Oldest Tsunami occurred in Jharkhand State of India more than 1,600 million years ago.

The scientists analyzed sedimentary rocks deposited in "Chaibasa Formation" in eastern India.
by
Dr. Nitish Priyadarshi

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 of the journal 'Sedimentary Geology’ in year 2006.

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 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.



The high grade Chaibasa Formation is estimated to have 2-4 km of thickness and is traceable westward to the north of the Chakradharpur town South of Ranchi city. The character of the sediments in the Chaibasa Formation, the non-diastropic structures preserved in them, despite extensive but open folding and deformation, and the environment of deposition have received some attention. Deep to shallow marine turbidite environment, peritidal shallow marine environment or even a totally fluvial environment have been proposed. Perhaps more than one environment co exists in the region.

S.M. Mathur in1964 and K. Naha in 1956 are among the earliest geologist to suggest turbidite structures and a deep marine environment in the Ghatsila area. M.V.N. Murthy and Anand Alwar in 1966 recorded some 106 cycles of turbidite beds in a 3500 m thick arenaceous pelite sequence in the Subarnarekha river section north of Rakha mines. It is suspected that such cyclic turbidite sequence may be related to seismic phenomena. Sedimentation in the Singhbhum Mobile Belt is endowed with several features. Both tectonism related to lithospheric stretching and contemporaneous volcanism are reflected in the character of the sediments.

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 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.

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.

Though being a stable zone, 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.

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. Jamshedpur and its adjoining areas experienced at least four low-intensity tremors in the month of January, 2008. This year in month of January mild tremors were in felt in parts of Shaebganj, Pankur, Godda, Ranchi district etc.

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.

Geobotanical methods for prospecting uranium deposits.

Plants can also help us in finding uranium.
by

Dr. Nitish Priyadarshi

Fig. Aster Venusta

Name of the plant in the figure below is Astraqualus sp.

Geobotanical methods of prospecting involve the use of vegetation for identification of the nature and properties of the substrate. Paradoxically, these methods are among the easiest to execute and yet the most difficult to interpret of all the methods of exploration available at the present time. In terms of execution, the basic requirement is merely a pair of human eyes; but in the interpretation of the visual (or photographic) image, some knowledge is required of a number of different disciplines such as biochemistry, botany, chemistry, ecology, geology, and plant physiology.

Geobotanical methods of prospecting are based on the visual observation and identification of vegetation or plant cover that may reveal the presence of a specific type of sub-surface mineralization. In this method, it is presumed that a particular variety of plant species is an indicator of a sub-surface uranium molecules. In recent years, geobotanical methods have become useful in the identification of uranium- ore deposits particularly in areas of dense vegetation.

The method dates back to the eight or ninth century, when the Chinese had observed the association of certain plant species with mineral deposits. In the early nineteenth century, the Russian geologist, Karpinsky observed that different plants or plant communities could be indicators of rock formations and that the characteristics of the plants of an area could be used to decipher the geology of the area. The method has evolved over the years and now more than a hundred species have been recognized as indicators of the presence of a number of elements, including ore metals.

Two distinct approaches to geobotanical prospecting for uranium have been developed to cope with specific problems of exploration. The first method is based upon the presence of uranium in all plants in small but measurable amounts. It has been observed that the uranium content of plants rooted in mineralized ground is detectably higher than the uranium content of plants rooted in unmineralized ground. Plant ash is analyzed directly for the determination of uranium content. The uranium content of the ash of plants growing above unmineralized formations is generally less than 1 ppm, whereas that of the plants rooted in ore bodies contain several parts per million (ppm). This technique helps in the broad outlining of mineralized areas.

The second method involves mapping the distribution of certain indicator plants growing in ecologically favourable areas. A plant may be used as an indicator, provided it is established that its growth is controlled by certain factors which are related to the chemistry of the ore deposit. The sandstone type of uranium deposit contains an appreciable amount of selenium and sulphur. The distribution pattern of plants, which require one of these elements for normal growth, may indicate favourable ground for sub-surface uranium mineralization. Plant morphology and physiology are profoundly influenced by the chemical composition of sub-surface ore bodies and groundwater regime.

This method has been used in the USA for locating sandstone type of uranium deposits, particularly in areas where surface expression is lacking. Astragalus pattersoni, which thrives on the direct intake of selenium from ore bodies located up to a depth of 75 feet, was identified as one of the indicator plants for uranium.

Prospecting by both plant analysis and indicator plant mapping in widely separated areas of the Colorado plateau has shown a positive correlation between botanically favourable ground and major ore deposits.

Geobotanical surveys have been carried out in the Satpura-Gondwana basin of Madhya Pradesh and the foot hills of the Himalayas to demarcate mineralized (uranium) sandstone facies. Surveys conducted in the Kangoo basin of Hamirpur district in Himachal Pradesh revealed uranium values in plant ash samples ranging from 4.3 ppm to 96 ppm. Two- fern plants belonging to Adiantum venustum analyzed uranium values of 194 and 634 ppm respectively.

Perhaps the most obvious of all plant mutations is that of changes in the colour of the flowers. Colour changes in flowers are usually the result of either radioactivity or of the presence of certain elements in the soils.

Metal ions as well as radioactivity can affect the colour of flowers. The gardener’s trick of adding iron or aluminium to red hydrangeas to turn them blue is of course well known. The theory behind such colour changes is interesting and may have bearing on mineral exploration.

The majority of flower colours are produced by a surprisingly small number of pigments. Apart from Carotenoids, which are important in yellow and orange flowers, it is mainly the anthocyanins that are responsible for the colour range from orange to deep blue. It was suggested that in the absence of certain metals, the anthocyanins for red oxonium salts which become blue when they are complexed with excessive amounts of iron, aluminium, or other elements.

Besides iron and aluminium, other elements such as chromium and uranium can form stable complexes with anthocyanins. It is therefore possible that excessive amounts of some of these metals could produce a blue tint in flowers that are normally red or pink, and this could be useful field guide in prospecting.

Unusual and unpredictable changes of form are produced by radioactivity. The first result of mild doses of radioactivity is a stimulatory effect on the vegetation. After the nuclear explosion at Hiroshima, exceptional yields of various crops were obtained.

Fortunately, however, natural radiation is never as high as that encountered at Hiroshima in 1945 and levels normally encountered are therefore seldom sufficient to produce an obvious stimulatory effect on vegetation. There is, however, ample evidence that even fairly low levels of radiation can produce morphological changes in plants over a prolonged period. Variations was found in fruit of the bog bilberry ( vaccinium uliginosum) growing in a radioactive area at Great Bear Lake in Canada.

Plants are the only parts of the prospecting prism which extend through several of the layers simultaneously. It is claimed that the main advantage of biogeochemical prospecting compared with other geochemical methods lies in its power of penetration through a non mineralized over burden.

Reference:

Brooks, R.R., 1972. Geobotany and biogeochemistry in mineral exploration. Harper and Row publishers, New York.

Virnave, S.N. 1999. Nuclear geology and atomic mineral resources. Bharati Bhavan, Patna.

Ancient climate indicator rocks are also found in Jharkhand State of India.

The formation of some rock types and minerals are directly influenced by aspects of climate.

by

Dr. Nitish Priyadarshi

Palaeoclimatology, the study of climates during the geological past, is one of the most topical areas of research in the geosciences at present. The threat of future climate change caused by higher levels of greenhouse gases, which would drastically alter many aspects of our environment, has prompted much research to try to understand how our complex climate system works. Only by understanding how climate has evolved over million of years can we identify important climate cycles with a frequency in excess of the short climate records we possess. These climate cycles have the potential to have a profound effect on our environment.

Understanding our climate history in the geological past is also important for climatologists trying to construct accurate numerical computer models of our present climate system to use for predicting future climate change.

Basic information about past climates comes from understanding how climate influences certain sedimentary systems, floras and faunas on earth today and extrapolating this information back to interpret geological evidence.

The formation of some rock types and minerals are directly influenced by aspects of climate. Some of the most useful are coals, evaporates, glacial deposits, Bauxite and carbonates. I am presenting only a brief resume of rocks and minerals as a paleoclimatic indicators in Jharkhand State of India.

Coal:
Coal is a compact stratified organic rock composed largely of metamorphosed plant remains mixed with a variable but subordinate amount of inorganic material. The coal-forming plant material may have accumulated where it grew or may have been transported to the depositional site by water or wind. The accumulation of peat requires a humid climate to support a rich growth of vegetation and a high water table to permit prolonged accumulation of plant material in a reducing environment. In other words, the presence of coal, initially formed from the accumulation of plant material as peat, is generally taken to indicate warm and wet humid climates ideal for lush plant growth, and where the rainfall is higher than the rate of evaporation, such as in equatorial regions.

In the past, the most abundant coal deposits were formed during the Carboniferous when large subsiding continental areas were situated in low latitudes and experienced hot and humid climates. The great Carboniferous forests were composed of the pithy-stemmed clubmosses and lycopods, such as Lepidodendron, Siggillaria and Calamites, which grew to giant sizes in the hot wet conditions and formed thick layers of peat as they collapsed into waterlogged swamps. The disappearance or decrease in size of these water loving plants at the end of the Carboniferous marked the onset of much drier conditions in low-latitude regions during the Permian.

A discussion on depositional environment of Permian peat swamps phases may well be preceded by the remarks that, Karharbari, Barakar and Raniganj ( these are all different coal formation stage) stages of Lower Gondwanas of Jharkhand State of India, were climatically controlled. The climate during Karharbari period was rather cold as evidenced by flora and by possible effects of glaciation in Talchir series. On the contrary, climate during Barakar and Raniganj commenced with coal and humid climate gradually becoming warmer and humid as evidenced by flora and coal composition.

Glacial deposits:

Evidence for glaciation and the presence of thick ice sheets can be obtained from a variety of sources. The most convincing are striated pavements, that is surfaces of bedrock with grooves scratched by debris frozen into the base of moving ice glaciers. The orientation of ice movement and therefore in some cases the position of glacial centres can also be determined. Till or tillites can also provide information about ice passage. The term till was originally applied in Scotland to a stiff, hard clay subsoil, generally impervious and unstratified, often containing gravel and boulders. In present usage, the word till means a clastic glacial deposit, usually poorly sorted and nonstratified, and derived from glacial drift; it consists of a heterogeneous mixture of rock and mineral fragments of varied lithologic composition, size and shape. If till is indurated by cementation or metamorphism, it is called tillite.

Evidences of tillites are found in different coalfields area of Jharkhand State.

Bauxite:
Bauxite is not a product of normal weathering in temperate regions, it is almost entirely lacking from soils formed there. It is however, a constituent of laterite soils formed in tropical and subtropical regions. They have mostly been formed in the late Mesozoic or Tertiary time under climate conditions different from those that prevail in the same places today. Possibly some of the conditions that affected the change from the age of reptiles to the age of mammals likewise promoted the formation of bauxite.

The conditions necessary for bauxite deposits are humid tropical or subtropical climate. It has been shown that a temperature above 20 degree C favors chemical processes by which SiO2 goes into solution and Fe2O3 and Al2O3 remain behind. The wet season of the tropics is one of formation of Al2O3 and Fe2O3, the dry season one of leaching of silica away from these oxides. This may supply the answer to why a tropical climate is necessary for bauxite formation.
Bauxite are found in Lohardaga and Netharhat areas of Jharkhand State.

PROSPECTS OF COAL BED METHANE GAS IN JHARKHAND STATE OF INDIA.

PROSPECTS OF COAL BED METHANE GAS IN JHARKHAND STATE OF INDIA.

By
Dr. Nitish Priyadarshi


Coal contains methane gas as an inherent component but in widely variable proportions depending on the rank of coal and depth of occurrence. Its presence in coal has so far been considered a hazard as it is an inflammable and explosive gas and there have been many fire accidents in coal mines throughout the world due to this gas. In recent years, coal bed methane has become a good source of clean thermal energy for its easy inflammability and it has come up as an additional energy resource from the coal basins especially in the countries like USA, Australia and China.

Deep seated coal seams of comparatively high rank contain considerable volume of methane adsorbed on coal surfaces.

Unlike much natural gas from conventional reservoirs, coal bed methane contains very little heavier hydrocarbons such as propane or butane, and no natural gas condensate. It often contains up to a few percent carbon dioxide.
India is struggling to find enough energy sources to meet up the growing energy demand coupled with economic growth. Indian government is now exploring alternative sources too. Indian government has received 54 bids to extract coal-bed methane (CBM) from various domestic and foreign energy companies. This is the highest amount of bids the government has ever received. 18 domestic companies and 8 foreign companies have submitted their bids to extract methane from ten areas. It shows CBM has a good prospect in India.

At present, many foreign companies are setting up their plants in India. In addition, Indian companies are targeting the global market. This rapid industrialization has made India an energy hungry country. As the price of oil continues remain high in the international market, CBM can be a good source of energy for India in future. In fact, India is going to start commercial production of CBM from 2007. Some states of India contains good reserve of coal.

The prospect for coal bed methane is mainly related to the coal resources of the country. India has huge Gondwana (mainly Permian, 99.5%) and Tertiary (Eocene and Oligocene) coal deposits distributed in several basins located in peninsular and extra-peninsular regions. About 204 billion tons of coal reserves have been established and approximately 200 million tons or so are likely to be added in the near future by further explorations.

CBM IN JHARKHAND:

In India prospects of Coal Bed Methane (CBM) is not very bright, as most of the Indian coals are of inferior quality and of low rank. However, some of the coal basins contain high rank coal where sizeable reserves of CBM may be expected. A recent assessment has identified certain areas of Gondwana coalfields where gas -in-place reserves of 564 billion cubic meters have been indicated.

In 1990, efforts to exploit coal bed methane were initiated by Essar Oil (a private oil company) under the advice of American experts. The methane emission and desorption studies on Gondwana coal samples from Jharia Coalfield (Jharkhand) were carried out by Central Mine Planning and Design Institute Limited (Ranchi) and Central Mining Research Institute (Dhanbad). The content of gas and gas emission rate from these samples were found to be 1.8–2.3 m3/1000 m2 of surface and 12.7–17.3 m3/min, respectively. The studies carried out by Bharat Coking Coal Limited in the same area with the help of French experts indicated 0.68–1.45 m3/min gas emission rate.

In Jharkhand State areas identified for CBM are Jharia, East Bokaro, West Bokaro, North Karanpura and Rajmahal Basins.

The estimate reserves in Jharia coalfield is 4.82 trillion cubic feet, in East Bokaro it is 3.2 trillion cubic feet and West Bokaro it is 0.38 trillion cubic feet. Some of the new areas has also been identified like North Karanpura coalfield for the CBM which needs more survey.

Potential of CBM production in Jharia coalfield is 3.5 million cubic metres/day , East Bokaro has the potential of 2.5 million cubic metres /day, North Karanpura has the potential of 6.0 cubic metres /day and the Rajmahal Basin has the potential of 4.5 cubic metres/day.

Thick Tertiary coal of Makum area, Assam, and thick lignite seams of Tamil Nadu and Gujarat may also be positive areas for methane prospects. These factors need to be considered in future.

Reference:

Acharyya, S.K. Coal and Lignite Resources of India,2000, 41-43.
Biswas, S. K., Indian J. Petrol. Geol., 1995, 4, 1–23.
http://www.cmpdi.nic.in/cbm.htm
http://www.iisc.ernet.in/currsci/jun25/articles15.htm

http://envfor.nic.in/cpcb/newsletter/coal/cmetha.html

http://www.indianraj.com/2006/07/coalbed_methane_cbm_indias_fut.html

Coals are best indicators of ancient climate

Coals are best indicators of ancient climate.

By

Dr. Nitish Priyadarshi
Palaeoclimatology, the study of climates during the geological past, is one of the most topical areas of research in the geosciences at present. The threat of future climate change caused by higher levels of greenhouse gases, which would drastically alter many aspects of our environment, has prompted much research to try to understand how our complex climate system works. Only by understanding how climate has evolved over million of years can we identify important climate cycles with a frequency in excess of the short climate records we possess. These climate cycles have the potential to have a profound effect on our environment.

Understanding our climate history in the geological past is also important for climatologists trying to construct accurate numerical computer models of our present climate system to use for predicting future climate change.

Basic information about past climates comes from understanding how climate influences certain sedimentary systems, floras and faunas on earth today and extrapolating this information back to interpret geological evidence.
The formation of some rock types is directly influenced by aspects of climate. Some of the most useful are coals, evaporates, glacial deposits and carbonates. I am presenting only a brief resume of coal as a paleoclimatic indicators.

Coal- climatically sensitive rock:

The presence of coal, initially formed from the accumulation of plant material as peat, is generally taken to indicate warm and wet humid climates ideal for lush plant growth, and where the rainfall is higher than the rate of evaporation, such as in equatorial regions. However, rainfall is more important factor than temperatures, as are high water tables and waterlogged swamps (mires) which are required to preserve the peat.
Coal seams are composed of genetic coal types which are determined to a certain extent by the character of the particular type of vegetation. A careful analysis of all the available data on geochemical, palynological and petrological constituents of the coals reveals that there existed distinctive types of vegetation associated with different peat types. The character and relation between the miospore assemblage and petrographic type reflect particular environment, topography and climatic conditions.
Pollen and spores commonly retain their morphological characteristics through all stages of coal formation. They bear specific relationship to the original geological and botanical setting.

In the past, the most abundant coal deposits were formed during the Carboniferous when large subsiding continental areas were situated in low latitudes and experienced hot and humid climates. The great Carboniferous forests were composed of the pithy-stemmed clubmosses and lycopods, such as Lepidodnedron, Sigillaria and Calamites, which grew to giant sizes in the hot wet conditions and formed thick layers of peat as they collapsed into waterlogged swamps. The disappearance or decrease in size of these water- loving plants at the end of the Carboniferous marked the onset of much drier conditions in low latitude regions during the Permian. Extensive forests dominated by glossopterid plants lived on all southern continents and their remains form extensive and some economically important and coal deposits today.

A discussion on depositional environment of Permian peat swamp phases may well be preceded by the remarks that, based on different analysis and support from geological setup, Karharbari, Barakar, and Raniganj Stages of Lower Gondwanas of India were climatically controlled. The climate during the Karharbari period was rather cold as evidenced by flora and by possible effects of glaciation in Talchir Series. On the contrary, climate during Barakar and Raniganj commenced with cool and humid climate gradually becoming warmer and humid as evidenced by flora and coal composition. Humidity seems to have recurred in some part of Raniganj Stage also.
In the early period of the Permian, coal formation took place under the relatively cold, humid, shallow water deposition mainly from arborescent vegetation.

Chemistry of Coal-bed and paleoclimate:

The chemical arguments for the interpretation of paleoclimate from coal beds come principally from the work of different geologists. Their work was partly in response to studies purporting to show that high-sulfur coals were influenced by marine sedimentation. They argued that peat that forms economic coal cannot form in seawater because ash and sulfur enrichment is too great there. Thus they concluded that all economic coals were originally freshwater peats. They further concluded that, if all economic coal beds were derived from freshwater peats, ash content must be indicative of climate, and they proposed the following model, which predicts three types of peat:
1. anaerobic (permanently waterlogged) peat with pH less than 4.5, which would give rise to low-ash, low-sulfur, vitrinite-rich coals;
2. anaerobic with pH greater than 4.5, which would give rise to high-ash, high-sulfur, liptinite-rich coals; and
3. intermittently aerobic peat, which would give rise to low-sulfur, moderately high-ash, inertinite-rich coals.
Boron element in coal as a Paleosalinity Indicator:
The concentration of boron in Australian and Canadian coals was determined in order to assess the variation of boron in coal with respect to rank, age, geological setting and the degree of paleosalinity of the coal forming environment. The boron content of seams is sensitive to the environment of deposition and may show the variation in the same seam laterally due to changes to the environment of deposition and /or the enrichment of boron by secondary source.
It is proposed that the following ranges of values for boron in coal indicate the degree of marine influence during the early stages of coalification:
1. up to 50 ppm (parts per million) boron- coal formed in a freshwater environment.
2. 50 to 110 ppm boron – coal formed in a mildly brackish water environment.
3. greater than 110 ppm boron- coal formed in a brackish water environment.
Coal petrography and paleoclimate:
Vitrinite-rich coal beds are generally regarded to have been deposited in wet conditions, usually meaning high water tables, especially if the coal beds have clay partings and inclusions of syngenetic pyrite . Inertinite-rich coal beds are generally regarded to have been deposited in dry conditions, usually meaning relatively low or fluctuating water tables.

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