geologypalkbaymainpoints

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Main Points for Presentation

1. Non-assignment of Geo-technical Evaluation work of SSCP to GSI.

2. Interiors of Tamil Nadu are made up of Very Hard Crystalline rocks, while the coastal and off-shore areas exhibit somewhat hard sedimentary rocks developed in a series of ridges and basins that developed by horst-graben structures in southern Tamil Nadu.

3. The gravity, aero-magnetic and marine magnetic data over southern Tamil

Nadu supports these structures. 4. The four main deep crustal faults trending in NNE-SSW to NE-SW, NW-SE, N-

S and E-W directions show evidences of both vertical and lateral strike-slip movements even during the present day in the form of neo-tectonic activity.

5. Occurrence of a hot spot / mantle plume termed as Rama’s hot spot is inferred

in the PB-GM area, from High Heat Flow Zones II and III (similar to those in the Himalayan front), high gravity – low magnetic signatures, reported occurrences of recent extinct volcanoes off Pondicherry and Machlipatnam as well as from probable volcanic activity from marine magnetic surveys off Vedaranyam coast. The heat from these sources transmitted through the movements along the various fault zones in the area are manifested in flowing bore-wells of hot water with temperatures between 30oC and 60oC. Such hot water bore-wells are seen restricted only to the area around Palk Bay and not seen any where else in Tamil Nadu.

6. Occurrence of earthquakes all along the Tamil Nadu coast are known during the

last two centuries and the epicenter of one earthquake with 3-4 Magnitude is located within PB area. Geophysical studies indicate that areas with high gravity and high heat flow are most vulnerable for earth tremors. The PB-GM region is therefore most potential and vulnerable for future earthquakes as it exhibits high gravity – high heat flow characters.

Thus it can be seen that the PB-GM area is not only fragile with respect to tectonic movements, but also highly sensitive for higher heat flow manifestations coupled with seismically vulnerable nature.

7. The RS / AB feature is not merely a group of simple sandy shoal or sandy

bars of migratory nature as being projected by the Govt. and Project Authorities. Evidences are available to prove below such sandy bars, this physical feature forms a distinct geological, geotectonic, oceanographic and oceanic divide that has got a specific and very important role to play as a barrier in controlling the different geological and oceanographic activities in this highly fragile and sensitive area.

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8. Destabilisation of the multifarious barrier zone of RS / AB feature will bring in the following geo-environmental impacts:-.

• Tectonic movements along the active fault zones bringing about subsidence and submergence of areas with inundations and flooding as well as collapse of structures

• Causing submarine landslides which in turn will lead to changes in ocean currents and mini-tsunamis besides blocking ocean passages.

• Inducing earthquakes and earth tremors, which in turn may cause damages to structures, causing submarine land slides and other concomitant disruptions.

• Inducing movements along this fragile zone of high heat flow will bring in excessive heat to the surface, thus changing current movements, the lives of biota as well as higher corrosive and erosive effects of the hot waters causing instability to the canal and bringing about land-slides and blocking the passage of sea, etc.

Effects of Tsunamis on the PB – GM area

a) The view of Government and SSCP authorities that the SSCP canal will reduce the impact of future tsunami waves is erroneous. Running water will always flow with high velocity and energy along any new narrow linear channel.

b) Evidences are available from the Tamil Nadu coast, where in spite of reduced energy on hitting the coast, the 2004 tsunami waves moved ferrociosly inland upto 3km along the existing river channels and caused heavy devastations.

c) Tad S. Murthy, the renowned tsunami expert objected to SSCP project and suggested re-alignment the canal.

d) The Palk Straight and the RS/AB feature have acted as barrier zones and protected the PB – GM area as a tsunami shadow zone during 2004 tsunami.

e) In addition, the likely reactivation of faults due to tsunami causing future mega- earthquakes may direct the waves to move with added force along fault movements to hit the coast, as probably happened in the case of heavy damages caused to Phuket in Thailand and to the Cuddalore- Nagapattinam coast in Tamil Nadu during 2004 tsunami.

Essential Pre-project Studies

•••• In order to understand fully the sea level fluctuations and shore-line

changes as well as geo-tectonic movements through space and time, it is essential to study in detail the following data from historical as well as recent past. o Various maritime and bathymetric charts of different periods and

generations.


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o Toposheets of Survey of India on different scales and various generations.

o Aerial photos of different scales and different generations. o Integrated studies using digital enhancement and other

techniques, of satellite imageries of different spectral bands and of different band widths, from different organizations of different countries taken during various periods.

o Special studies of ‘thermal infra-red’ imageries to understand the geo-thermal conditions.

•••• Besides these remote sensing studies, the following modeling studies are also important. o Scale modeling and computer generated modeling of the

variations in oceanic current movements during different seasons, including the tidal waves and tsunamis, and their behaviour if the channel is opened, and faults are reactivated, by using data input on all related disciplines from all available sources and organizations.

o Similar modeling to be carried out to understand the nature and behaviour of the geo-environmental system when further geothermal manifestations are developed due to the project activities, by using data input on all related disciplines from all available sources and organizations.

o Similar type of modeling of both the types to study the impact of faulting and subsidence to submarine land slides and their consequential destructions and damages, by using data input on all related disciplines from all available sources and organizations.

o Fixing up of micro-seismic monitoring systems in a number of places within PB - GM area, especially at the inter-section of active fault zones, by using data input on all related disciplines from all available sources and organizations.

o Detailed geothermal studies assisted by geo-physical surveys and by drilling to understand the geothermal potential and its impact on the geo-environmental conditions, by using data input on all related disciplines from all available sources and organizations.

Recommendations

The above described conclusions arrived at from the holistic analyses of geo-scientific data from geological, geophysical, geo-tectonic, seismotectonic, geothermal and geo-environmental spheres make it imperative for the authors to recommend to the Government of India to constitute immediately two committees for the following purposes:

1. A committee of experts from the different scientific disciplines such as geology, geophysics, remote sensing, seismology, biology, oceanography and environment to review all available


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data from these disciplines covering the PB - GM and surrounding areas, and their relevance to SSCP, with special emphasis on the points raised as well as the suggestions for further studies mentioned in this paper and to recommend to the Govt. the quantum and specific studies to be taken up, as well as to monitor those studies as and when they are taken up. These members need not be only from serving scientists from different organizations and universities.

2. Another committee drawn from various Government and other organizations such as GSI, NGRI, NRSA, ONGC, NIO, NIOT, NEERI, ZSI, and BSI etc., who have the requisite man power, equipments and expertise to carry out the studies as recommended by the first committee within the stipulated time frame, and to assign such specified tasks to the identified organization/s.

3. Final decision as to how the project to be implemented may be taken by the Govt. after the results of the studies are obtained.

Does Rama’s Bridge exist? – A Geological Perspective

1. The term Rama Sethu / Adam’s Bridge has been defined and described here to represent the distinct physiographic feature that forms geological, geo-tectonic, oceanic and oceanographic divide between PB and GM areas and that probably existed for millions of years. In contrast to this feature, we would like to define the temporary bridge structure that is built by Lord Rama’s army on this basement feature as Rama’s Bridge. Usage of the two terms without proper definition by many workers and Govt. agencies have caused much confusion. 2. Many of the geographical and some geological descriptions of Valmiki’s writings are found to be accurate with the present day features, denoting the veracity and authenticity of his writings and establishing Ramayana as a historical fact. 3. Valmiki’s description of Rama’s bridge clearly states that it was built with rock boulders, earth and trees, over the pre-existing loose beach sand and other marine sediments in the seas. Thus it was a “rock and earth fill structure” supported by logs of wood. In all probability, this temporary structure would not have withstood the fury of the ocean over a period of about 5000 years sine Ramayana and would have been completely destroyed and removed. It is possible that some portions of this structure might have been preserved in rare cases where it was coved by later marine sediments and protected from destruction and erosion.


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4. Boreholes drilled along and across RS/AB feature by NIOT and SSCP have indicated that within the top 8 to 18m, two layers of loose marine sand sediments, separated by a central zone are encountered in RS/AB. 5. NIOT describes the central zone to be made up of boulders and pebbles of varied composition, such as calcareous sandstone, shelly limestone and corals and interprets it to be not due to any natural phenomenon, but probably due to human activity. 6. SSCP considers that the central zone is made up of indurated calcareous sandstone and all the three zones are due to natural processes. 7. In order to understand the true nature of this central zone it is recommended to do large scale pitting to 20m depth till the second loose marine sand zone is reached in RS/AB feature and to carry out detailed under water videography and close spaced sampling of all the four walls and the base of the pits for determining the composition and age of rocks and sediments. Unless all the above investigations and studies are carried out, the existence of the remnants of Rama’s bridge over the RS/AB feature cannot be conclusively disproved.

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