eChapters

The resources on the land have started showing sign of faster depletion owing to the population explosion, over exploitation of mineral and water resources and also the improper exploitation and the related wasting of the natural resources. Hence a time has come to search for more and more newer natural resources amongst which the ocean resources gain supreme importance as this treasure is yet to be hunted due to the non - availability of suitable technology for the same.

Such ocean resources mainly include the mineralogical and biological resources. The ocean biological resources, their birth, growth, population and migration greatly depend as chlorophyll content, total dissolved oxygen, total suspended solids, salinity etc. These parameters which constitute the marine environment drastically change in a quick span of time owing to the dynamically changing marine forces.

Abstract

The present study has revealed that the NE-SW and WNW-ESE trending sinistral faults are very active along the Tamil Nadu coast and the same have caused considerable slope modifications along the Coleroon and Karungalar rivers which are well-manifested in the land, water and mudflat distribution pattern. Similarly, the progradation of the land in Vedaranniam nose is due to the rise of Pattukottai-Mannargudi area and the time transgressive modifications of the Vedaranniam backwater indicates the opening up of the N-S trending Pleistocene-Holocene faults.

Abstract

The art of remote sensing has opened up many vistas in the study of river migration as satellite photographs, both in their normal and digitally enhanced modes, vividly show the rivers and their migratory signatures. The rivers migrate for various reasons amongst which tectonic movement is one of the main causes. In the present study an attempt has been made to exhibit the palaeochannel network of the rivers of Western India and integrate them with lineament fabric, so as to understand the Quaternary tectonics of the region. The study has shown that Western India shows considerable signs of Quaternary tectonics.

The great Indian epic ‘Ramayana’ says that ‘Lord Rama’ has tried to cross over the Bay of Bengal so as to reach Sri Lanka from India from three points along the southeastern fringe of the Indian coast. Firstly, he is said to have tried to cross from Vedaranniyam which is mythologically called as ‘Kodiyakkarai’ Secondly from Manamelkudi and finally crossed over to Sri Lanka from Rameswaram Island (Fig.1), as the former two coastal locations were widely separated from Sri Lanka by Bay of Bengal and the Rameswaram Island was nearer to Sri Lanka during that period. But, the recently acquired satellite data shows the huge accretion of sediments and rapid land building activity off Vedaranniyam coast (Fig. 2 and 3). The geomorphic interpretations carried out using IRS 1A imagery and 14^C archaeological dating of such geomorphic features have shown that such ongoing sediment accretion phenomena off vedaranniyam nose might in future connect the Vedaranniyam part of Indian Peninsula with Jaffna Peninsula of Sri Lanka if the sediment accumulation continues unabated. The sediment accretion in this area, therefore, requires detailed studies particularly in the context of the coastal ecosystem (Fig. 1).

Abstract

The Remote Sensing and the followed up field based investigations show that the Tamil Nadu coast, India, is facing series of geoenvironmental problems due to tectonic movements and morphodynamic processes. Such problems pose a challenge to the engineering geologists. The paper discusses such challenging engineering geological problems and plausible remedial measures.

Abstract

The tectonic and the geomorphic features observed along the west coast of the area between Mangalore and Cape Comorin show that the NNW-SSE trending west coast has been carved out by the Western Ghats orogeny and the related NNW-SSE trending release fractures. The sinuosity of the otherwise straight coast line is due to Quaternary cymatogenic arching caused by the thrust related to the northerly movement of the Indian plate. The coast line has further attained peaks, projections and serrations due to the ENE-WSW trending series of Precambrian extension fractures which were reactivated gaining the northeasterly directed forces from the rising Carlsberg ridge. Overall, the west coast is being tectonically evolved even today due to the rise of Carlsberg ridge and the Indian plate movement.

Abstract

There is a consensus amongst the geoscientists that overall there has been progradation along the east and west coasts of peninsular India. However, the present day configuration of the coasts and some of the geomorphologic features such as absence of spit and delta along west coast and absence of major estuaries and petroliferous structures along east coast still remain controversial. The present study, based on the appreciation of certain geomorphological and tectonic features on Landsat imagery and aerial photographs of southern part of Indian Peninsula, suggests that the evolution of the coastline has been mainly controlled by tectonism.

The tapering nature of the coastline is attributed to the Precambrian orographic axis. The serrated nature of the post Precambrian coast line is due to the Precambrian transverse faults, whereas the serrated margin of the post Gondwana, Post cretaceous and post Tertiary coast lines are attributed once again to the Precambrian faults reactivated time and again. During the Quaternary period the coast line has undergone many modifications. The coast line attained sinuosity due to Pleistocene folding which is well manifested by river migration. The coast line was subsequently faulted and shifted with en echelon pattern due to N-S regional compression which is referable to the collision of Indian Plate with Tibetan plate.

Remote sensing has proved its credibility beyond doubt in natural resources survey and environmental monitoring owing to its synoptivity, multispectral photographic capability and repetitive coverage. While its synoptivity gives unbiased information on the regional panorama of the earth surface, its multispectral possibility aids precise interpretation of various objects, as different terrestrial objects exhibit various spectral responses in different bands of the electromagnetic spectrum. Amongst various terrestrial objects, water has a characteristic spectral response of its own, i.e. it permits the blue / red part of EMR (electromagnetic radiation, 0.4-0.8 µm) to penetrate inside. On the contrary, it totally absorbs the infrared part of EMR (0.8-1.5 µm). As such blue/red part of EMR penetrates the water bodies, the impurities and suspended sediments are seen very clearly in various shades of gray as and when the water bodies are shallow. Many workers, therefore, have used blue / red band of the satellite data in such water-quality studies^l-3. Hardy⁴ has observed that the infrared light in the spectral regions of 0.6-1.4 µm has the potential to map the turbidity in the ocean water, whereas Kritakos et al ⁵ have used the rationed data of visible and near infrared bands (0.4-1.1 µm) and obtained better results for water quality monitoring. Keeping such facts in mind, the blue/red band (band 2) of the IRS 1A satellite data was used to configurate the bathymetry along Madras coast in Bay of Bengal (Figure 1 a).

In the present study, the IRS lA band 2 data (0.52-0.59 µm) of March 1991 was used and subjected to edge enhancement studies for the coastal zone of Madras (Figure 1 a). Such edge enhancement normally sharpens the edges of two contrasting objects or sharpens the edges of objects of contrasting relief. In such edge enhanced data, few

Abstract

The East Coast of Tamil Nadu exhibits a spectacular network of deltas formed by the easterly flowing river systems. The study of raw and digitally enhanced Landsat TM and IRS data shows, that these deltas were formed due to multivariate dynamic processes of fluvial, marine and aeolian actions. The wide fan shaped delta observed northwest and north of Madras city spanning out over an area of 700 sq.km is a feature, standing testimony to the PaleoCauvery river systems.

The regional slope and the overall arcuate arrangement of the crescent shaped lakes in the area and the tentacles of paleochannels show, that it is overall a fan shaped delta and its successive growth towards the sea might have been due to the constant progradation of lobes by continuous reworking of preceding lobes. The depressions in between successive concentric lobes have become the lakes. The absence of any beach ridges in such palaeo deltaic regime suggests that, it would be a sub aerial delta only. The overall arcuate shape of the shoreline in between Madras city in the south and Pulicat lake in the north is due to this fan delta. This feature once again symbolises the active river dominated delta. The Palar delta is a ‘cuspate’ one. The Ponnaiyar river has developed a linear delta, along a narrow depression found in between Tertiary uplands. While the avulsion phenomenon indicates the ancient shoreline near Villupuram, the east-west trending micro sandy uplands within the delta suggest, that it is a tide dominated delta.

Abstract

Satellite photographs depict exciting evidence on the migratory melodrama of river systems. A study has been conduced in parts of Tamil Nadu using IRS-IA Satellite pictures, archaeology and Tamil literature, which reveals that from Pleistocene to 2700 years B.P.(Before Present) the river Cauvery flowed in a northeasterly direction from the Stanley reservoir via Chinnar, Palakkodu, Mattur, Tiruppathur (Tiruppattur), Gudiyatham (Gudiyattam), Vellore and Walajapet to meet the sea at Madras. From 2700 to 2300 years B.P., it flowed via Uttangarai and Tirukkovilur to meet the bay of Bengal near Pondicherry, over which the present-day Ponnaiyar is a misfit stream . From 2300 to 1300 year B.P. it has flowed via Erode, Tirukkampuliyur, Alagarai , Tiruchy, Kiranur and Pudukkottai meeting the sea in the region where the present-day Agniar and Ambuliar meet the sea. Subsequently, between 1600 and 1300 years B.P., the Cauvery flowed along the present-day tracts of the Vennar and Vettar, after which it seems to have flowed as the Kodamurutti, Arasalar and PalanCauvery from 1300 to 1000 years B.P. From about 900 years B.P. it flowed via Tirupurampayam (Tirupurambiyam), Achalpuram till around 750 years B.P. and then it is stabilised as the Colleroon (Kollidam). Such periods and phases of river migration as well as their implications in the search for archaeological remains are discussed in this paper.

Much has been talked about the mighty river systems and their migratory histories, since Purana and Vedic times. In Mahabharata the places where the Lord Krishna is said to have played with Gopis in the banks of River Yamuna are now forming flat lands many kilometers away from the present day Yamuna. In the same way, there is a mention in ancient literature about the ‘Indo-Brahm’ river which was originated from the Himalayas and flown through Brahmaputra valley, Indo-Gangetic plains, Rajasthan desert and met the Arabian Sea in Rann of Kutch. Such a mighty river is said to have fragmented into Brahmaputra, Ganges and the Indus rivers due to Tectonic activity in Himalayan regions. Similarly there are many evidences in the Tamil literature. For example in ‘Kalingathuparani’ it is mentioned that the river ‘Palar’ was flowing north of Kanchipuram but the same river is now flowing south of it.

All these facts show that the rivers have the tendency to frequently change their courses. The advent of modern Remote Sensing Technology has opened up new vistas in studying such migratory rhythms of the rivers, as such old and buried rivers exhibit spectacular ribbon like, linear, curvilinear and contorted features with typical darker tone in black and white images and reddish tone in false color composites (FCC) and other color coded images.

Abstract

The art of remote sensing has opened up many vistas in the study of river migration as satellite photographs, both in their normal and digitally enhanced modes, vividly show the rivers and their migratory signatures. The rivers migrate for various reasons amongst which tectonic movement is one of the main causes. In the present study an attempt has been made to exhibit the palaeochannel network of the rivers of Western India and integrate them with lineament fabric, so as to understand the Quaternary tectonics of the region. The study has shown that Western India shows considerable signs of Quaternary tectonics.

Abstract

The anomalies observed in the reverine systems have been demonstrated to be the potential tool in deciphering the tectonically active zones. Such various drainage anomalies viz: radial drainages, anomalous compressed meanders, eyed drainage and the youthful floodplains observed in Annamali – Palani - Varushanad hill ranges of the Western Ghats of Tamil Nadu show that the N-S and NE-SW trending faults are tectonically active in the recent years.

Abstract

It has been established beyond doubt that the drainage architecture and the fluvial histories of river systems give excellent indications not only on the surficial lithology but also on the ongoing morphotectonic processes of the planet earth. Among the various drainage patterns, the ‘eyed drainage’ pattern is considered to be one of the most significant anomalies and such ‘mega eyed’ drainages interpreted from IRS-IA imagery in some of the major river systems in Tamil Nadu, Indian Peninsula, are found to signify ongoing tectonic movements in an otherwise seismically inert shield area.

Abstract

Satellite imagery interpretation has shown the existence of a major Palaeochannel system in the Great Indian desert. These palaeochannels belong to the mythological Sarasvati river, which seems to have flowed southwesterly close to the Aravalli hill ranges and joined the sea in the Great Rann of Kutch. Subsequently it seems to have shifted northwesterly, and more precisely in an anti-clockwise direction and got buried in the desert in Anupgarh plains. While its oldest course is the now misfit Luni river, its final trace is now represented by Ghaggar river. Whereas its overall northwesterly migration is attributed to NE-SW trending cymatogenic arching along the Great Rann of Kutch in the southwest to the Siwalik hills in the northeast, its multivariate palaeodrainage is attributed to block faulting and land subsidence in the Bikaner sector.

Abstract

The recent earth movements and the related seismicities in the Southern part of the Indian Peninsula has been a matter of enigma for a century and more. While one school was strongly holding the opinion that the southern Indian Peninsula is free from recent earth movements as it is a shield area, the other school has narrated the possibilities for the ongoing earth movements. Under these circumstances, the various anomalies observed from satellite data and ground based information on geomorphology, subsurface lithology, geophysics, hydrogeology, geochemistry etc. have suggested a possible Pleistocene / Holocene graben along Pondicherry in the northeast and Cumbum Valley in the southwest in the southern tip of the Indian Peninsula.

The geologists of the Indian subcontinent have all along been of the opinion, that, the southern part of the Indian Peninsula is a stable shield area. But, the recently acquired IRS-1A image of June, 1988 vividly displays spectacular geomorphic anomalies suggesting that this part of the Indian subcontinent is prone to earth movements. In order to unearth more evidences on such earth movements / neotectonism in Tamil Nadu, the IRS-1A image of Coromandel coast of Tamil Nadu was analysed ( Fig. 1).

OBSERVATIONS

• The IRS-1A image conspicuously displays three contrasting morphotectonic domains in the study area marked by the western undissected Tertiary upland (Vallam upland), central highly dissected Tertiary upland (Pattukottai -Mannargudi upland) and the eastern Cauvery delta (Fig 1 and 2). These three domains are separated by two conspicuous N-S trending lineaments (E and F, Fig.1 and 2) namely the Tanjavur - Avadaiyarkovil lineament in the west and Kumbakonam -Muttupet lineament in the east.
• In addition, two more E-W trending lineaments (G and H, Fig.1 and 2) are also observed trifurcating the undissected Vallam upland into three blocks.
• Along these lineaments, especially the Tanjavur -Avadaiyarkovil and Kumbakonam -Muttupet lineaments, the rivers show conspicuous drainage anomalies in the form of drainage deflection, drainage compression etc., wherever they transect the lineaments.

Abstract

The southern part of the Indian Peninsula has long been regarded as a stable area free from Pleistocene tectonics as it represents the Precambrian shield region. But the frequent earth tremors even up to a magnitude of 6.5 (Richter scale) which occurred in Tamil Nadu have started encouraging the geologists to think that it could possibly be a seismic prone zone. In addition, images acquired by the polar orbiting satellites offered valuable information on the fracture systems and fluvial anomalies suggesting possible Pleistocene tectonism in South India. Hence, a study has been undertaken to evaluate the signatures of Pleistocene tectonism in South India using IRS-lA, LISS-1 FCC imagery (Indian Remote Sensing Satellite lA, Linear Imaging Self Scanning 1, False Colour Composite) involving band 2, 3 and 4 under blue, green and red bands respectively.

The study has brought out a series of E-W trending cymatogenic arches and N-S trending extension, NE-SW trending sinistral, NW-SE trending dextral and E-W trending release fractures with characteristic signatures supporting Pleistocene tectonism in Tamil Nadu and Kerala.

On the basis of such morphotectonic features, a Pleistocene tectonic model has been presented with a N-S trending greatest principal stress and an E-W oriented least principal stress related to the movement of the Indian plate towards the Tibetan plate. Based on the model developed for Tamil Nadu and Kerala, a series of E-W trending cymatogenic arches and deeps have been proposed for Cochin- Rameswaram in the south to the Himalayas in the north. Further studies for seismotectonics, geothermal resources and hydrocarbon search have also been suggested along such arches and deeps.

Abstract

The tectonics of the geological past from Archaeozoic to early part of Cenozoic era has been studied due to their penetrative documentation in the form of folds and faults. But the tectonic history of the latter part of the Cenozoic era (i.e Pleistocene period) has remained a matter of conjecture owing to the poor response of the rocks to Pleistocene movements. In the present study the authors presented a model for the Pleistocene earth movements of South India through the study of river migration, coast line changes and lineament fabric derived from the space borne photographs.

In the area of study, the northerly migration of Paleru and Pennar and southerly shift of Palar, Ponnaiyar and Cauvery rivers, marine regressions restricted within this segment and the closely spaced crest line fractures suggest a lineament controlled E-W trending Quaternary upwarping along Mangalore-Madras alignment. Similar E-W cymatogeny is inferred in the southern tip of the Peninsular India on the basis of once again such observations. Such E-W trending Pleistocene arching phenomenon suggests a N-S oriented regional compression which could be related to the collision of Indian plate with Tibetan plate.

Abstract

Subsequent to December 26^th 2004 historical Tsunami, The Government of India has conceived a master plan for setting up Tsunami Warning System (TWS) similar to Pacific Ocean Tsunami Warning System. Concurrently, the union Govt has also initiated scientific studies through Department of Science and Technology and the significant amongst these are the

• All India Co-ordinated Programme on Tsunami disaster and risk assessment using GIS technology and
• Bilateral programme with Norway to know the know – how and capacity building in the fields of Landslides and Tsunami

As a part of this bilateral mission, the authors visited institutions connected to Geohazards and Tsunami affected areas of Norway. The article briefly narrates the salient inferences on the Tsunami scenario and the related studies in Norway.

Keywords: Landslides triggered tsunamis, Norway