eChapters

Abstract

Indian Peninsular shield has been thought as tectonically inert and aseismic for many years by the Geoscientists. But, subsequent to the disastrous earthquakes in Killari, Jabalpur and Kutch, studies have been initiated in multiple directions on various aspects of seismicities. The present study is aimed at bringing out a possible picture on the seismic vulnerability of parts of Westernghats of Tamil Nadu using various tectano geomorphic anomalies like unifrequency lineaments and different levels of dissection of plateaus, denudational geomorphic anomalies like anomalous talus materials and fluvial geomorphic anomalies like radial drainages, compressed meanders, eyed drainages and wider flood plains interpreted from the raw and digitally processed Landsat TM and IRS P6 LISS-III satellite datasets. The subsequent generation of individual GIS layers on these anomalies and their integration revealed that the N-S faults are tectonically active and the NE-SW and NNE-SSW faults are active faults. Many earthquake epicenters were also found to fall along these lineaments / faults.

Introduction

The Indian peninsular shield, exposing the Archaeozoie - Proterozoic piles of rocks, is known for its tectonic inertness and the related land stability. Owing to such shield area character, the geoscientists were also having strong convictions for a long time that seismically the area is safe.

Abstract

The coastal regions are always tectonically active since these form the junction between the continental and oceanic plates. These tectonic activities and the resultantly tutored fluvial and marine geomorphic processes and the independent fluvial and marine geomorphic processes carve out the coastal morphology. And if these coastal geomorphic features are studied, it will lead to the understanding of the morphotechtonics. One such a study carried out for a part of Ganjam coast, revealed various geomorphic anomalies viz: presence of high order hill ranges only in the north eastern and south western parts of the area with the central plain, northerly migrating Ganjam river, development of wide beach ridges only along the central plain, all indicating the Late Quaternary upliftment of the central plain.

Introduction

The Indian subcontinent is vested with nearly 9,000km long coastline both in its eastern and the western continental margins. These coasts provide unique configuration with convexities (land protruding into the coast), concavities (vice-versa), deltas of different morphologies, beach ridges and swales, bay mouth bars, peaks, serrations and projections in the shorelines, all indicating the vibrant tectonic, fluvial, marine and aeolian processes. As the coastal zones in general, form the boundaries between the continental and oceanic plate margins, these are inherent weak zones prone to tectonic activities, which in conjunction with other geomorphic processes, provide unique architecture to the coasts with above varied geomorphic features. That too, the Indian coasts were inferred to stand as testimony to the vibrant tectonic activities and other related geodynamic processes of the Quaternary period (Ramasamy, 1989; Ramasamy, 1999).

Abstract

The frequently recurring earth tremors / Seismicities in parts of Tamil Nadu & Kerala and the earthquakes of higher magnitude in Central India in the recent years have gradually dissolved the concept of shield area stability for the South India and the concept of mid-plate seismicity has emerged in the minds of geoscientists, Hence, the geoscientists have embarked into a number of studies to bringout seismotectonic maps for South India. In this context, a detailed studies have been carried out by the authors in parts of westernghats (Kodaikkanal and Varushanad hills) in Tamil Nadu. In the said study lineaments were interpreted using high resolution IRS satellite data and from the lineament pattern, isofracture, lineament density and lineament interaction intensity the strain maxima axes were drawn. Such strain maximas were observed to fall in N- S, E – W and NE –SW directions. These strain maximas were found to coincide with various drainage anomalies, like radial, compressed meandering and eyed drainages indicating that these lineaments are prone for seismicity/ earth tremors.

Abstract

Being the junction between the continental and the oceanic plates, the coastal zones are always tectonically alert and hence vested with number of aults. The study of LANDSAT ETM FCC imagery revealed one such a major fault along NNE-SSW aligned Tamil Nadu coast from Chennai in the North northeast to Cape Comorin in the South southwest. This Precambrian boundary fault shows signs of repetitive reactivation during Gondwana, Tertiary and Late Holocene periods. While in former two periods it shows indications of faulting, in the latter period, it is manifested in the form of drainage deflections indicating sinistral movements of beds. While such sinistral morphology of the fault seems to be related to the Post collision compression, the seismicities in and in its close proximities indicate the seismic significance of this fault. In the context of natural resources and disasters viz: geothermal springs, flooding and seismicities, this fault demands deeper studies.

Introduction

The coastal regions in general form the junction between the continental and oceanic plates. Hence, the coastal regions are always tectonically active and thus vested with coast parallel, tangential and conjugate faults depending upon the tectonic history of the area. In the Indian subcontinent too, all along the 9000 km long east and west coast margins, number of major faults were mapped by the earlier workers. Significantly, Vardarajan and Ganju (1989) have brought out a comprehensive picture on the lineaments of the entire coastal zone of India using Landsat images. Vemban et al. (1977) earlier inferred faults along certain segments of east coast of Tamil Nadu and observed them to be lithological contacts and also seismogenic in nature. Raiverman et al. (1966) have again inferred earlier a N-S curvilinear fault in Thanjavur deltaic region and attributed it to post drift kinematics of the Indian plate. Ramasamy (1989) has brought out the morphotectonic and morphodynamic model of the east and west coasts of India on the basis of tectonic and geomorphic signatures using Landsat satellite images. Ramasamy (2006) developed a first time comprehensive model on the active tectonics of the Indian Peninsular and in which he brought out detailed information on the varied geomorphic, tectonic and hydrological anomalies and inferred them to be related to the whirling and fracturing of the Indian plate due to the still prevailing N–S to NNE – SSw compressive force which originally drifted the Indian plate to the present position after the breakup of the Gondwana land.

Abstract

The drainage pattern and the architecture are the reflections of not only the tectono fabric of a region, but also the active tectonic processes. From amongst many drainage patterns and anomalies, the eyed drainages, deflected drainages and the compressed meanders interpreted from satellite images for Pudukkottai region of Southern Tamil Nadu infer to reflect the active N-S block faults and NE-SW sinistral and NW-SE dextral faults related to post collision tectonic phenomena.

Introduction

The Geoscientists have long back recognized that the drainages are the reflections of the surface and subsurface lithology, structure and tectano fabric and also the active tectonic movements especially of the Quaternary period (Thornbury, 1985). Hence, the Geoscientists have all along been showing greater interest in mapping the drainage patterns. However, the mapping of the drainage patterns and detection of tectonic features there from have gained greater momentum only after the advent of modern Remote Sensing technology. Since the airborne and satellite borne spectral images have the credentials of showing the drainage pattern, the drainage anomalies and the tectonic features related to them all of which were studied in conjunction to bring out information on the geological history of the Quaternary period by many workers (Vaidyanadhan, 1971; Murthy and Sastri, 1981; Agarwal and Mitra, 1991; Ramasamy, 1991; Saravanavel and Ramasamy, 2014).

Abstract

The Cauvery delta is a major bird-foot shaped delta with its apex located east of Tiruchirappalli with the mother channel Cauvery flowing along Thanjavur– Kumbakonam – Kaveripoompattinam. The distributary drainages are radiating over an arc towards east from its apex with a fan shape and finally debouch into the sea from south of Tiruthuraipoondi in the south to Kaveripoompattinam in the north. All these distributary drainages are now seen as palaeochannels including the mother channel Cauvery, which is now called as “Palam Cauvery”. The present day flow of Cauvery river is confined to the northernmost rim of the delta as river Coleroon. On the basis of the archaeological, epigraphic and historical data analysed earlier and the14C dating carried out recently, the present authors infer that the age of the delta may vary from 2300 Y.B.P. ( Years Before Present) to 750 Y.B.P. and the age of the palaeochannels are also younging from 2300 Y.B.P. in the south to 750 Y.B.P. in the north. In the southern part of the Cauvery delta, the Mio-Pliocene Sandstone of Pattukottai-Mannargudi area is undergoing upliftment along N-S faults. On the basis of the rapid land progradation during 6085±233 Y.B.P. - 1020±80 Y.B.P. in Vedaranniyam coast, it is visualized that the Mio-Pliocene Sandstone must be undergoing upliftment significantly since 6100 Y.B.P. onwards. On the basis of the occurrence of older palaeochannels in the south, the gradual younging palaeochannels towards the north and the land emergence in the south of the Cauvery delta in Pattukottai – Mannargudi area, it is concluded that the distributary drainages of river Cauvery would have become sequentially defunct / shifted from south to north and finally the mother channel Cauvery also would have been pushed towards north to reach the present tract of Coleroon river. The thinner palaeochannels in the south and the gradual wider palaeochannels in the north of the delta further indicate that as the land was already undergoing emergence in the south even before river Cauvery has entered into Thanjavur plains, the river could not comfortably spread its distributaries in the south. Hence, the southern distributaries, after a brief flow, would have started drying sequentially from south to north during 2300–750 Y.B.P. thereby the floodwater of each of the southern distributary channel would have been pushed to its successive northern counterpart, i.e. the southern distributary (say 1), pushing its water to its immediate northern counterpart (say 2), then the combined flow of 1 and 2 pushing the water to 3 and so on. The anomalous eyed drainage and its modifications during the last 50–60 years and compressed meanders in Coleroon river, deflected drainages in Palam Cauvery, truncation and punctuation of beach ridges by the E – W faults along the N – S coast and such faults acting as pathways for the sub parallel creeks indicate vibrant Late Holocene geological history predominated by the tectonic movements in Cauvery delta.

Abstract

Overall geological histories of the Quaternary deltas of all over the world have been studied considerably, to understand the evolution, eustatic – isostatic changes, land – ocean interactive phenomenon, resources, environment etc. But tectonic signatures of these deltas have been less studied, though these have significance in understanding the natural resources, environment and evaluation of natural disasters. In this context, as the state of Tamil Nadu is a low easterly gradient plain, all the easterly flowing rivers have developed well evolved geomorphic features related to youthful, mature and old stages. Such old stages of the rivers are marked by the spectacular development of deltas. These deltas of Tamil Nadu have been studied in detail for understanding the tectonics with the help of visibly seen tectonic and geomorphic features in satellite based remote sensing and ground based data sets. The study has revealed that the upper age limit / ages of these deltas are probably of Middle to Late Holocene and the various tectonic and geomorphic anomalies observed in these deltas obviously indicate the tectonic processes/ phenomena that prevailed during Middle Holocene - till date. The Proto Cauvery delta of Chennai region is witnessing ongoing NE–SW sinistral, NW–SE dextral and E–W vertical tectonic activities. The streams in Ponnaiyar delta are showing persistent southerly migration due to the probable ongoing land subsidence along NE–SW faults in the southern part of the delta. The Cauvery river which has originally developed a broad bird-foot shaped – arcuate delta, has undergone a phase of anticlockwise rotational migration and stabilized in the northern rim of the delta as Coleroon river during 2300–750 Y.B.P. due to the ongoing tectonic emergence in the south of the delta almost since the last 6000 years or so. The Vellar river, in deltaic regime, shows northerly migration due to E–W grabening in the northern part of the delta. Vaigai and Manimuttar rivers are again migrating northerly in their deltaic regions due to the probable land arching to the south of their present day flow. Thus, the paper discusses the post deltaic / Middle -Late Holocene geological processes of Tamil Nadu deltas which are predominated by tectonic activities.

Abstract

Visualisation of geological process raises special issues for scientists and animators. The degree of physical movement of a rising arch or along a fault line may be very small compared to the normal terrain variation. Over a long time period the major changes in the environment may come from the more substantial surface manifestations of changing draining regimes. In Tamil Nadu State in South-Eastern India there are continuing tectonic movements arising from the collision of the subcontinent with the greater Asian land mass. Over comparatively recent times (7000 years) these movements have had a major impact on drainage and other hydrological outcomes. The Cauvery River in particular has migrated several hundred kilometers over this period. A mosaic was made from recent satellite imagery and then manipulated to create surface textures for dates between -7000 years and +1000 years. Changes in the terrain surface, such as rising arch structures and descending grabens, have been modelled and animated. The combination of terrain movement and surface change provides a visual history of the period.

Introduction

The continued northward movement (5±6 mm per year) of the subcontinental land mass of India induces substantial tectonic pressures all over India. In the southeast, primarily within Tamil Nadu, there is significant differential movement, both vertical and horizontal, of portions of the existing land mass. This is producing a number of effects:

Abstract

Drainages have characteristic pattern and life histories with youthful stage in hilly areas, mature stage in plains and old stage in the coastal zones. The deviations from their normal life histories, especially aberrations in their flow pattern in the form of various drainage anomalies have been inferred to be the indications of dominantly the Eustatic and Isostatic changes. This, especially after the advent of Earth Observing Satellites, has attracted the geoscientists from all over the world, for studying such drainage anomalies. In this connection, a study has been undertaken in parts of South India falling south of 14° south latitude to comprehensively map some drainage anomalies like deflected drainages, eyed drainages and compressed meanders and to evolve the tectonic scenario therefrom. The mapping of such mega drainage anomalies and the related lineaments/faults from the satellite digital data and the integration of such lineaments/faults with the overall lineament map of South India showed that the study area is marked by active N–S block faults and NE–SW sinistral and NW–SE dextral strike slip faults. Such an architecture of active tectonic grains indicates that the northerly directed compressive force which has originally drifted the Indian plate towards northerly is still active and deforming the Indian plate.

Introduction

Rivers have characteristic pattern and life histories with (1) short and straight drainages performing only erosion in the hilly catchments, (2) meandering and sinuous paths doing both erosion and deposition in the plains and (3) Brownian pattern of movement doing only dumping of sediments and building up of deltas in the coastal zones. Such characteristic life history of the rivers with youthful stage in the hills, mature stage in the plains and the old stage in the coastal zones in general are controlled by the base level of erosion or Mean Sea Level (Thornbury, 1985). But, the rock types and the geological structures of the terrain related to palaeo, time transgressive and ongoing tectonism too significantly control the drainage pattern and the related river flow dynamics in all these three stages. Hence, geoscientists from all over the world have all along been showing greater interest in understanding the drainage architecture in general and their anomalies in particular. That too, after the advent of Earth Observing Satellite technology, mapping of drainage pattern and their anomalies like dentritic, semi dentritic, trellis, parallel, annular, radial, deflected, pirated, avulted, eyed, compressed, preferentially migrated and other drainage anomalies have gained greater momentum, since, besides lithology, tectonics and sea level changes, these drainage anomalies have the credibility of providing information on the flood histories, seismic vulnerability, past climates and anthropogenic phenomenon too (Chitale, 1970; Chen and Stanley, 1995; Lillesand, 1989; Matmon et al., 1999; Miller, 1937; Reid, 1992; Saintot et al., 1999; Smith et al., 1997; Twidale, 2004; Thornbury, 1985 and many others). In different parts of the Indian sub-continent too, studies have been carried out on the drainage anomalies using topographic sheets, black and white panchromatic aerial photographs and orbital multimode and multispectral satellite data, to elucidate the structural fabric, tectonic processes, climatological and other phenomenon of especially the Quaternary period (Amalkar, 1988; Babu, 1975; Bakliwal and Sharma, 1980; Barooah and Bhattacharya, 1989; Mitra et al., 2005; Murty and Mishra, 1981; Narasimhan, 1990; Oldham et al., 1901; Philip et al., 1989; Rajaguru and Kale, 1985; Ramasamy, 1991, 2006; Ramasamy and Kumanan, 2000; Ramasamy et al., 1987, 1991, 2006; Singh et al., 1996; Sood et al., 1982; Thirunaranan, 1938; Vaidyanadhan, 1971; Yashpal et al., 1980).

Abstract

The Indian Peninsula in general and its southern part in particular has been thought to be a stable shield area and hence inert to younger earth movements and seismicities. However, in addition to fast relapsing seismicities, the studies carried out by earlier workers during the past three decades indicate possible pulsatory tectonism, at least since the Jurassics. The present study is a newer attempt to identify, analyse, and spatially amalgamate a large number of anomalies visibly displayed by the tectonic, fluvial, coastal, and hydrological systems in remote sensing and ground based datasets/observations, and to finally paint a fair picture on the active tectonic scenario of South India. The study reveals that the phenomena, viz. extensive soil erosion, reservoir siltation, sediment dump into the ocean, preferential migration of rivers, restricted marine regression, shrinkage of back waters, withdrawal of creeks, fall of groundwater table, etc., indicate two E–W trending ongoing tectonic (Cymatogenic) archings along Mangalore–Chennai in the north and Cochin–Ramanathapuram in the south. Intervening these two arches, a cymatogenic deep along Ponnani–Palghat–Manamelkudi exhibiting phenomena opposite to the above is observed. In addition, the characteristic tectonic, geomorphic, and hydrological anomalies observed in 1B satellite FCC data, as well as in the field, indicate N–S trending extensional, NE–SW sinistral, and NW–SE dextral strike slip faults. These anomalies and the tectonic features deduced there upon, indicate that the southern part of the Indian Peninsula is tectonically active due to the northerly to north– north-easterly directed compressive force related to post collision tectonics. This active tectonic model visualized for South India gives a further clue that the whole Indian plate is whirling like a worm with alternate E–W arching and deepening, along with block and transform faulting from Cape Comorin in the south to the Himalayas in the north.

Introduction

The Indian Peninsular Shield in general and its southern part in particular has always been thought of as being inert to younger earth movements and related seismicities / earthquakes. For this reason, geoscientists have not shown much interest in studying the Neo-active-seismotectonics of the southern part of the Indian Peninsula, mostly restricting themselves to the western (Kutch) and central (Son-Narmada) parts of India (Auden 1949, West 1962, Choubey 1970, Biswas and Deshpande 1973, Kailasam 1975, Ghosh 1976, Pal and Bhimashankaran 1976, Crawford 1978, Dessai and Peshwa 1978, Sharma 1978, Guha and Padale 1981, Kaila et al., 1981, 1985, Murty and Mishra 1981, Powar 1981, 1993, Bhagwandas and Patel 1984, Bakliwal and Ramasamy 1987, Merh 1987, Ravishankar 1987, Amalkar 1988, Ramasamy et al. 1991, Gupta 1992, Sareen et al. 1993, Ramasamy 1995a, 1998, and many others).

Abstract

The continental drifting and the movement of Indian plate to the tune of 6500 km in a time frame of 65 million years towards north north-easterly, its collision with Eurasian plate, the rise of mighty Himalayan mountains, the still prevalent northerly directed compressive force which has originally drifted the Indian plate and the disseminated intraplate seismicities have been the proven facts. In this context, a remote sensing based study carried out using IRS satellite images revealed that the whole Indian plate is whirling like a worm with series of alternately arranged E-W trending arches and deeps and N-S extensional/block faulting, NE-SW & NW-SE strike slip faults and E-W trending fracture swarms from Cape Comorin in the South to foot hills of Himalayas in the north. These ongoing tectonic activities have displayed hierarchy of geomorphic anomalies in the fluvial, coastal and hydrological systems and these suggest that the whole Indian subcontinent warrant detailed studies to understand the post drift kinematics and its impacts over the ecosystems, natural resources and natural disasters.

Introduction

Consequent to the continental drifting, the Indian plate has moved towards north northeasterly and collided with Eurasian plate, thus resulting into the rise of Mighty Himalayan Mountains along the junction of these two plate boundaries as demonstrated by many earlier Geoscientists. But the behaviour of the Indian plate, both during the collision and after that, has not been comprehensively studied and understood as to whether it has remained as an inert plate or suffered any mid plate deformations. However, disseminated information has been brought out by many earlier workers on the post trappean arches, deeps, horsts and grabens within the

Indian plate. Some of such tectonic grains from north to south in the Indian Peninsular are:

Abstract

Historically, the tiny island katchatheevu located in between Rameshwaram and Srilanka belongs to Ramnad Kingdom and it was handed over to Britishers and during the British’s rule. During that time both Indian and Srilankan fishermen communities were using this for their fishing related activities. On a goodwill, in 1994, the Government of India donated this island to Srilanka. Since then it has become a major issue and a perpetual problem to Indian fishermen that they could neither do fishing around nor berth their boats for drying their fishing nets. Under this scenario, an attempt was made to evaluate the geological setting of Katchatheevu island using E-Topo data which provides the sea bottom topography/morphology. The study revealed that the Katchatheevu island is the north eastern extension of the Pisasumunai of the Rameshwaram island and such arcuate nature of the land between the Pisasumunai and Katchatheevu is attributed to anticlockwisly spiralling littoral currents which would have dumped the sands and developed the island. Thus the study brings some newer information that the Katchatheevu is geologically a part of Indian land mass.

Studies and Findings

The boundary problems within the nations and amongst the nations, especially amongst the territorial nations, have started emerging as major issues of global concern. Katchatheevu Theevu located between India and Sri Lanka is one such a major issue, as the said island which originally belonged to Ramnad kingdom was handed over to Sri Lanka by India in 1974 and since then, the Indian fishermen community is facing untold miseries in the hands of Sri Lankans and hence it warrents immediate attention.

Abstract

The Adam bridge, the curvilinear chains of islands linking India (Thanushkodi) with Sri Lanka (Thalaimannar), has been a matter of scientific and mythological debate. While the great epic Ramayana says that Lord Rama built this Adam bridge around 1.5 million years ago to bring back his wife Seetha from Srilanka who was a captive by king Ravana of Srilanka, some reports gave another view that it is coral islands of 1.7 million years of age. Under this backdrop, the author refutes the claim made by NASA that the Adam bridge was located firstly by one of its satellites and cited evidences that the Indian scientists located and mapped it using the IRS satellite data much earlier. Further, on the basis of bundles of beach ridges dated in Tiruthuraipoondi-Vedaranniyam area and as well as some of these continue up to Uchipulli area in Ramanathpuram district, the author assigned an age of 3500 YBP ( Years Before Present) to Uchipulli beach ridges seen in the main land to the west of Rameshwaram and Adam’s bridge and inferred that the Adam’s bridge must be equal to or younger than 3500 YBP. The easterly nosing of Indian mainland in Ramanathapuram – Rameshwaram – Thanushkodi and its further extension in the form of Adam bridge, the author demonstrated that the because of anticlockwisely rotating littoral currents to the north and clockwisely moving littoral currents to the south of Adam bridge, the chains sandy islands namely Adam’s bridge was formed by the segregation of sands in between currents shadow zone after 3500 YBP.

Studies and Findings

There was some coverage in the newspapers some time ago about the discovery of a land bridge (Adam’s Bridge) between Dhanushkodi (India) and Talaimannar (Sri Lanka) by NASA through one of its satellite mission. It was also written in some articles that this land bridge was constructed by Lord Rama 1.7 million years ago to reach Sri Lanka with the aim to bring back his wife Sita from the clutches of Ravana. However, this linkage was refuted by NASA. It accepted that the picture was captured by one of its satellites, but it was unaware of the linkage of the land bridge with the great Indian epic Ramayana. Some reports gave another view and mentioned that the bridge was nothing, but 1.7 million years old coral reefs. Many historians have also come out against linking the Adam’s Bridge with Ramayana.

Abstract

The time-transgressive changes in the landscape architecture of the Rameswaram island located in the semiarid tract of southeastern India, was animated using ARC/INFO GIS. The animation has shown that the Rameswaram island has evolved through an interplay of tectonic. fluvial, marine and aeolian activities and that the Aeolian activity was accentuated during 1921-1990 A.D

Introduction

The state of Tamil Nadu in the southeastern fringe of India has well evolved riverine ecosystem in the east and a 900 km. long coastal ecosytem in the eastern fringe. From Vedaranniyam in the northeast to Cape Comorin in the southwest these fluvial and coastal ecosystems show evidence of Aeolian activity, especially during the Holocene. Several researches1, 2, 3, 4,5, 6, 7, 8, 9, 10, 11, 12, 13,14, 15, 16, 17, 18, 19 have studied the Quaternary tectonic, fluvial, fluviomarine and marine processes in this part of the semi-arid tract.

Abstract

The coastal zones are very fragile owing to the reason that these form the junction between the continents and the oceans. Further the multivariate tectonic, fluvial, marine and aeolian processes, which vary independently in their degrees and duration in space and time, act in different permutations and combinations with each other and keep on constructing and destroying the landforms along the coasts. Again, as coastal zones are heavily populated; it adds further pressure on the coastal systems. The paper deals about the hierarchy of issues faced by the coastal zones like tectonic emergence and subsidence and it‘s impacts and the ways, means and needs for measuring the rate of such movements; marine regression and the need for the time series models on the land-ocean boundaries for drawing the sea level curve for India, the Quaternary deltas and the essentiality for understanding the mixture of fluvial and marine forces for the possible future forecasting models; back water modifications, the related issues and the demands for the sediment-chemo dynamics modelling; disaster vulnerabilities and mapping methodologies etc; all using the unexplored vistas of Geomatics technology. The concept has been explained by taking Tamilnadu coast as the reference region.

Introduction

The coastal zones are always fragile as these are formed by the tectonic, fluvial, marine and aeolian processes, which act independently in varying degrees and duration and occur cumulatively in different permutations and combinations along the different parts of the coasts. In addition to such inherent fragility, the coastal zones stand vulnerably exposed to various natural and anthropogenic disasters like seismicity and earth movements, tsunamis, floods, sea level rise, cyclones, coastal erosion etc. Further, owing to the enriched land and water resources, enjoyable eco systems and avenues for intra and intercontinental trades, more than 70% of the global population and the related infrastructure are clustered in the coastal zones. Hence the scientists from all over the world have started showing more attention towards the coastal regions (Ahmed, 1972). The advent of Geomatics technology comprising multi spectral and hyper spectral remote sensing, GIS, GPS, Interferometry, etc. have opened up exhaustive newer vistas in unfurling the hidden complexities of the coastal zones and to provide solutions. From amongst many, the remote sensing based studies carried out by Shailesh Nayak and his team (2004) have brought out many first time information to light about the Indian coasts. But still we will have to go a long way, as the global coasts in general and the Indian coasts in particular are confronted with a hierarchy of challenges and the Geomatics technology can provide answers for these challenging issues owing to its unique virtues. The paper narrates the unique issues of the Indian coasts and how effectively the geomatics technology can be used in solving them. This has been done by taking Tamil Nadu coast as the test area.

Abstract

Geomorphology not only provides the panorama on the external architecture of the Earth surface, but also it is the record of the past geological events including the climate, especially of the Quaternary period. Detailed geomorphology map was prepared using the IRS LISS IV FCC and SRTM data showing the tectonic, denudational and fluvial landforms of Kollai hill, Eastern Ghats, Tamil Nadu. The geomorphic features showed that the Kollai hill can be divided into two as northern and southern blocks separated by a NE-SW active sinistral fault in the overall N-S rectangular hill. The integration all the geological , structural and geomorphic features show that the Kolli hill is under the grip of uplift in the south west with hinge towards north easterly. Because of this, the northern block/rim of the hill is fragmented into a series of East-West trending fracture/ fault swarms which are sympathetic tectonic grains to the Attur graben rimming the Kollai hill to its north. This phenomenon seems to control the overall resources and environment of the hill.

Introduction

The mountains are not only the store houses of natural resources like minerals, water, geothermal springs, forest & biomass etc., but also possesses unique & self-styled ecosystems drafting the mankind from the plains for comfort and livelihood. Further, the tourists are highly attracted by the mountain regions due to the ecosystems, climate and scenic beauty. Due to all these, the resources of the mountains are exponentially exploited during the recent 6–7 decades thus causing phenomenal depletion of natural resources and initiation of chains of environmental disorders, viz., deforestation triggered soil erosion, landslides, debris dumping along the slopes and foot hills, sedimentation of the downhill reservoirs & drainages, all of which in turn induce haphazard flooding. Hence, the Union and various Federal Governments have started working on the restoration of the ecosystems of their respective mountain regions in several nations. In the Indian sub- continent too, both under the Centrally sponsored schemes and the State funding, number of Hill Area Development Programmes have been initiated and going on especially in Himalayas, Easternghats and Westernghats. The state of Tamil Nadu possesses both Easternghats and Westernghats. While the Westernghats are found along the western part of the state with NNW-SSE orientation, the Easternghats represented by the Kollai- Pachhamalai hills, Shevroy - Chitteri – Kalrayan hills and Javadi hills, aligned in N-S direction, are traversing the Central part of Tamil Nadu. To comprehensively understand the resources, hazards potential, the ecosystems and also the modern geological processes which only control and tutor them, a geomatics based study was carried out in Kollai hills so that it can be used as a reference study to all those who are engaged in eco-restoration and hill area development programmes in India.

Abstract

From amongst various geomorphic features the landforms generated by the river systems are significant as these are not only the records of the life histories of the rivers, but also the various dynamic processes and phenomenon operated during their origin like tectonic movements, sea level changes, flood histories, climate changes etc. In this connection a study has been conducted using the satellite borne multi spectral remote sensing data in mapping the flood plains, particularly their anomalies like symmetrical, asymmetrical, multilevel, offset and meander scrolled flood plains of some selected rivers from Asia viz: Tamirabharani, Cauvery and Brahmaputra from India, Indus river from Pakisthan and Tineg river from Phillipines. The paper discusses about these and their significance in unfurling the ongoing tectonic movements, sea level changes, palaeo – ongoing strom surge / tidal activities, ongoing earth tremors etc.

Introduction

The Rivers are not simply the carriers of water from the mountain ranges to the plains and to the oceans. But they have well defined and characteristic life histories of their own, with youthful stage in the mountains, mature stage in the plains and the old stage in the coastal regions [6] and the life histories of the rivers are often compared with man’s life. Infact, once the rivers are born on the surface of the Earth, their only aim is to attain the Mean Sea Level (MSL) or the base level of erosion as early as possible and as short as possible. So, in the mountains, which are normally their regions of origin, since the rivers occur thousands of meters above the MSL, flow vibrantly taking advantage of the slope as short and straight drainages to cut deeply the terrain so as to attain the MSL easily. Since such vibrant activities of the rivers, appear to be similar to the human youths, the rivers are said to be in youthful stage in the mountain regions and the erosion is the only dominant activity. But, on climbing down the hills and reaching the plains, as they still occur at hundreds of meters above the MSL, continue to flow towards the sea but with meandering, sinuous and oscillatory paths as they have lost their elevations when compared to the mountains and in this process of meandering perform both erosion and deposition. As such stabilized flow or “Watch and walk phase” of the rivers in the plains resembles the matured behavior of the middle aged Men, it is called as mature stage of the rivers. In contrast, when the rivers reach the coastal zones as they have attained the MSL, they don’t have any energy to carry even their own load and hence dump all the sediments as deltas, oscillate here and there and finally somehow reach the sea. Such Brownian movement of the rivers as replicates the activities of the old Men, called as the old stage of the rivers. Thus the erosion, both erosion and deposition and only the deposition are respectively the activities of the rivers in these three stages, accordingly the respective and contrasting landforms are formed in these three different stages of the rivers.

Abstract

The dating of fluvial landforms by archaeological, epigraphical, historical, thermo-luminescence, radiocarbon, etc. are of greater significance because it not only provides information on the date of origin of such fluvial landforms but also isostatic, eustatic, climatic histories of the Quaternary period. Hence, the Geoscientists have always been giving greater importance to the dating of the fluvial landforms. In India, the Cauvery is one such river studied for its migratory melodrama with the help of satellite data and inferred that the river Cauvery has earlier flowed along the Hogenekkal-Chennai tract (PCS-1-Palaeo Channel System-1) during 500 thousand to 3000 YBP (years Before Present), then migrated towards southerly and flowed along the present day paths of Thoppurar, Vaniyar and Ponnaiyar rivers (PCS-2) during 2700-2300 YBP and further migrated southerly and entered into Tiruchirappalli-Thanjavur plains after 2300 YBP and finally anticlockwisely migrated in different parts of the present day Cauvery delta and stabilized as river Coleroon during 2100-750 YBP. Such broad chronological history was brought out on the basis of archaeological, epigraphical, historical, literature and few radiocarbon dating. In the present study, more number of radiocarbon dating was done in various palaeochannels of river Cauvery which has over all coincided with above observations and further provided discrete information on (1) the southerly migration of river Cauvery from PCS-1 to PCS-2 after 8000 YBP, (2) tectonic arching and splitting up of channels in Chennai region during above period, (3) gradual younging nature of palaeochannels from PCS-1 of Chennai region to PCS-3 of Tiruchirappalli – Thanjavur region, etc.

8.1 Economic Geology and Ore Mineralogy

8.1.1 Economic geology

Economic Geology deals with the comprehensive study of mineral deposits including their processes of formation and uses. By applying the principles of geology, a mining engineer is able to exploit such deposits profitably for the use of Man.

8.1.2 Ore mineral

An ore is a term applied usually to that part of a metalliferous mineral deposit that can be utilized profitably as a source of one-or-more metals, this term now is widely used for the usable part of many non-metallic (non-metalliferous mineral) deposits, like barite, fluorite, sulphur, etc.

8.1.3 Gangue mineral

An ore is usually a mixture of one or more usable minerals (ore minerals) and one or more unusable minerals (gangue minerals). The usual gangue minerals are quartz and other forms of silica, calcite, dolomite, siderite, barite, feldspars, garnet, chlorite, kaolin, fluorite, apatite, pyrite, pyrrhotite, arsenopyrite, and sometimes the gangue material is the country rock or host rock itself in which the ore minerals occur. Sometimes, the gangue minerals may also be utilized as by-products of the ore deposit. The nature and proportion of the gangue influence the economic value of an ore to a great extent.

7.1 Introduction

The earth's crust is made up of igneous, sedimentary and metamorphic rocks. Each variety of rocks exhibit some columnar joints in Igneous rock, characteristic structures like bedding in sedimentary rocks and fabrics like schistosity and gneissosity in metamorphic rocks.

As a result of tectonic activities in nature, rocks may suffer deformation, rupture, dislocation of beds (Fault) or other planar structures.. The whole study of such deformation is known as structural Geology. It has been observed that sedimentary rocks are most suitable for studying structures, because these rocks are deposited in quiet environment, and initially the beds arranged in horizontal position. As a result of stress due to kinematic movements/tectonism, the horizontal beds tend to deviate from their horizontal disposition to dipping position or get folded or faulted. Thus the rock develops various kinds of structures. There are following structures present in sedimentary rocks: