eChapters

ABSTRACT

Worldwide reinterpretation of evolutionary history of sedimentary basins had commenced with the introduction of sequence stratigraphic concepts by geoscientists of Exxon. The eustatic sea level controlled deposition in sedimentary basins together with synchronous excursions of many trace elemental and stable isotopic compositions of sedimentary strata have led to a proposition that geographically widely separated sedimentary strata could be classified and correlated with ease by application of sequence stratigraphy and chemostratigraphy, relatively younger branches. This paper reviews the key definitions of these stratigraphic methods, presents an overview on their applicability in petroleum exploration, reservoir characterization and stratigraphic correlation. Considering the man-hours required for interpretation of sequences and chemozones from large quantum of core samples being generated from exploration activities and the possibility of human-error and biased nature of interpretations, an automation scheme involving statistical discrimination is suggested. The statistical discrimination method has been tested to have 76-100 % distinction of depositional units of Recent – Cretaceous in age in terms of sequences, chemozones, lithostratigraphic units, petrographic types and sedimentary microenvironments with 100% reproducibility of predictions. Hence, creation of a large database with well constrained subpopulations and putting it to use for recognition of depositional units and correlation of strata and reservoir characterization is suggested which may reduce operational inconsistencies and improve exploration strategies.

ABSTRACT

The carbonatites are genetically and geochemically distinct and contain several rare earth minerals that are unknown or are very rare in other types of rocks. A useful review of the REE’s in carbonatites is given by Cullers and Graf (1984), who point out that carbonatite contains the highest concentration of REE’s and highest LREE: HREE (La:Lu) ratio of any igneous rock. High REE abundances are considered as the diagnostic character of carbonatites to discriminate them against recrystallized limestone. Rare earth mineralization in carbonatities can be classified into three categories. The first is primary magmatic crystallization (bastnaesite). The second is hydrothermal mineralization and the third is supergene mineralization produced by weathering of carbonatitie bodies. The only economic Nb mineral in carbonatite is pyrochlore. Apatite deposits constitute the largest bulk mining in carbonatites and have higher phosphate content than marine phosphorites. Pyrochlore, cubic fergusonite, eschynite, Fe-Nb rutile, monazite apatite, bastnaesite and allanite are the rare earth minerals that are enriched in Tamil Nadu carbonatites. Such enrichment of above rare earths is typical of undersaturated alkaline complexes. The lanthanides are seen associated with these minerals, mainly the light lanthanides are predominant than heavier ones. Thus the carbonatite complexes provide the locus for several metal deposits that are presently of strategic importance, containing elements, which are otherwise largely dispersed in earth crust.

ABSTRACT

The multi-sensor airborne geophysical survey was carried out over Nalgonda district, Andhra Pradesh, during the field season 2002-03, with an objective to locate potential areas for mineral exploration. The area comprises older metamorphic rocks of Peninsular Gneissic Complex of Archaeanage represented by gneisses, granite, amphibolite and banded magnetite quartzite. Leucocratic intrusive granite, extending over a length of about 40 km around Suryapet in NNW-SSE direction exhibits intense fracturing. Two sets of vertical to sub-vertical fractures have been noted in granite. Yellow stains observed in granite near fracture planes reveal the presence of secondary radioactive mineral encrustation. The ground magnetic and spectrometric observations indicated that the uranium mineralization is confined to these fractures in granite. Petrographic, ore-microscopic and scanning electron microscopic studies revealed evidences of metamict alteration surrounding monazite/apatite inclusions within biotite, and magnetite grains in granite. These studies also indicated evidences of discrete grains of uraninite / coffenite / pitchblende (containing Thand Ce). Chemical analysis of the rock samples (by NAA) collected from anomalous zone reveal high uranium concentration of the order of 1200 ppm, marked by high values of total Rare Earth Element concentration (800 ppm).

The leucogranites are characterized by high LREE and a negative Eu anomaly suggesting plagioclase fractionation. An ultramafic enclave near village Kutubsahipur shows highest concentration of both uranium (1240 ppm) and REE (890 ppm) analyzed by BARC and NAA Lab, GSI.

Abstract

The landslides that swallowed the whole of Malin village, Maharashtra on the early morning hours of 30 July, 2014 is one of the major disasters, next only to Kedarnath episode in the recent years. Consequently, the Department of Science and Technology, New Delhi, constituted an expert committee comprising the authors of the article which made a visit and took the on the spot assessment of the disaster. Their observations show that the area is covered by the Deccan basalts, which are layered with compact and vesicular basalts; fractured and jointed basalts due to tectonics and the cooling of the basalts; and have also undergone extensive geomorphic evolution. Due to such geologic/geomorphic setting, the flow layered basaltic hillock in which Malin is located is naturally benched, which is further being leveled for the agriculture purposes. The deforestation, leveling of the hills, excessive usage of water for irrigation and the lack of drainages outlet in such benched and leveled slopes have assigned high degree of landslide vulnerability to the area. Over this, when torrential rainfall occurred in the last week of July, the landslide was triggered. On the basis such inferences, some mitigation measures have been evolved after the visit.

Abstract

The landslide vulnerability of the state of Mizoram is already high due to lithology, structure, geomorphology and seismotectonics and also the rainfall, like the other states of the northeastern region of India. The extensive mining activities along the highways for the building and road materials appear to cause additional problems of landslides. So two prominent landslides occurring in Keifang and Tlungvel quarries,Mizoram were studied. Besides taking stock of the geosystems, boreholes were drilled in both slides and from the total depth drilled and the modified core recovery, the RQD were worked out for the rocks which indicates that geotechnically the rocks of Keifang quarry are weak when compared to Tlungvel quarry. The geophysical surveys too lead to similar inferences. On the basis of the studies a set of mitigation strategies have been suggested.

Abstract

The Rawana landslide, located in Sirmuar district of the Shimla Himalayas, Himachal Pradesh is repeatedly active in the recent years. It is a NE-SW oriented slide with the crown in the southwest and the wider toe in the northeast resting in Giri River. During some of the sliding events emanations of heat and gases were also inferred. In order to understand the landslide phenomenon and the causative factors, and there from to evolve mitigation measures, detailed studies of the slides were under taken. The Landslide hazard zonation mapping carried out in Rawana landslide using LHEF rating based BIS method indicates that it is located in high hazard zone. The detailed studies show the complex geological, structural, morphotectonic and hydrological setting. From the studies it is surmised that the toe erosion by Giri river and the rainfall infiltration in the mid slope region are responsible for the slide. Remedial measures have been accordingly evolved.

Abstract

The Nilgiri Mountains of South India is one of the Landslide prone hill ranges in India. The landslides, in general, are due to the independent, interdependent and the combined effects of natural earth system processes, triggering phenomenon and anthropogenic activities. So the scientists, technocrats and the academicians from all over the world have started studying the landslides using various techniques and advanced tools in mapping the morphology, preparing the vulnerability maps and carve out mitigation strategies. But the discrimination of active slides is a difficult task and also needs continuous monitoring and further a time consuming process too. So, in this context, an attempt has been made to study the signatures of active sliding in one of old slides namely the “LINGASLIDE” in which frequent minor sliding events are often reported. In the study, Total station based large scale topographic survey was carried out in LINGASLIDE and from the same 50 cm topographic contours were generated. From such large scale contours, Digital elevation Model (DEM) was generated and from the DEM, shaded relief map was generated.Uutilizing both the contours and shaded relief maps, small slides were mapped in the LINGASLIDE from the well exhibited subsidiary crowns, toes and the traverse cracks. Resistivity tomography surveys were also carried out along two longitudinal profiles and one traverse profile to identify the subsurface geology, the slip surface and the zones of moisture accumulations, if any. The subsidiary crowns, toes, the conjugate fracture systems and the resistivity tomography showed that the LINGASLIDE is active and the sliding is going on towards easterly because of the easterly compression,resulted from the higher slopes caused by the settlements raised over Lingaslide and the obstruction provided by the retaining walls at the toes in the east. Such compressive forces are clear from the NW-SE and NE-SW fractures seen in Lingaslide and the sliding is clear from the cracks seen and monitored in the buildings constructed over Lingaslide.

Abstract

Kaliasaur landslide located 18km from Srinagar on the NH-58 in Uttrakhand Himalayas has been repeatedly sliding for the last over 5 – 6 decades totally paralyzing the transport operations in the region and causing beeline of issues not only for the people living in the hilly state but also the tourists and the pilgrims. The study of Geosystems & geodynamics, large scale micro zonation and geotechnical studies using RMR and SMR techniques show that the slide is located in high hazard zone and follow the pattern of wedge and planar failures with vulnerable zone of factor of safety. The toe erosion by the acutely turning Alaknanda river and the mitigation measures in the form of slope disturbance in the upslope part rather protecting slide, has been responsible for the recurring slides. The study further revealed that excessive rainfall is also a triggering parameter and the crown part is widening. On the basis of the studies, mitigation measures have also been brought out.

Keywords: Kaliasaur landslides, Micro LSV zonation, Factors of landslides, Mitigation.

Abstract

Since the landslides have started spreading over to the most of the mountain provinces of all over the world, having developed expertise in Landslide vulnerability mapping, Factor of safety, Rock mechanic studies etc. the scientists and the technocrats have started focusing towards developing landslide early warning systems using instruments. As the instrumentation in such vast areas is not feasible satellite based monitoring of landslide movements is fast emerging. In this connection the paper discusses InSAR interferometry based landslide movements carried out in Nainital and Mansadevi areas, Uttrakhand Himalayas, India.

Keywords: SAR interferometry, Monitoring movements, Nainital & Mansadevi Landslides.

INTRODUCTION

Landslides pose greater threats to the population of India also, especially those living in mountainous regions, the top being the Himalayas. Many villages and vital transport routes are endangered by landslides and losses of lives and important infrastructure now become a routine phenomenon. Therefore, studies on surface displacements and landslide movements have become very important. However, due to the large aerial extent of the landslide prone provinces, this task may not be effectively carried out by ground based methods. In the recent years, the availability of interferometric Synthetic Aperture Radar (InSAR) data from a variety of satellite and airborne remote sensing sensors has emerged, as a potential tool that can yield accurate data on surface displacements. Although, monitoring of such low velocity deformations, as we observe in landslides, is only possible if considerably long time series images are available. InSAR derived displacement measurements are not only feasible but also moderate in their costs compared to many ground-based methods. This paper discusses Small Baseline Subset (SBAS) algorithm used to monitor landslide movements.

Abstract

The landslide is a disaster which causes rampant loss to life, property and ecosystems. With increased awareness and technological development, the number of monitoring stations near hazardous regions have increased. To give warning prior to the occurrence of a landslide, the soil/rock mechanics of the underlying bed needs to be studied and understood. This paper examines the current literature and elucidates some features of state-of- the-art landslide monitoring systems.

Keywords: Field based sensors, Wireless sensor network, Landslide monitoring

INTRODUCTION

Advancements in technology have helped us to understand nature better than before, yet the geotechnical parameters causing landslides could not be quantified accurately. The efforts taken in predicting landslides are clearly moving towards this objective and this can be seen by the number of monitoring stations that have been setup in landslide prone areas around the world. The data that is obtained at each location is important in understanding landslides. Each location is unique in terms of soil properties, groundwater, inclination of the slope and weather conditions and consequently, each deployment is unique.

The paper narrates the instrumentation based forewarning systems functioning around the world. The paper discusses these aspects hierarchically viz; Landslide prone areas in India, geotechnical instrumentations and their merits, influence of rainfall on landslides, correlation between rainfall and pore pressure, the relevance of different systems for different scenarios etc.

Abstract

The Himalayas of Himachal Pradesh is prone to landslides due to inherent geodynamic conditions, rainfall and anthropogeny. Besides multi-variate studies on the landslides of Himachal Pradesh, instrument based early warning system was attempted by taking Jhakri landslides as the test site. Various instruments viz; piezometer, vertical inclinometer, Rain gauge, etc. were installed and the paper discusses about the methodology adopted in the installation of the instruments and the observations made from the instruments. While Piezometer did not reveal much information, the Tiltmeter showed minor movements.

Abstract

The present study deals with the slope instability analysis of a vulnerable stretch of 16 km between Pratapgarh road intersection and Mahabaleshwar town, which is a part of the state highway-72, Satara district, Maharashtra, India. The highway remains closed during the monsoon seasons, due to the recurrent instances of cut slope failures. So the present research work was conducted with an aim to study the reasons, extent and mechanism of the cut slope failures along the road sections as well as optimization of tools for the assessment of road cut stability of the area. The 16 km stretch was divided into seven vulnerable sections (M1; near Mahabaleshwar - M7; near Poladpur) based on the geological, geometrical and structural attributes. The slope forming mass primarily consists of laterite, weathered basalt and fresh jointed basalt, which are interbedded with red bole at some sections. Limit equilibrium, finite difference and finite element simulation were performed for seven cut slope sections, using similar geometries and material strength attributes for all the analyzing techniques. The assessment was carried out for both dry and saturated conditions to emulate the monsoons. The factor of safety yielded through the limit equilibrium method was the most conservative of all the tools; while the finite element method gave the least conservative figures in terms of factors of safety, being close to the field observations, the safety factor results of finite difference methods were between the limit equilibrium and finite element methods. The cut slope sections composed of weathered basalts and laterites (M1, M2, M3, M6) were found most vulnerable to failure during rains, while the sections composed of fresh jointed basalts (M4 & M5), though overall stable, are susceptible to planar and wedge failures.

Abstract

Geological conditions in the Tertiary mountainous areas of the western and eastern hill ranges of Manipur often cause landslide movements. These repeatedly occur mostly in old landslide regions during rainy seasons on a large scale, causing considerable economic loss and injuries and deaths of humans. In order to improve such landslide hazard assessment of the region for effective mitigation, Electrical resistivity surveys were conducted using Schlumberger array technique on the very unstable and problematic frontal part of the Kotland landslide, NH-37, Manipur along three profiles. Electrical resistivities aided the characterization and quantification of the subsurface rock units, structure and tectonic conditions of the Landslided area which can contribute for the better planning of mitigation strategies. The results lead to the elucidation of depth of the different litho-units and the geometry of failure surface. The probable failure surface was observed between 10 and 22m depth, characterised by low resistivity (< 150 Ωm) and geometry of the sliding surface was rotational. In addition, a fault was also inferred in the resistivity pseudosection model and hence the area may be highly vulnerable to landslides.

Abstract

Due to fragile lithology belonging to Disang and Barail groups of the Cretaceous-Tertiary period, intensive structural deformation related to collision tectonics, extensive weathering and the anthropogenic activities in the form of slope cutting for the development and widening of roads lead to frequent landslides in the state of Manipur, India. In this connection, the road section between Tengnoupal and Sita has been studied to understand the landslides vulnerability and to evolve mitigation strategies. The study involved the Petrochemical analysis to elucidate the weathering potential of the rocks, kinematic analysis to understand the network of joints and the strain, slope stability analysis to prepare Land Hazard Zonation mapping and estimation of factors of safety in selected locations. On the basis of these studies, long & short term remedial measures were suggested to mitigate the landslide hazards.

Abstract

The state of Nagaland located in the northeastern part of the Indian subcontinent is also prone to landslides similar to the other north eastern states due to the softer lithologies, intense deformation and extensive anthropogenic activities. So in order to understand the landslide vulnerability and to evolve remedial measures, a 12 km stretch of the NH-2 from Kohima town in the south to Zhadima junction in the north was studied. The study comprises the preparation of landslide hazard zonation map using BIS method and detailed studies in six major landslides involving RMR, SMR and Kinematic analysis and also the suitable remedial measures for such landslide phenomenon.

Abstract

The softer rock types belonging to Tertiary period, intense deformation and the related more frequent tectonic weak planes, high degree of weathering and extensive road cutting are the inherent systems in provoking Landslides in Noney-Nungba segment of NH-53 in the state of Manipur. So Landslide Hazard Zonation mapping was carried out in this segment using BIS method and also geotechnical investigations were carried out in Awang Khull part-II slide and Raungdai slide and on the basis of type of failure and the morphotectonic conditions mitigation strategies were suggested.

Abstract

Similar to other north eastern states of India, the state of Manipur is also prone to recurring landslides. The National Highway 150 and the state Highway in Ukhrul, Nunghar and Paorei sectors often witness landslides due to geological complexities, rainfall and anthropogenic activities. So a study was conducted to prepare the landslide hazard zonation map for the region using the method developed by Bureau of Indian Standards, which indicates that 67.32 km² (nearly 56%) fall under high hazard zone. The RMR and SMR studies carried out in five test sites in such high hazard zone show that four sites fall under highly unstable category (class IV) and one under partially unstable category (class III). The kinematic analysis indicates dominant wedge failure. The improper landuse, lack of adequate drainage and toe removal for road widening are the major causative factors for the recurring landslides.

Abstract

Landslides are the most common hazards in hilly regions. Rapid development and the resultant uncontrolled interactions with ecosystems are the major reasons for the landslides, besides the rainfall. So, the assessment of landslides hazard vulnerability is a prerequisite before making any developments related to settlements, hill resorts, hydropower projects and the related network of Ghat roads. The present study deals with the assessment of landslides in two different sites; Site-1 located in the Ghat section of Yercaud hills between 10/4 and 29/6 km stones in the southwestern slopes of Shevroy hills, Salem, and the Site-2 located in the Ghat road between Lower camp and Kumuli in Theni districts, Tamil Nadu. The Theni ghat road in the National Highway-220 is connecting Tamil Nadu with Kerala and is the lifeline for Sabarimala, Tekkadi and Munnar. Besides, a series of pan stacks conveying water from Periyar reservoir in Kerala to the power house located at Lower camp in Tamil Nadu also lie in this stretch of hills. Landslide vulnerability mapping was carried out in an area of 130sq.km in Site-1 and 6.7 sq.km in Site-2 by assigning numerical values to the causative factors of slope instability such as lithology, structure, slope morphometery, relative relief, land use and land cover, and ground water conditions following the BIS code No. 14496 (1998) for preparing landslide hazard zonation maps. The study in Yercaud hills revealed that out of 12 slope facets, facet 1 to 6, 9 and 12 fall under moderate landslide hazard zone whereas facets 7, 8, 10, and 11 fall under high hazard zone. The area falling in facets 3, 4 and 5 of Kumuli ghat section fall under high landslide hazard zone, the slope facets 1, 2, 9 and 10 fall in the moderate hazardous zone and other facets in low hazardous zone.

Abstract

Prediction of the occurrences of Landslides requires a set of complex analyses, involving multitude of factors which are to be studied systematically in order to evaluate the landslide vulnerability. The increasing availability of computer-based tools and data storage capabilities are found to be useful in landslide vulnerability mapping. One such significant tool in landslide studies is Geographic Information System (GIS). In this article some approaches were made to model the land slide hazard for Sirumalai Hills, Dindigul District, Tamil Nadu, India using Geographical Information Systems and the same is presented in this paper.

Abstract

The landslides have become the fast spreading disaster all over the Indian sub-continent. As such landslides were mostly occurring in the Mighty Himalayan Mountains, it was all along attributed to active tectonics. But when it started occurring in most of the mountain belts of India, various geological parameters, the anthropogenic phenomenon and rain fall were inferred to be the main causes for the landslides. Hence when this concept emerged, and again the Remote Sensing and the GIS technologies have phenomenally evolved, different types of variables, again on different resolutions and different methodologies have been adopted to prepare landslide vulnerability maps and this has started yielding varying types of outputs. As the landslide vulnerability zonation mapping (LVZ) is the first step in landslide studies it is essential to evolve a suitable methodology for the same. So the present study was carried out in a test site of around 300 sq.km in between Coonoor and Otacamund, Nilgiri mountains, Western Ghats, South India. In the said study, a set of 12 Earth System Parameters/Variables which could contribute to landslide vulnerability were prepared as GIS raster databases from the data interpreted from satellite MSS data and field geological and geophysical data sets. Similar GIS database was generated on 144 landslides. These landslides were superposed over such 12 Earth system parameters data and landslide vulnerability weightages were assigned to each subvariables of these Earth system parameters. In assigning weightages using such landslide incidence data various methods viz; slope, integrated terrain, information value, weight of evidence, index overlay and BIS methods were used and landslide vulnerability zonation maps were prepared adding all the 12 weightages assigned Earth system variables. In this, all the 12 earth system parameters were having same resolutions. Then the outputs were compared which revealed that the information value method is the best suited method for LVZ mapping followed by weight of evidence method.

Abstract

The Sonapur landslide located in the south eastern fringe of Shillong Plateau falls in NH44 connecting Shillong with Agartala. The slide is repeatedly active and massive debris flows occur during every monsoonic season since 1999. The studies carried out under the NRDMS funded project shows that the slide falls in the tectonically active E-W Dauki fault system, which not only forms the southern boundary of the Shillong plateau but also the near vertical plane along which the Shillong plateau has been uplifted due to the northerly compressive force and the collision of Indian plate with Eurasian plate. Such post collision tectonic uplift and the southerly tilt of the Shillong plateau in its southern part, monoclinal southerly dipping sediments south of Dauki fault, Sylhet trough, occurrence of NE-SW sinistral (shears) and NW-SE dextral faults in Sonapur area, high seismic activity and rainfall are responsible for the Sonapur Landslide.

Abstract

Northeastern part of the Indian subcontinent is seismically an active region, and is further prone to excessive rainfall and frequent landslides, which cause disruption of the road networks during the monsoonic months every year. The region owns a typical morphotectonic setup where many active thrusts and faults have carved out the landforms and physiography of the major part of the region. The creeping phenomenon of the N-S trending prominent strike-slip fault, namely the Churachandpur - Mao Fault (CMF), is one of the triggering factors for the frequent landslides and low magnitude earthquakes. The life line of Manipur, the national high way NH39, traverses along and in close proximity to this fault in Manipur, and hence the life is paralysed in the area during the monsoonic months. From the GPS campaign mode studies on the western and eastern sides of the CMF, it is observed that there is a change in the crustal velocities from 16 - 22 mm/yr in the east to 33 - 42 mm/yr in the west. Micro-deformations are also observed in the form of displacements respectively with the vertical, N-S and E-W components of–0.111 mm/yr (downward), 0.03 mm/yr (northward) and –0.011 mm/yr (westward). The net displacement is 0.126 mm/yr with an azimuth of N 85° and dipping of 13° towards west. Neotectonic movements along the CMF, as per the GPS measurements, suggest an aseismic nature of the fault with dextral component. Fault plane solutions of the earthquakes show northerly directed principal P-axis indicating the extension (T-axis) along east-west. The resultant creeping of micro-deformation towards the western slopes of the terrain is aligned with the principal T-axis. The creeping triggers the micro seismicity as well as the landslides along the CMF.

Abstract

Landslides have become a recurring phenomenon in most of the mountainous regions of the world. In Indian peninsular, the landslides which were mostly confined to the tectonically active Himalayan Mountains once, have started spreading over to the other mountain belts of the Peninsula. The Tirumala – Tirupati hills, which is drawing millions of pilgrims from all over the world is facing landslides especially along the newly built southern uphill ghat road. The geology of the area, studied using Geomatics tools like Remote Sensing, SRTM based Digital Elevation Models, GPS Survey, etc., showed that Tirumala hills is under the grip of upward tectonic movements as evidenced from the N-S and E-W oriented Pleistocene faults, intensely dissected Plateau top Cuddapah Quartzites, retreating escarpments, exhaustive debris slope, extensive valley fills along the slopes, colluvial fills in lower slopes, palaeo debris flows along the southern and western obsequent slopes of the Tirumala hills etc. All these indicate the inherent landslide vulnerability of the slopes. The E-W trending dykes which are piercing the slopes and protruding as ridges add further landslide vulnerability to such fragile slopes. So, the new ghat road laid along such southern slope is obviously facing landslides. However, the detailed Geomatics based studies show that the dykes, valley fills and steep slopes are particularly more vulnerable to landslides. Though remedial measures have been broadly evolved, abandoning the southern uphill new ghat road and widening the older northern downhill ghat road seems to be the better and long term feasible alternative to prevent Landslides in the area.

Abstract

The article briefly narrates the initiatives taken by the Department of Science and Technology, Govt. of India, New Delhi in providing solutions to rapidly growing Landslide Disasters in India. Duly considering the importance of the issue, the DST has embarked on a National Landslide Programme more than two decades ago and brought voluminous information on Landslide Vulnerability Mapping, Site Specific Landslide Investigations, Landslide Kinematics, Instrument Based Forewarning etc. by funding large number of research projects to various Academic/Research institutions in the country. In addition, the bilateral collaborative programme launched on Geohazards between India & Norway, resulted in bilateral flow of knowledge and capacity building amongst various tiers of the Academic, Research and the Planning Hierarchy, yielding tangible benefits.

Keywords: Landslides in India, DST’s Initiatives.

INTRODUCTION

Landslides cause extensive damages to roads, bridges, human dwellings, agricultural lands, forests and other establishments year after year resulting in immense losses of life and properties. The entire Himalayan region has been the target of intense development activities for the last few decades. Hence the instabilities along the natural slopes are accentuated by the human activities since the development schemes are often not properly planned and implemented (Valdiya 1980; Thakur 2001). This has become the case in most of the mountains in India. Keeping in view of the stability of the slopes, the need of the hour is to achieve sustainable development of the hilly regions while implementing various developmental schemes. So there has to be a major S&T role to play to minimize the landslide problems. This should include all possible corrective and preventive measures to minimize the losses due to this disaster.

Abstract

The recent disastrous tsunami of December 26, 2004 has not only alarmed the administrative and the planning machinery to have tsunami mitigation strategies for India. But also signalled the geoscientists to have a deeper look on the phenomenon of tsunami and the vulnerabilities of the Indian coasts. In this context, the authors have conducted a study primarily to evaluate the responses of the coastal Geosystems to the tsunami inundation, as it is a very vital component in f raming strategies for mitigating the effect of tsunami. The study has revealed that the central coastal parts of Tamil Nadu, namely Cuddalore – Nagapattinam districts, which were worst affected by the recent tsunami, expose a combination of landforms of tectonic, fluvial, fluvio – marine and marine processes. These different landforms have responded differently to the recent tsunami viz: as facilitators, carriers, accommodators, absorbers, barriers etc. on the basis of the same, different eco – friendly, cost effective and result oriented methods are suggested to mitigate the effects of tsunamis.

Introduction

Tsunami is an unfamiliar term and also a scantily referred term in the dictionaries in India till December 26, 2004. Even the students of geosciences were all along been taught about the origin and impact of tsunamis by citing examples from the Pacific Ocean. But the term tsunami has now become a widely known and a commonly deliberated phenomenon in India amongst various cross sections of the society irrespective of age and literacy. However, the historical tsunami data (USGS & GSI websites)

Abstract

Landslides have become a fast spreading epidemic in the mountain belts around the world. As both the natural geosystem and the triggering parameters this phenomenon, the scientists & technocrats from all over the world have started studying it using varying parameters and multivariate advanced scientific tools. In this connection the present study lays an emphasis on the need for giving deserving importance to one of the important geosystem parameters, namely the geomorphology in Landslide Vulnerability Mapping. The same has been accomplished by taking the Nilgiri Mountains of Western Ghats, South India as the test site.

Introduction

Landslides are the most commonly witnessed geohazards in mountainous systems of all over the world causing greater and recurring loss to Man, his properties and to his various developmental programmes. As these landslides mostly occur after heavy rainfalls, it was considered as the most important triggering parameter for the landslides. In indian subcontinent, the landslides of Himalayan region while were inferred to be predominately due to Active tectonics (1,2,3,4,5,6,7,8,9,10) landslides of Westernghats of Maharastra were explained to be the effect of extensive weathering and the rock falls from the cliff and the summit zone (11,12) but in contrast, the landslides of Nilgiri mountains have been attributed to deforestation, direct entry of rain water into the soil system and the resultant pore pressure increase (13,14,15,16,17,18,19,20,21) but the studies carried out (22) in the Nilgiri Mountains indicated that various geosystem parameters viz: Lithology, Structure, Geomorphology, Slope etc., occur in various permutations and combinations and assign different landslide vulnerability grades to the land systems and when such vulnerable zones are interfered by the triggering parameters, the landslides occur.

Abstract

Landslides have become a recurring phenomenon in most of the mountainous regions of the world. In Indian peninsular, the landslides which were mostly confined to the tectonically active Himalayan Mountains once, have started spreading over to the other mountain belts of the Peninsula. The Tirumala – Tirupati hills, which is drawing millions of pilgrims from all over the world is facing landslides especially along the newly built southern uphill Ghat Road. The geology of the area, studied using geomatics tools like Remote Sensing, SRTM based Digital Elevation Models, GPS Survey, etc., showed that Tirumala hills is under the grip of upward tectonic movement as evidenced from the N-S and E–W oriented Pleistocene faults, intensely dissected Plateau top Cuddapah Quartzites, retreating escarpments, exhaustive debris slopes, extensive valley fills along the slopes, colluvial fills in lower slopes, palaeo debris flows along the southern and western obsequent slopes of the Tirumala hills etc. All these indicate the inherent landslide vulnerability of the slopes. The E-W trending dykes which are piercing the slopes and standing as ridges add further landslide vulnerability to such fragile slopes. So, the new ghat road laid along such southern slope is obviously facing landslides. However, the detailed geomatics based studies show that the dykes, valley fills and steep slopes are particularly more vulnerable to landslides. Though remedial measures have been broadly evolved, abandoning the southern uphill new ghat road and widening the older northern downhill ghat road seems to be the better and long term feasible alternative to prevent Landslides.

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:

6.1 Introduction

Stratigraphy is the branch of geology which deals with the study of rock layers (strata) and layering (stratification) in their chronological order. It is primarily used in the study of sedimentary and layered volcanic rocks in order to interpret geological history and age. The term historical geology is also used as a synonym of stratigraphy but in a wider sense, it deals with the whole sequence of events that make up the history of the earth from its origin and age relations of rock strata, evolution through its life form, and structures. The scope of stratigraphy is very wide; it involves description and classification of layered sedimentary rocks and also of igneous & metamorphic rocks. The study involves correlation between different areas like lithological characters, fossil content, geophysical and geochemical properties including absolute radiometric dating.

6.2 Principles of Stratigraphy

Stratigraphy is based on the following few principles:

6.2.1 Law of superposition

In a sequence of horizontal sedimentary rock layers, the younger layers are on the top and the older layers are at the bottom. To put it another way, in a normal sequence, each bed is younger than the bed beneath it. Geologists today use it as the basis for a bed-by-bed analysis of geological history in a given area. This is important to stratigraphic dating, which assumes that an object cannot be older than the materials of which it is composed. This law known as "Law of Superposition" was first proposed by the scientist Nicolas Steno in the 17th century.

The remains of animals and plants of past ages preserved in the rocks are known as fossils, the study of which forms the subject of Palaeontology. The conditions for an animal or plant to become a fossil are firstly it must possess skeleton of some kind or some hard parts, since the soft parts are decomposed rapidly, secondly the organism must be covered up by sedimentary layer, otherwise it will soon crumble to pieces.

5.1 Modes of Preservation of Fossils

The conditions in which fossils occur depends, on their original composition and on the material in which they are embedded. The chief types are as follow:

5.1.1 The entire organism preserved

Occasionally the soft parts of the organism are preserved as well as the skeleton, the whole having suffered very little change. Instances of this are the woolly rhinoceros and mammoth found frozen in the mud and ice in Northern Siberia. Insects encased in fossil resin, known as amber, are found in the Oligocene beds in the Baltic shores of Persia, but the soft part of organisms are rarely preserved.

5.1.2 The skeleton preserved almost unchanged

Sometimes where the skeleton alone is preserved, it remains almost in its original condition, except that it has lost its organic matter. Thus the shells in the Pliocene beds of England differ from living ones only in being lighter, more porous and generally colourless. In some instances a certain amount of mineral matter, such as carbonate of lime, has been added to the skeleton, making it heavier and more compact.

The earth's crust is made up of minerals and rocks. Minerals are inorganic substances with a definite chemical composition, whereas rocks are mixture or aggregates of minerals. Each mineral is composed of certain elements present in fixed proportion. For example, mineral quartz, SiO₂ is a compound of the elements silicon (Si) and oxygen (O) combined in the proportion of 1:2, so its chemical formula is SiO₂, whereas rock granite is a mixture of several minerals like quartz, feldspar etc. Nature has provided unique physical properties to different minerals that can be used to identify them.

4.1 Physical Properties of Minerals

Majority of minerals contain following properties that can be used to identify them in field and in laboratory: crystal habit, cleavage, hardness, density, luster, streak, color, tenacity, magnetism, and taste.

4.1.1 Crystal habit

The faces that develop on a crystal depend on the space available for the crystals to grow. If crystals grow into one another or in a restricted environment, it is possible that no well-formed crystal faces will be developed. However, crystals sometimes develop certain forms more commonly than others, although the symmetry may not be readily apparent from these common forms. The term used to describe general shape of a crystal is habit.

Some common crystal habits are as follows: