and Tranvancore in Kerala and Rajasthan. Gadolinite is found associated with cassiterite in a tourmaline pegmatite in Palanpur; and molybdenite in the crystalline rocks of Chota Nagpur in Jharkhand state.

Geological Survey of India (GSI), during field season 1993-94, carried out detailed study of the north Singhbhum shear zone, in Jharkhand State, with a view to establishing mineral potential including rare earth elements (REE). The results obtained, being not encouraging, similar study in parallel north Purulia shear zone, which is also known as Jhalda shear zone is to be taken up. It extends westward in Ranchi district and is associated with apatite and magnesite mineralization. Recently, some carbonatites with high REE values are reported from this shear zone in West Bengal in India.

In the course of specialized thematic mapping of Chota Nagpur gneissic complex in parts of West Bengal, a few rare metal pegmatites bodies have been identified .Chemical data of these samples show high cesium (1.72 to 13.73%), rubidium (0.27 to 0.33%) and lithium (0.07 to 1.36%).

The world reserve base in terms of rare earth oxides content is estimated at 110 million tones. Although a certain degree of rare earth’s processing exists in a number of countries, the industry is dominated by a few main players like USA, France, Japan and China.

Mineable concentrations of source elements of the rare earth group of metals are uncommon. Bastnaesite is mined extensively in China and the USA. Monazite is recovered largely as a by-product of processing heavy mineral sands in various parts of the world, primarily Australia and India.

Among the inland placer deposits containing heavy mineral, there are two appreciable concentrations of monazite, which are located in Ranchi plateau of Jharkhand and the Purulia planes of West Bengal in India. These occurrences cover an area of about 608 km² , forming a thin cover of an average depth of about 50 cm (which may be locally up to 2 m). These deposits have been formed due to the weathering and erosion of Precambrian gneisses and schists, intruded by pegmatites and porphyritic granits, which are rich in monazite and other associated heavy minerals.

The rare earths are constituents of more than 100 minerals, but only few are recovered. Bastnaesite, monazite, xenotime and rare earth-bearing clays are the principal sources of rare earth supply in the world.

REE are strategic resources upon which entire nations are built. In many ways, they are similar to rubber -- a resource so valuable and important to the world that many experts call it the "fourth most important natural resource in the world," right after water, steel and oil. Without rubber, you couldn't drive your car to work or water your lawn. Many medical technologies would cease to work and virtually all commercial construction would grind to a halt.

Sutiambbe hill in Ranchi city of India is a treasure trove of ancient archaeological sites and geological weathering.

Sutiambe hill in Ranchi city is a treasure trove of ancient archaeological sites and geological weathering.
By
Dr. Nitish Priyadarshi

Sutiambe hill is an archeological site located near Kanke in Ranchi district of Jharkhand State of India.. Formerly, it was the capital of Nagvanshi Dynasty of Chota Nagpur in the first century AD.
There is a remains of the fort of Nagvanshi Dynasty on the hill.
Different Archaeological sites have been discovered like old structures of the Sun Temple, Shiv Temple, the fort of Nagvanshi Dynasty in Sutiambe area. The caves of the first king of the Munda tribe, Maharaja Madra Munda has also been discovered. There is one cave (as shown in the picture) where the rocks inside resembles Shiva Linga and the local villagers offer prayers to these rocks. There are also other mysterious caves in the hills.
This hill not only cradles ancient archaeological remains but it also covered with spectacular geological weathering on the granite gneiss rocks of the hills. This geological weathering resembles very much with the finger prints of some giant ancient animals or a umbrella like hood structure of a hindu mythological snake(cobra or Nagas). Even the caves formed in the hill is a good example of erosional features.
In the picture a small staircase like structure having pot hole filled with water is also seen on the top of the hill. According to the local people king Madra Munda used to use the water from the pot hole for his daily uses. This hole never dries up even during peak summer season. Source of underground water filling this hole is from the hill itself.

Regarding the origin of the Nagvanshi Dynasty a interesting story is told by the historians. It doesn’t have scientific proof but still this story is mentioned several times in the history books written by eminent historians like S.C. Roy and Mangobinda Banerjee.
Though I am a geologist, my purpose of mentioning this story is that during my survey and photography in the area I encountered many erosional and weathering structures which resembles the hood of the giant snakes. From the local people I came to know about the Nagwanshi rulers who ruled this area in the ancient times. Nagvanshi means those who came from the snake family. ‘Nag’ means “cobra snake” and ‘wanshi’ means ‘family’.
Like the Romulas-Remus origin of the Romans, the Chota Nagpur Raj family has preserved an interesting tradition as to origin from the snake, which not only takes us back to the Pauranic times, but seeks to account for the name, “Nagpur”. The story refers to the time of Raja Janmejaya, who in order to destroy the entire race of serpents, celebrated a sarpa-yajna. One of the serpents, Pundarika Nag by name, managed to make good his escape, and, having assumed a human form, traveled to Benares (now Varanasi) and there succeeded in wining the hand of Parvati, the daughter of the learned Brahman. Notwithstanding his otherwise human appearance Pundarika could not, however, get rid of the serpent’s forked tongue which, not long afterwards, attracted the notice of his wife. Parvati naturally became inquisitive about it, and asked her husband what this meant. Pundarika put off answering the inquiry to some future day. And to divert her mind from the subject, he took her on a pilgrimage to the holy temple of Jagannath at Puri in Orissa State. On their way back, they passed through Jharkhand State, as Chotanagpur was then called. Arriving near the hill of Sutiambe in present Ranchi district, Parvati was found to be in the throes of child-birth. And now once more she importuned her husband to tell her the secret of his forked tongue. The explanation could be put off no longer, and Pundarika now gave out his real history and forthwith disappeared in the proper form into a pool of water close by. Parvati in the great agony of mind now began to curse her own womanly inquisitiveness, and immediately after the birth of child, immolated herself on a funeral pyre as befitted a Sati. Just in the nick of time, there turned up a Brahman carrying an idol of Surya-devata, the sungod. The Brahmin was thirsty, and placing his idol by the side of the pool he began to quench his thirst with the pool water. How great was his wonder when, about to resume his journey, he found that the idol could not be moved! He was casting about for an explanation, when, to his astonishment, he noticed a huge cobra protecting a baby from the sun with its hood expanded over the baby’s head! And now the snake revealed himself to the Brahman as Pundarika Naga, and narrated his strange story. The snake went on to prophesy that the child was destined to be Raja (king) of the country. This, child said Pundarika, was to be named Phani Mukut Rai and the country Nagpur. These revelations over, the snake once more returned to the pool and was seen no more. Phani Mukut Rai became the first ruler of Nagvanshi Dynasty.
Purpose of writing this story is not to confuse the scientific world but only to understand whether such features is related to the rulers of the snake dynasty of early first century AD? Is this features are man made or they are the outcome of geological weathering.
Sometimes it becomes essential to correlate the rock structure or rock paintings with civilization, if present at that time.
Whatever the truth is, but seeing the structures on the rocks and different caves in the Sutiambe hill I am sure that this hill will definitely reveal more hidden ancient historical, archeological and even geological facts in coming future.

Reference:

S.C. Roy, 2004. The Mundas and their country. Crown Publications, Ranchi, India.

B. Mangobinda, 1993. An historical outline of Pre-British Chotanagpur [From earliest times to 1765]. Educational Publications, Ranchi, India.

Why Palamau district in Jharkhand State of India faces famine from ancient periods?

Why Palamau district in Jharkhand State of India faces famine from ancient periods?

by

Dr. Nitish Priyadarshi

Palamau district in Jharkhand State of India is reeling under drought. Crops have been destroyed and the region is facing a famine-like situation. In spite of heavy rains in its surrounding districts this year, Palamau district is devoid of sufficient rain. It has not only affected the crops but also depleted the ground water and well water forcing people to drink contaminated water.
Palamau is a district of Jharkhand state, India. The district lies between 23°50′ and 24°8′ north latitude and between 83°55′ and 84°30′ east longitude. It is bordered on the north by river Son and Bihar, on the east by districts of Chatra and Hazaribagh , on the south by Latehar District and on the west by Garhwa District.
The district covers an area of 5043 square kilometers and has a population of 1,533,176.
Daltonganj, situated on North Koel river in the district headquarters. The town is named after Colonel Dalton, Commissioner of Chhota Nagpur in 1861.
The district has been a chronic sufferer from famine, drought, and scarcity conditions from the ancient times. Floods are not a problem as the rivers are mostly hilly excepting Son which is a perennial river and occasionally creates havoc in certain pockets. Cyclones of major intensity are not known.

The Indian Irrigation Commission described Palamau as the driest and probably the poorest district of the province. The frequent draughts and famines or scarcity conditions that have visited this district within the last century support this observation. The district falls within the retreating range of the south-west monsoon and as such rainfall is wholly dependent upon local conditions and local winds which are seldom favourable to the district. Also due to the beautiful Netharhat hill ranges the area comes under rain shadow zone. Rain clouds moving towards Palamau district are trapped within this hills resulting scanty rainfall in the area.

Rain shadow is warm and dry because as moist air masses coming from the Chotanagpur plateau rise to the top of Netharhat hills the air cools and it's temperature decreases until it reaches it's dew point, the point at which the condenses as rain, and then falls either on the windward side or atop the hills. These results in heavy rainfall in the Netharhat area. This is called orographic lifting precipitation. The effect of this phenomenon is the creation of an arid region on the leeward side of hills. Also, the warm air absorbs moisture from the already dry and warm air . The land gets little precipitation because all the moisture is lost on the Netharhat hills. Furthermore, the warm air absorbs moisture from the already dry land.

Within the period of last century there have been famines in 1859-60, 1873-74, 1896-97, 1899-1900 and 1918-19 and there have been several years of scarcity up to 1956 and the worst of all was perhaps that of the year 1955.

The rainfall in Palamau is not only scanty but very capricious in its distribution. There are, it is true, a large number of rivers and streams in the district, but in most of them the supply of water diminishes rapidly or fails entirely soon after the end of the scanty rains.

From old records and reports it will appear that that in 1868 there was a failure of different crops and winter rice due to absence of rain and this caused a famine in 1869. the most affected areas were the north-east and north-west of the district and to a small extent the central areas. In 1873-74, there was again a failure of different local crops and there was a general famine affecting Japla and Belaunja in the north, Deogan and Untari in the extreme north-east and north-west. In 1896 there was again an unfavourable distribution of rain which led to the famine of 1897.
The southern part of this district which overgrown with thick forests and jungles gets more rainfall than the northern part which is almost a plain land bordering district of Gaya. Distribution of rain seems to have been more disturbed from the last five decades. One of the reasons may be the indiscriminate exploitation of forest.

The only solutions to fight such condition is to grow more forest and interlink the rivers through canals.

Earthquakes becoming more frequent in Jharkhand State of India.

Earthquakes becoming more frequent in Jharkhand State.

Dr. Nitish Priyadarshi
Department of Geology
Ranchi University
Ranchi-834001


Introduction:
PHYSIOGRAPHICALLY and tectonically, India can be divided into three broad ones: Peninsular India, Indo-Gangetic plains and the Extra-peninsular India (Himalayas).
The peninsular India comprises shield elements which are supposed to be geologically stable. But earthquakes of Jabalpur and Latur have shown that the shield areas are also prone to earthquakes.

The Chotanagpur Plateau of Jharkhand State represents a part of the Indian Peninsular shield, which is a stable cratonic block of the earth’s crust. Though it is a part of the stable block it is being rocked by mild to medium tremors.
Chotanagpur has faced lots of tremors and geological movements in the geological past and now it is assumed that the plateau is free from any type of tremors or cratonic movement. Evidences of the regional tectonic movement in the plateau area are preserved in the form of faulting, folding, joints etc in the rocks.
Present topographic features of Chotanagpur are clue to the past, and geographers and geologists think that before Himalayan movement started in Tertiary times Chotanagpur and adjoining areas were a low peneplain. As a side effect of the violent Himalayan movements, parts of Peninsular upland in general and Chotanagpur peneplain in particular began to be successively uplifted. The Himalayan movements occurred three times during Early and Late Tertiary and Pleistocene times and probably the Chotanagpur peneplain was also concurrently subjected to three successive uplifts. The line of this block uplift is marked by the steep scarps that surround the Ranchi and upper Hazaribagh plateaus and across which streams descend by well-known waterfalls, e.g. Hundru and Hirni waterfalls.
Damodar valley coalfields have been affected by two phases of fold tectonics. It has been suggested that the major faults and joints present in Damodar Valley coalfield, were formed by block-tectonics, possibly during Tertiary period.

Scientists have found evidence that the oldest earthquake followed by tsunami traceable in the earth's history took place more than 1,600 million years ago in what is now Jharkhand. An international team of scientists from India, Japan and Poland has reported the discovery in a paper to appear in the forthcoming issue of the journal 'Sedimentary Geology.' This occurred long before the massive southern land mass called Gondwana land split up and the piece that now forms peninsular India floated north and crashed in the Asian land mass. The scientists analyzed sedimentary rocks deposited in "Chaibasa Formation" in eastern India. "The layers show deformations that have never been described before," Rajat Mazumder, lead author and currently a Humboldt Fellow in the university of Munich told. Mazumder and co-workers show that earthquakes caused the deformations "while the sediments were still being deposited and before their consolidation," they said. The layers containing these deformation structures are termed "seismites" and the scientists could trace the deformed horizons up to a kilometer depth. Considering their occurrence in sediments deposited between 1,600 and 2,100 million years ago, "they are among the earliest records of earthquakes known in the Earth's history," the scientists reported. "One of the strongest arguments for earthquakes as triggers of the deformation is the occurrence of strongly deformed layers (sandwiched) between unaffected layers of similar grain size," they said. Another argument is the finding of "tabular depressions," the formation of which would have required a large block of sediment to move upwards and drift away. According to the scientists a tsunami generated by an earthquake most likely detached a weakly consolidated silt/mud block and lifted and transported it away leaving behind a hole that gradually got filled by laminated sediment observed by them.

It is interesting to note that Chaibasa Formation is underlain by volcanic rocks which have been dated as 2100 million years old. In other words the sediments of Chaibasa Formation were being deposited in a basin affected by active volcanism. In such areas high intensity earthquakes do occur.
Though "deformation structures" in sedimentary rocks have been observed before, the authors say that in their opinion, those found in eastern India "represent the oldest unambiguous "seismites" that are known from the Earth's history."

Fig: Tectonic map of East Singhbhum

According to GSHAP (Global Seismic Hazard Assessment Program) data, the state of Jharkhand falls in a region of low to high seismic hazard . As per the 2002 Bureau of Indian Standards (BIS) map, this state also falls in Zones II, III & IV. Historically, parts of this state have experienced seismic activity in the M 5.0 range.
Hazard Map of Jharkhand
Significant earthquakes in Jharkhand and its possible causes:

Mild tremors struck Jharkhand Plateau on August 1999 for couple of seconds. Few years back too on July and 21st November 1997 Jharkhand Plateau was rocked by the tremors for few seconds. Due to lack of requisite equipment, the Ranchi Meteorological office was not in a position to say something about the intensity. A tremor stronger than these had shaken Chotanagpur Plateau of Jharkhand on August 21, 1988 at 4.40 AM. The epicenters of the Earthquake was 525 km north west of Shillong ( Indo-Nepal border in Bihar state) and was measured 6.6 on the scale. The 1988 quake which lasted for few seconds was reported from Ranchi, Jamshedpur, Dhanbad and Daltongonj. At Ranchi all windows started rattling. Movements of cots was similar to that in a running train. There was also commotion among birds, and cracks developed in the walls of some houses. Such high intensity earthquake in the Jharkhand State was unnatural. This plateau is peninsular and dead for any crustal adjustment. The high intensity of earthquake in Dharbanga in Bihar State, might have sent tremors to the Jharkhand. One probable cause of the relative strength of shock in Jharkhand, might be transmissibility of the tremors through crystalline rigid and strong crust underlying the Himalayas, the Indo- Gangetic depression, Monghyr region and Jharkhand. The characteristic and consequences of the earthquake of 1988 were similar to those of the shock of January 15, 1934.
The northern Bihar plain falls in the seismic zone of India and is liable to severe earth-quakes as on 15th January 1934.
Due to the devastating Sumatra Earthquake of 26th December 2004 with a magnitude Mw 9.3 Seiches(A seiche is a standing wave in an enclosed or partially enclosed body of water)occurred in the Jharkhand State. Even the Ranchi city felt the tremor.

A mild earthquake struck the adjacent border regions of the districts of Latehar and Lohardagga, Jharkhand, on 21st March 2007 at 22:04 PM local time. It had a magnitude of M?= 3.3 ( M? is magnitude type unknown) and was felt in many parts of the Chota Nagpur Plateau causing minor damage. The earthquake was centred 81.9 kms NW of Ranchi (Jharkhand), India. Tremors were felt strongly at Kuru in Latehar district and woke up many people who were asleep. A few people were reportedly “thrown of” their beds. In parts of Lohardaga district it was experienced for a duration of 5-seconds. Doors and windows rattled under the impact of the tremor and people went outdoors. In Lohardaga cracks developed in the walls of the hostel and other buildings of the Ursuline Woman’s Teacher’s Training College and many windows panes cracked. The strongest tremors were felt in northern parts of Lohardaga town. Houses were shaken at Brahani and Sikni in the Chandwa area of Latehar district. It was also felt for 10-12 seconds at Balumath, Chandwa & Latehar in Latehar district. Here, it was accompanied by the sound of a train and loose objects rattled. A 5-foot crack is thought to have developed outside a house in Chandwa. Elsewhere in the district it was felt at Barwadih, Garu, Mahuadanr and Manika. Many people spent the night outdoors fearing a stronger earthquake would follow. At Chatra, in the district of the same name, people heard doors & windows as well as household articles rattling. Light tremors were felt as far as at Gumla & Sisai in Gumla district, at Bhurkunda (including PTPS), Patratu in Hazaribagh district, Khilari, Mandar & Ranchi in Ranchi district. No damage or injuries have been reported as a result of this earthquake.Rumours of another stronger earthquake at 2 A.M. the following morning resulted in widespread panic in the region. Many people spent the entire night outdoors in the aforementioned areas. In Ranchi, patients were brought out of the hospitals and elsewhere in the region announcements were made from mosques to alert people. Panic spread in areas of adjoining districts, including those that did not experience such as Bhawanathpur, Bishnupur (Gumla), Daltonganj (Palamau), Jhumri Telaiya (Hazaribagh), Hazaribagh, Ramgarh Cantonment and Simdega.

Jamshedpur and its adjoining areas experienced at least four low-intensity tremors in the month of January, 2008. According to the different experts the tremors could well be due to the heavy rainfall that occurred last year 2007. Rain water percolating into the soil may have provided a cushion for the smaller plates to move causing earthquakes.

Huge downpours of rain can trigger earthquakes in landscapes riddled with caves and channels by increasing pressure within underlying rock, suggests a new study.
It was already known that rainfall could cause tremors, but the amount of water needed is much more than previously thought, says Steve Miller, a geologist at the University of Bonn, Germany.
In recent years, geologists have documented small earthquakes that occurred after heavy rainfall in Germany, Switzerland and France. All were low in magnitude – meaning they could be detected by seismographs, but not felt by humans.
Some experts have suggested that although the rainfall was heavy, the fact that rain could trigger an earthquake at all suggests that it takes extremely little to produce a tremor. They concluded that the Earth's crust in a delicate balance, teetering on the edge of a slight shake-up at any moment.

According to me there are possibilities that construction of large water dams, water reservoirs, different types of mining and increasing use of groundwater (which is creating vacuum inside the earth) in and around Jharkhand are major reason why these earthquakes are occurring at such frequent intervals.
Severe earthquakes can be triggered by dewatering and flooding of mines, as these activities alter the loading of the Earth’s crust and tectonic stresses in its interior. Worldwide, more than 200 studies have noted sites where human-induced stresses could have reactivated preexisting faults, triggering earthquakes with seismic moment magnitudes of up to M = 7 on the Richter scale. This can only occur where faults are already under high tectonic stresses that have built up over many years. Stable continental regions are seismically less active than unstable regions (e.g. California, Japan, and Turkey). Consequently, faults in stable continental regions can be more earthquake-trigger sensitive, since accumulated stresses have not reached failure conditions.

After becoming the new state there is boom in building industry. Lots of multistoried buildings are being built in the capital city of Jharkhand on the highly metamorphosed rocks filled with numerous joints and fractures. Very few people go for soil or rock testing before constructing huge buildings which is very essential. These constructions may disturb the balance (isostasy) of the local rock types. Stress from the skyscraper may re-open ancient earthquake fault.
Though stress and strain developing on the rocks can also be treated as the major cause of the earthquakes.

From last couple of years Jharkhand has felt few tremors in different parts of the State of low intensity and unfortunately due to its localized occurrence its intensity was not recorded.

Other causes of Earthquakes in Jharkhand:

Earthquakes of Jharkhand may be placed in one broad categories. Earthquakes originate from stress fields built up in the Precambrian shield, supporting the Vindhyan, Gondwana and younger basins.
Several events such as the 1868 Hazaribagh, 1963 Ranchi and 1969 Bankura were generated by release of stress built up in the relatively more stable Jharkhand Plateau region underlain by Precambrian formations. These, by analogy with other Peninsular Shield events such as Latur and Jabalpur earthquakes, may possible belong to the class of Stable Continental Earthquakes. This class of intraplate earthquakes occur in areas characterized by antiquity (2.5-0.5 billion years), much lower deformation rates compared to the more active regions of the intraplate regions and therefore longer periods of recurrence, reduced heat flow, greater average crustal thickness and low elastic attenuation. Several parameters of the earthquakes of the region are still not known and the classification here is, therefore, tentative.
Regarding the type of earthquakes occurring in State it may be placed under “Shallow Earthquakes” ("Crustal" quakes) which are caused by faults in the continental plates, as a result from the relative motion of sections of the plates. They are usually 1 to 5 magnitude, less than 15 miles deep, occur random and unpredictable and most of them are not even felt.

The Tatapani Fault in the western part of the state has been active since the Holocene period and extends across the border into the neighbouring state of Chhattisgarh. The Munger-Saharsa Ridge Marginal Fault runs in a north-south direction through the eastern districts of the state before entering West Bengal. However it must be stated that proximity to faults does not necessarily translate into a higher hazard as compared to areas located further away, as damage from earthquakes depends on numerous factors such as subsurface geology as well as adherence to the building codes.
Possibilities of major earthquake in this stable region cannot be ruled out. Different researches has shown that ancient fault line can be re-activated. Old continental crust contains a billion-year record of past tectonic activity. This area was once a seismically active. "We don't yet understand how faults are reactivated, but it appears that some pre-existing faults are more likely to break than others. Regarding Jharkhand the possibility of reactivation of a pre-existing fault can happen under the influence of the ambient stress field due to the India–Eurasia plate collision forces.



Reference:

Rajat Mazumder, A.J. (Tom) van Loon and Makoto Arima (2006)Sedimentary
Geology, Volume 186, Issues 1-2, Pages 19-26
Mahadevan, T.M., 2002. Geology of Bihar & Jharkhand. Geological Society of India, Bangalore.

http://www.boloji.com/environment/58.htm
http://environment.newscientist.com/article/dn13371-heavy-rain-can-trigger-earthquakes.html
http://asc-india.org/maps/hazard/haz-jharkhand.htm
http://www.springerlink.com/content/r0765k18488l23lk/
http://www.scienceblog.com/cms/ancient_fault_lines_may_have_become_re-activated.

N. Purnachandra Rao,T. Tsukuda, M. Kosuga, S. C. Bhatia and G. Suresh, 2002. Deep lower crustal earthquakes in central India: inferences from analysis of regional broadband data of the 1997 May 21, Jabalpur earthquake. Geophysical Journal International Volume 148 Issue 1 Page 132-138.


Dr. Nitish Priyadarshi
76,circular road,
Ranchi-834001
Jharkhand
India
Email: rch_nitishp@sancharnet.in