eChapters

Most of us consider weeds to be the troublesome, competitive, aggressive, undesirable, unsightly elements of the plant world. We hate weeds since desirable plants cultivated by us are deprived of food, water, sunlight and space by these plants. They can easily colonize an area and thrive even under non-ideal conditions of growth and may affect human welfare adversely. It is perhaps due to this that the saying, when weeds win all the people lose, has come into existence.

The terminology committee of the Weed Society of America gives the simple definition of weed as a plant growing where it is not desired. King (1974) in his book Weeds of the World observed that ‘‘a plant classed as a weed in one region where it has few, if any, uses may when growing in another region, possess some very valuable uses, or in few cases may actually be cultivated’’. For instance, Bermuda grass (Cynodon dactylon) is a highly troublesome weed in crop fields, but in village pastures, it is a much sought for forage grass. Quack grass (Agropyron repens) is a very good soil binding grass on erodable non-crop lands but it is a serious weed when it infests crop fields and orchards. Campbell (1923) considered weeds as ‘honest, independent competitors for food materials in the struggle for existence’. He pointed out that the term, weed has developed in the minds of people not according to specific qualities or by a definite concept in the mind of man, but by human caprice, e.g., corn is a cultivated crop, hence, desirable plant in a corn field. However, if a corn plant grows in a Soya bean field, it is considered a weed by the Soyabean farmer. Sometimes, two persons may differ about the weedy nature of a plant at the same place and time, e.g., water hyacinth (Eichhornia crassipes) is a weed for fisherman but it is a plant of aesthetic value for a city dweller.

Thus, a corollary to the above definitions of weed is that weeds are those plants, which grow out of their place, interfere with the utilization of natural resources, prolific, persistent, resistant, competitive, harmful and even poisonous in nature and can grow under adverse conditions.

Mulching is a practice of covering the surface of soil with plastics, organic and non-organic materials like straw, grasses, sands, stones (boulders), synthetic plastics, etc. to reduce evaporation and to moderate wide fluctuations in diurnal soil temperature, especially in the root zone environment. It controls external evaporability and reduces energy supply to the evaporating site by cutting off solar radiation falling on the ground. Its main function is limited to control first stage of drying, which helps in improving moisture status and reducing soil temperature (Loy and Wells, 1975), besides checking seedling mortality and improving crop stand. It also suppresses weed-flora and reduces weed competition with crop for water and nutrients making them available in greater quantities for crop plants. Moreover, mulching helps in increasing downward movement of water, and its storage deep in the profiles escapes evaporation due to reduction in thermal gradients and exchange of vapours. The effectiveness of mulches in conserving moisture has generally been found to be higher under more frequency of rainfall, drought conditions and also during early period of plant growth when canopy cover remains scanty.

India is a major exporter of vegetables with 10th position in the world. In the past, the Dexport of Indian vegetables was restricted to potatoes and fresh onions, however, now, the Government of India finds great opportunities for expanding exports of several vegetables including lettuce, fresh peppers, tomatoes, squashes, gherkins, etc. Under World Trade Organization (WTO) regime, the development of stronger seed industry and improved production technology will give India a competitive edge in global market. New opportunities and challenges are emerging every day in the dynamic and global vegetable-based industries. However, such opportunities can be harnessed only if assured quality, in terms of organic farming and reduced pesticide residues, is maintained (Shanmugasundaram, 2004).

Increasing food need, decreasing land availability and concurrently attenuating synthetic nutrients supply envisage the use of alternate supplementary inputs for the cultivation of crops. India is among the few nations where systematic farming started thousands of years ago. It was not only the source of income but was also a way of life. Agricultural activities and the techniques adapted to suit local needs and conditions. Different farming systems were followed by the farmers in different areas according to their needs and weather conditions. The produce was usually shared with other communities of the society involved in other professions. Almost all the nutrients removed by the crops were recycled to the soil directly or indirectly (Yadav and Mowade, 2005). In economic terms, the system followed by the then farming community was highly cost effective since all the inputs needed were locally available and practically no expenditure was incurred except labour. The traditional agriculture was though less productive but self-sufficient. With the advent of modern scientific discoveries, agriculture also changed its face, and with the introduction of high yielding varieties, synthetic fertilizers and effective plant protection measures through chemicals, Indian agriculture made rapid strides in the shape of Green Revolution. As an upshot of Green Revolution, the grain production increased two and a half folds in about three decades with a marginal increase in net-area under cultivation.

Many materials can be applied to the soil as source of plant nutrients but the term fertilizer is often used to refer to relatively soluble nutrient sources with a high analysis or concentration. Commercially available fertilizers supply essential elements in a variety of chemical forms but many are relatively simple inorganic salts. Advantages of commercial fertilizers are their high water solubility, immediate availability to the plants, high concentration and low price per unit of nutrient, and the uniformity and accuracy with which specific amounts of available nutrients can be applied. Since they are relatively homogeneous compounds of fixed and known composition, it is fairly easy to calculate precise application rates and attain relatively consistent performance. This is in contrast to organic nutrient sources, which are a much greater challenge to manage because of their variable composition, variable nutrient availability and patterns of nutrient release that are greatly affected by temperature, moisture and other conditions that alter biological activity.

The solubility of commercial fertilizers can sometimes be a problem since soluble nutrients may move out of farm fields when applied in excess or large rains occur soon after fertilizer application. Soluble nutrients can be lost by leaching on well-drained soils and through tile outlets or in runoff on poorly drained soils. Denitrification can cause large losses of nitrate-N from water-saturated soils in wet springs.

Increasing soil cation exchange capacity by increasing organic matter reduces the movement and loss of some nutrients, although not nitrate-N (an anion). Management practices that synchronize nutrient availability with crop demand and uptake also minimize losses. Both application timing and the amount of fertilizer applied are important. Splitting fertilizer application into several small applications rather than a single large one is especially important to limit nitrogen leaching on well-drained sandy soils. Split nitrogen applications can also reduce nitrogen losses in runoff or from denitrification on poorly drained soils. Excess nutrient applications can be eliminated or at least significantly reduced by soil testing on a regular basis, setting realistic yield goals and fertilizing accordingly, accounting for all nutrient sources such as legumes, manure and other amendments and using plant analysis as a monitoring tool for the fertilizer program.

Soil fertility and crop production can be maintained only by efficient and judicious management of nutrients addition to the soil from external sources. Of the two sources most widely used all over the world, one is organic in nature- the organic manures, simply called manures, and the other comprises the synthetic or naturally occurring chemical fertilizers, simply called fertilizers. A brief account of manures is described hereunder:

The word manure came from Middle English manuren meaning to cultivate land, and initially, from French word manoeuvre meaning hand work alluding to the work which involved manuring land. The term manure originally meant that which was worked by hand (Fr. manoeuvre), but gradually, came to apply to any process by which the soil peroperties could be improved. Prominent among such processes was that of directly applying manure to the land, manure in this sense being what is now called farmyard manure or dung, the excreta of farm animals mixed with straw or other litter. Ronald Fisher seems to have used the word manure systematically for what we would call fertilizer today.

Uses of Manure

Manure has been used for centuries as a fertilizer for farming since it is rich in nitrogen and other nutrients, which facilitate growth of the plants. Liquid manure from pig or hog operations is usually knifed (injected) directly into the soil to reduce the unpleasant odours. Manure prepared from hogs and cattle is spread on fields using a manure spreader. Due to the relatively lower level of proteins in grasses, which herbivores eat, cattle manure has a milder smell than the dung of carnivores, e.g., elephant dung is practically odourless. However, due to the quantity of manure applied to fields, odour can be a problem in some agricultural regions. Poultry droppings are harmful to plants when fresh but after a period of composting are valuable fertilizers.

The dried manure of animals has been used as fuel throughout history. Dried manure (usually known as dung) of cow was and still is an important fuel source in countries such as India, while camel dung may be used in treeless regions such as deserts.

After attaining green revolution, nutritional security is of utmost importance in the current agricultural scenario. Vegetables play a key role in providing nutritional security in the country. They are important and readily available source of mineral nutrients and vitamins and play a vital role in the financial economy of the majority of small and marginal farmers. Further, these roles are becoming more transparent in the light of agriculture diversification as the vegetables have many agro-economic advantages and can fit into varying cropping systems under diversified conditions. After China, India is a leading vegetable producer but the productivity of vegetables per unit area is very low compared to other developed countries. Poor crop stand establishment is one of the factors responsible for low productivity. Yield and productivity can be improved by using advanced technology on the field preparation, optimum sowing conditions, correct nursery practices and planting methods.

Almost all the vegetable crops are propagated by seed, except a few. Crops are raised either by direct seeding in the field or by transplanting seedlings raised in nurseries. Direct seeding is the placement of seeds at desired depth into the final location where soil environment is ideal for optimum germination and crop stand establishment. On the other side, transplanting refers to removal of actively growing seedlings from one place to another with the purpose of having them continue their growth in the new location until harvest.

The vegetable crops like peas, beans, cowpea, okra, beet leaf, spinach, fenugreek, coriander, carrot, radish, turnip, beetroot, etc. are sown directly in the field, while tomato, eggplant, hot pepper, sweet pepper, onion, leek, sweet potato, cabbage, cauliflower, broccoli, Brussels sprout, kohlrabi, kale, lettuce, celery, parsley, rhubarb, squashes, etc. are first sown in the nursery beds where seedlings are raised and then transplanted in the main field. Both direct seeding and transplanting are practiced in most of the cucurbits like gourds, cucumber, melons and pumpkin.

The directly sown vegetable crops do not respond to transplanting because their embryonic roots do not produce lateral fibrous roots after uprooting unlike transplanted crops where numerous fibrous roots are generated, thus, making the plant to absorb more nutrients.

Nursery management is indeed a very important operation in successful growing of vegetables especially those, which are raised through seedlings in properly managed nursery beds. Raising nursery from seed provides an easy and convenient way to nourish tender young seedlings in a well-managed small and compact area. The nursery area can be conveniently protected from natural hazards, seed borne diseases and insect-pests and can be well managed economically. Some of the vegetable seeds are very costly, for which it is necessary to raise nursery in the most-optimum conditions. In areas where land holdings are small (in hills), nursery raising helps in making economical use of land for about one month and provides enough time to mature for previous crop, harvesting, threshing and land preparation for next crop. Most of the vegetable crops like cabbage, cauliflower, tomato, eggplant, sweet pepper, hot pepper, onion, celery, parsley, lettuce, etc. can successfully be raised through seed by growing them in the nursery and then transplanting in the field.

“A vegetable nursery is a place or an establishment for raising or handling young vegetable seedlings until they are ready for more permanent planting.”

Nursery can be maintained either for personal or commercial purpose, and each has its own advantages and disadvantages. Seedlings raised for own planting will be true to type, sound and healthy. On the other hand, seedlings purchased from outside may not be true to type, vigorous and healthy and may not arrive at destination in due course of time.

Seed is the basic input of agriculture, and its importance has now well recognized in the food supply chain since the warranty for production could be succeeded only based on the availability of seed. Seed becomes the quality seed, on possession of specific characters, viz. germination, vigour, purity and health status, hence, seed production becomes the specified scientific technology with the foreseeing of quality and storability in addition to productivity. From time immemorial, seeds are being imposed with some management techniques for improvement in seed quality and thereby the productivity. These seed management techniques are known as seed treatments. Generally, seed treatment is the application of biological, chemical agents and physical techniques to the seed in order to obtain the benefit of plant protection, production and invigouration. Basically, seed treatments are intended to improve the quality of seeds since nothing can substitute poor quality seed, no matter how lavishly other inputs are spent on the crop established from such seeds. Even for a resource poor farmer, high quality seed would be a great advantage because it ensures the best utility of all inputs in addition to the augmentation of yield increase by 15 to 20%.

In general, seed treatment could broadly be classified into physical and physiological treatment. Physical treatment is external seed treatment, while physiological is impregnation of needy substances into the seed through various seed management techniques. Some of the germination augmenting physiological seed treatments are seed fortification, seed hardening, seed priming, dry permeation and pre-germination. In addition, some of the seeds are imposed with special treatments such as dormancy breaking treatment such as soaking in water, mechanical scarification, acid scarification, bio-scarification, scorching, warm stratification, cold stratification and electrical seed treatment. The common physical seed treatments are seed pelleting, seed coating/film coating and seed colouring. Seeds are also imposed with some other physical treatments that can act on the physiology of the seed such as irradiation, magnetic and electrical seed treatment. In addition, irrespective of seed, seeds are given with protective treatment when they are taken for storage, which are commonly termed as pesticide seed treatment. Seeds are also given with corrective treatment at their initiation reduction with seed quality characters during storage, which are termed as mid storage correction.

The importance of fruits and vegetables in human nutrition is well known. Vegetables are a rich and comparatively cheaper source of minerals and vitamins. Besides, their consumption in sufficient quantities provides taste and palatability, increases appetite and provides a fair amount of fibers. These are currently reckoned as an important adjunct for the maintenance of good health and beneficial in protecting against some degenerative diseases, thus, they form a vital part of human diet. Besides, vegetables now a day are being considered as an asset for providing a good source of income to the growers.

Vegetables originated in different parts of the world, some came from tropical or subtropical countries and others from temperate zones, some from humid areas and others from climates that are more arid. Most of the countries in the world are gifted with varied agro-climatic environments for growing an array of vegetable crops to combat the present imbalanced diet of a vast population of the world, particularly in the developing countries. Production of vegetables in developed countries is much higher, for instance in Japan, nearly 40% of the diet of the people is vegetables. To meet out the full dietary needs of the common man, to eliminate malnutrition, deficiency of minerals and vitamins and also to relieve the stress for increased production of cereals, there is a greater need for growing vegetables on larger scale. As such, for increased production of nearly 247 known vegetable crops, a sound knowledge of the various aspects of vegetable production technology, environmental stresses and constraints, techniques of raising, pre- and post-harvest technology, marketing and seed production techniques is of utmost importance. Breeding and selection of new cultivars have allowed for a greater adaptability to less favourable growing conditions than was possible in the past but the inherent agroclimatic requirements of a specific kind of vegetable have not changed materially. Time or season of planting of a particular vegetable crop is determined by its environmental requirement. Knowledge of specific agroclimatic conditions required for a particular crop could enable the grower to select the best season of planting in any particular area (Singh et al., 1991).

In view of fast development of industrial sector and rapid urbanization, the vegetable gardening of various types has great scope for providing food and nutritional security, promoting health, solving employment problem and raising the economic status of an individual and the country as a whole. In many of the developing countries, protein-energy malnutrition is the most important health problem, which has long-term ailing consequences. Iron and vitamin A deficiencies are also potent contributors towards morbidity, mortality, underweight and stunted growth of individuals. Vegetables from homestead gardens can combat these dreaded social nuisances. In many cases, indigenous vegetables, gathered or grown wild, are more nutritious than foreign high value exotic species (Drescher, 1998). Various types of vegetable farming are being practiced the world over depending on the area available and objectives for the disposal of the produce. Based on the mode of disposal, the vegetable gardening can be categorized into two types:

Olericulture, a Latin word, is used to designate the science, culture and management of vegetable crops. In India, about more than fifty vegetable crops are grown in different parts, depending on their climatic requirement. A number of vegetables have similarity in their method of cultivation, which makes the package of practices followed by the farmers for their cultivation very complicated and brings about a lot of repetition. Whichever the method is adopted for the classification of vegetables can systematize the preparation and presentation of the material to some extent and can avoid the unnecessary duplication of some of the principles and methods of vegetable cultivation. In different vegetables, different plant parts are used as food in different forms and they belong to different botanical families with varying cultural and climatic requirements but common insect-pests and diseases along with their common control measures.

Various methods may be used to classify all the vegetable crops into different categories but no single method of classification would be useful to serve the purpose for different groups of scientists like taxonomists, botanists, physiologists, horticulturists, agronomists, and breeders. Under field conditions, the classification based on cultural practices has been proved the best adaptable and very useful for the growers. Vegetable crops can be classified in the following ways for the convenience of different groups of scientist and growers:

Olericulture, a Latin word, is used to designate the science, culture and management of vegetable crops. In India, about more than fifty vegetable crops are grown in different parts, depending on their climatic requirement. A number of vegetables have similarity in their method of cultivation, which makes the package of practices followed by the farmers for their cultivation very complicated and brings about a lot of repetition. Whichever the method is adopted for the classification of vegetables can systematize the preparation and presentation of the material to some extent and can avoid the unnecessary duplication of some of the principles and methods of vegetable cultivation. In different vegetables, different plant parts are used as food in different forms and they belong to different botanical families with varying cultural and climatic requirements but common insect-pests and diseases along with their common control measures.

Various methods may be used to classify all the vegetable crops into different categories but no single method of classification would be useful to serve the purpose for different groups of scientists like taxonomists, botanists, physiologists, horticulturists, agronomists, and breeders. Under field conditions, the classification based on cultural practices has been proved the best adaptable and very useful for the growers. Vegetable crops can be classified in the following ways for the convenience of different groups of scientist and growers:

The importance of vegetables in human nutrition is now well known all over the world. Vegetables are rich and comparatively cheaper source of minerals and vitamins. Their consumption in sufficient quantities provides taste and palatability, increases appetite and provides fair amount of fibre. Besides, they provide many specific chemical substances, which are essential for growth, reproduction and for the maintenance of good health and also beneficial in protecting against some degenerative diseases (Prior and Cao, 2000; David, 2005; Elison and Levin, 2006).

Apart from their nutritive value, vegetables probably do more than any other groups of food to add colour, texture and flavour to our daily diet. Majority of the population in India is vegetarian, and thus, vegetables form an essential item of food for both the rich and the poor people. National Nutrition Monitoring Bureau (1997) surveys indicated that the daily intake of most foodstuffs in Indian households, except for cereals and millets, is much below the recommended dietary allowances (RDA). The diets provided negligible amount of protective foods. It was found that consumption of green leafy vegetables (< 10 g) and other vegetables (70-80 g) per day, which are rich source of micronutrients, are woefully inadequate. However, as per the RDA, an adult man should consume 200 g roots and tubers, 100 g green leafy vegetables and 100 g other vegetables (Table 1) in a day. In addition, fresh fruits (100 g) as available in different seasons should be consumed regularly for the prevention of chronic diseases (NIN, 1998).

Agriculture is a generic term used to include various types of farming systems, single to multiple crops under various agro-climatic conditions thereby covering crop husbandry, animal husbandry, vegetable growing, floriculture, horticulture, fishery, poultry, goat rearing, piggery, rabbit rearing, sericulture, forestry, vermi-composting, etc. Indian agriculture is a symbiosis of various production systems, a way of life or a tradition, which for the centuries have shaped the thoughts, the outlook, the culture, and the social and economic force of rural life. It is well known for its multi-functionalities of providing employment, cultural heritage, livelihood, social security, family bondage, nutritional and food security. Although agriculture is the main stay of the Indian economy and supports nearly two-third of the work force, yet this is not a highly rewarding enterprise for a large majority of farmers who hold small and marginal size holding. At the same time, the size of the land holding is on a gradual decline, while contribution of farmwomen is on an increase as men go elsewhere in search of better jobs. This sector holds and will continue to be central to all strategies of socio-economic development of the country. A farmer is a multi-purpose entrepreneur (Rajavanshi, 2007).

The basic feature of the Pre-British India was a village, which was economically a water-tight compartment fulfilling the three basic functions of economy, i.e., production, distribution and consumption, within the village community without outside world dependence, except the salt and kerosene. Every village was a self-sufficient unit with dependence on agriculture carried out by community people of different castes having the occupational specialization with interdependence, viz. jajmani system and alike.

Developments in the means of communications and the opening of Suez Canal in 1869 introduced fundamental and far-reaching changes in the social system and economic life of Indians by transforming self-sufficient village economy to new modes and means based on competition, market and price mechanism. This change was deliberated by Britishers for meeting the requirement of raw material and the diversification to tea, jute and indigo took place. Cotton also got importance but agriculture did not find place for vegetables. Famines were very common and crop production depended on monsoon rains to the large extent. Britishers developed cotton, jute and mineral trade for their vested interests.

Britishers emphasized the development of railways for better mobility of their troops, commercial crop produce and minerals but the Report of Famine Commission 1901 bitterly criticized the Government for the step-motherly treatment given to irrigation facilities as compared to railways. The irrigation policy of the Government in 19th century was determined purely from concerns for adequate returns on investment and profit was of Rs. 81 lakhs after paying 4% interest on amount invested on irrigation development in 1896-97. Irrigation Commission was established and a sum of Rs. 42 crore was spent on irrigation by 1911. By 1930, about 30 million acres were brought under canal irrigation, which was far larger than the irrigated area in any other country of the world. Even in the USA, the area under canal irrigation was two-third that of India. Vegetables cultivation did not find place in Indian agriculture and also in diet of villagers. Their cultivation remained restricted to the periphery of the urban centres for meeting the demand of upper class elites only.

Since the dawn of civilization, the human species had an intimate association with fruits, roots, nuts and other vegetables that sustained them through the ages. This mutualism continued and flourished through domestication and organized culture of horticultural crops. Pretty long before, homestead gardening had been evolved in different parts of the globe independently to become a part of tradition in almost every society. Plant domestication by all likelihoods started around the human settlements. The obvious reasons for this were man’s need, better supply of water and organic household wastes and protection against destruction or grazing by animals, that’s why the prospective horticultural enterprise of homestead gardens all over the world is still the most enduring and sustainable form of family food production system and very important micro-units for conservation of plant genetic resources. The traditional and indigenous endeavour of the tribal people for conservation of land races also noteworthy contribution from one generation to the next. Though cereals are staples for most of the world population, there has been sustained emphasis on horticultural crops, particularly vegetables, all over the world during last few decades. The possible reasons are:

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:

3.1 Introduction

Crystallography is the science of crystals. The term crystal is derived from the Greek word “Crystallos” which means “ice”. The term was used for colorless quartz which was believed to be “fossilized” ice. Crystals are bodies bounded by flat surface, arranged on a definite plan which is an expression of the internal arrangement of the atoms. They are formed by consolidation of magma which is also considered as crystallization.

3.2 Terms in Use to Describe a "Crystal"

3.2.1 Faces

Faces are the plane surface in a crystal. The common faces are usually parallel to net planes containing the greatest number of lattice points or ions. Wide spacing between the net planes leads to development of faces in these planes. Faces are two types like and unlike faces.

2.1 Introduction

Topographic expression is the replica of geological structures present within the earths surface. When various types of rocks of an area are displayed on a map (sheet of paper), it is known as Geological Map. Normally geological maps prepared on topographic maps. Surface topography is best presented by contour lines on a plain paper.

The importance of geological maps is to understand the nature of structure and distribution of surface outcrops with their relation to contour lines. Horizontal and dipping beds are easily identified on map because, horizontal beds runs parallel to contour lines while inclined beds cut through different contours. The angle and direction of dip can be calculated from geological maps. Geological maps are of great importance to civil engineers, after studying geological maps and consultation with geologists, civil engineers can advice for construction of engineering structures like excavation of road cuttings and construction of canal, bridges, dams and tunnels etc. Geologists get vital clues about the geological history of an area, and can draw a cross section of an area and know the structure present underground.

1.1 Geomorphology

Geomorphology is the scientific study of the origin and evolution of topographic and bathymetric features created by physical or chemical processes operating at or near the earth's surface.

The surface of the earth is unstable and affected by a combination of surface and geologic processes that cause tectonic uplift and subsidence. Surface processes are mainly physical and chemical action of water, wind, ice, igneous activity and activities of living organisms on the surface of the earth. Upliftment of mountain ranges, the growth of volcanoes, isostatic changes in surface elevation and formation of deep sedimentary basins are categorized under Geological processes.

Main geomorphological processes occurring in nature are as follows:

1.1.1 Aeolian processes

Aeolian processes include activities of the winds, its ability to shape the surface of the earth. Wind acts as an effective agent of erosion, transportation and deposition materials, and large supply of fine, unconsolidated sediments. Aeolian processes are important in desert (arid) environments.

1.1.2 Fluvial processes

Moving water in a river channel, is able to mobilize sediment and transport it downstream. The rate of sediment transport depends on the availability of sediment itself and the discharge by river.

River originates from mountain with V shaped valley, which later increases in size, merging with other rivers. The network of rivers thus formed is known as drainage system. These systems show four general patterns viz. dendritic, radial, rectangular, and trellis etc. In the mature stage, the river form alluvial flood plains, meanders and ox-bow lakes. Finally when it merges to ocean, forms delta.

reach out their fingers it is gone” - Chinese Philosopher Lao Tzu Tao Te Ching. True to his verses, geohazards are phenomena regulated by the law of natureand it is beyond the human intellect to understand thoroughly and capability to conquer. This is the lesson learnt by us from so many incidences that geohazards cause greatest havoc wherein natural processes are going on and are inhabited by humans. Greed for natural resources and population pressures on the earth’s resources are the causes of many a catastrophic event. Examples in this regard are galore including, damning river courses and location of urban centers along rivers and coasts – flooding, cyclonic storms, tsunami hazards; alteration and deforestation hill slopes for agricultural and construction activities – landslides; unscrupulous utilization of ground water resources – drought, etc. This chapter is an attempt to draw the attention of human communityasa whole toturn towards learning to live with the nature without alterning the natural processes to get rid of impacts of geohazards as a best ever mitigation measure. In other words, this chapter attempts to emphasize the need to change our attitude to escape from natural hazards instead of attempting to tinker around natural processes only to get battered at the end.

INTRODUCTION

Oxford English dictionary states that the word ‘disaster’ is derived from the 16^th century French word ‘disastre’, which is a combination of two terms namely, ‘Des’ meaning bad or evil and ‘astre’ means star. Thus “desastre” signifies a ‘bad star’ or ‘evil star’. Disaster, therefore, implies loss or damage occurring due to some unfavorable star. However, in terms of modern knowledge, the word ‘disaster’ denotes any odd event, whether natural or man made, which can bring about sudden and great miseries to humanity in the form of loss of life or/ and property.

impacts other speheres and that too on a distal place! This chapter explains how global warming affects remote places like highlands of Bhutan. Severe hot summers during the year 1994 led to excessive melting of glaciers in the higher Himalayas. The exceptional melting contributed enormous amount of melt water to the lake basins, which caused breach of the morainic dam and consequent enlargement of the outlet of the Luggye Tsho and the Tshopda Tsho, Bhutan. Floods followed the breach on October 7, 1994. These floods destabilized the slopes on either bank of the Pho Chhu near Tshopda Tsho outlet making them prone to landslides. The flash floods also eroded the left lateral moraine of the Raphstreng Tsho, which had disturbed the original angle of repose. The Raphstrcng area is also prone to ice avalanches, rock glaciers, surge of which can damage the rim and also cause spillover of water. Examination of geological, geomorphological, geotechnical, microclimatic and hydrographic information in and around the glacial lakes led to improved understanding of breach characteristics based on which mitigation measures were suggested and implemented in the years 1996-97. Since then the lakes have remained intact. From this case study and satisfactory performanceof mitigationmeasures suggest that similar integrated studies have to be conducted for thorough understanding of hazard prone areas based on which mitigation measures have to be implemented for successful reduction of impacts.

INTRODUCTION

The Lunana area, situated in the northern district of Gasa, is one of the most extensively glaciated terrains of Bhutan (Fig. 1). In response to the general global warming, these glaciers like those of other parts of the Himalaya are in a state of steady retreat, often leaving behind a chain of lakes. Though the glacial lakes endow scenic beauty, they also pose environmental hazards, due to frequent bursting of their morainic dams and consequent flash floods. The last lake-burst occurred on 7^th October 1994, leading to floods in the Pho Chhu River. Following floods, the Geological Survey of India in collaboration with the Royal Government of Bhutan, investigated the Lunana area to identify the causes and effects of the floods and suggest remedial measures. More than a decade had passed since the implementation of mitigation measures and there has been no such breach and flood despite continued Glacial Vetreat during to Global Warming. This chapter describes the characteristics of these glacial lakes, nature and results of the study and mitigation efforts.

This chapter sheds light on a geohazard namely quicksand. Unlike other geohazards, it waits for its victims to cause hazard. Though discounted as a myth and also as a monster problem in Hollywood film stories, phenomenon of quicksand is real and could inflict life threatening dangers. Analyses of genetic causes, associated properties and locales of its occurrences indicate that more deaths might have resulted due to panic and drowning in waters than by quicksand itself. Based on these inferences, potential mitigation measures are presented in this chapter.

INTRODUCTION

Quicksand, referred as “pudhai manal” in Tamil, is one of the lesser known dangerous natural phenomena that cause death of human and other unsuspecting animals. It is a geohazard of different sort. It is different in a sense that it never “goes” anywhere like tsunami or causes hazard like flood or landslide or any other geohazard; but it waits for hapless victims; that is., it is harmless until human beings or other fauna step into the region of quicksand. It is commonly prevalent in many river beds and other locales near water bodies located amidst dense forests. Many a deaths occur due to quicksand but go unnoticed owing to its “non catastrophic” nature. It is also a geohazard less understood pertaining to causes of formation, potential to cause damage and occurrence (www.mythbuster.com). This chapter is an attempt to review the existing literature on this geohazard for better understanding.

This chapter documents shoreline changes of the Dakshina Kannada and Udupi districts of Karnataka State for the period between 1967 and 2005 studied by comparing the SOI topographic maps with IRS-1C/1D LISS-III satellite imageries through GIS techniques. Examination of coastal geomorphology, sediment flux and effectiveness of seawalls had indicated that the 130km long coastline of Dakshina Kannada and Udupi districts is essentially stable, but for seasonal variations. It has been estimated that, out of 130km, about 55km long coast is vulnerable to sea erosion, of which, 25km is covered byseawalls and covering another 10km length underway. It is revealed through field examination that protection of coastline through these measures is satisfactory only along few patches while other stretches of seawalls simply shift the zone of erosion to adjacent coastline owing to many reasons including quality of construction, unscientific positioning of seawalls, etc. It is also inferred that same is the case of many other coastlines elsewhere including Kerala coast. These experiences warrant scientific design and implementation of coastline protection measures.

INTRODUCTION

The 130km long coastal zone of Dakshina Kannada and Udupi districts is one of the densely populated coastal zones of India. The coastline is almost straight, regular and oriented towards N22°W, N12°W and N6°W directions at south of Mangalore, north of Mangalore and north of Malpe respectively. Barrier beaches and spits, ancient beach ridges, marshes, swamps and tidal flats characterize this zone. Natural features and man-made structures interrupt the shoreline. The natural features include estuarine mouths of Netravati-Gurpur rivers near Mangalore, Mulki-Pavanje rivers near Mulki, Udyavara river near Malpe, Sita-Swarna rivers near Barkur, Kollur-Chakra-Haladi rivers near Kundapur and rock exposures near Someshwar, Surathkal, Mulur, Kapu and north of Malpe (Fig. 1). The man-made structures include one major and four minor ports; breakwaters at the Netravati-Gurpur estuary, New Mangalore Port and Malpe harbor and a number of seawalls placed at various places along the coastline (Fig. 2). All these structures/features bring about local irregularity and contribute to erosion and accretion along the shoreline to some extent. Apart from these, source of beach material, coastal processes like wave refraction, longshore current, littoral drift etc.