Palaeoclimate change during Glacial Periods: Evidence from Sri Lanka

In the Earth’s history, there were five major glaciations, namely, Huronian (2,300 Ma),Cryogenianor Sturtian-Varangian(850-635 Ma), Andean-Saharan (460-430 Ma, Karoo (360-260 Ma) andthe Quaternary (2.58 Ma to Present) that occurred between 2,300 Ma and 0.0114 Ma. It is revealed thatGondwanaland emerged between the Huronian glaciation (2300-2100 Ma) in the Paleoproterozoic Eraand the Andean-Saharan glaciation (460-420 Ma) in the Early Paleozoic Era. During this time, mostcontinental land masses were clustered in the southern hemisphere, and Sri Lanka was part of theGondwanaland landmass comprising present day Africa, Madagascar, India and Antarctica. Within theOrdovician (485.4-445.2Ma) to Permian Periods (299.0-254.2 Ma) there were signs of the breaking up ofGondwanaland resulting in the severing of India and Sri Lanka together and subsequently Sri Lanka fromIndia. By end of the Permian Period (260 Ma) Karoo Glaciation had ended and the present Mannar Basindeveloped within a deep canyon (about 4-7 km deep) on the Precambrian basement.Although the island of Sri Lanka presently lies in the Indian Ocean between 5º 52´N-9º 54´N and79º 30´E-81º 55´E, to the southwest of Bay of Bengal and southeast of Arabian Sea, it was positionedwithin 67ºS-65ºS and 34ºE-43ºE during the Lower and Middle Jurassic Era (201.3-166.1 Ma). Huge rockyblocks (erratic boulders) have been transported to different places by continental ice sheets due to climaticchanges in the Permian, Triassic and Jurassic Periods, but erratic pebbles (2 to 8 cm or more in size) andstreams fed deposits have been transported by glacifluvial processes. These glaciofluvial processesoccurred on four occasions during the Jurassic Period and Eocene, Miocene and Pliocene Epochs on SriLankan landmass, which fallowed the climatic changes and sea level fluctuations that broke up thesedimentary beds, initiating establishment of the present topography and structural configuration. As aresult, the earlier sedimentary deposits were obliterated from greater part of Sri Lanka. During theQuaternary Period the erosional rate increased and the resultant erratic boulders along withglaciofluvialdeposits can still be found on “Planated Surfaces”of Sri Lanka

GRANITE QUARRYING PROJECTS AND THEIR IMPACT OF THE ENVIRONMENT

Surface and subsurface charnockitic gneissic boulders of the Kolonna DivisionalSecretariat area have been separated-and detached using bores and compressor machines toproduce "blocks" for export. Four granite-quarrying projects were in operation at theLanka-Beriya Estate, Bulutota Kadamuduna, near the Circuit Bungalow at BulutotaKadamuduna and at Udahakanda village (Pitakanda). However quarrying in the above foursites has been abondoned stopped consequent to pressure brought by the public. Only oneproject is active at the Aigburth Estate in Suriyakanda to date.This study aims at identifying the existing problems of the quarrying projects, examineshow these quarrying projects can contribute to slope failure in the future; and makesrecommendations as mitigatory measures for better understanding of uses and themanagement of resources. Accordingly, following conclusions can be made regarding theexploitation activities in the sites:(a) local relief and other geographical parameters (physical and social) have not beengiven and concern prior to exploitation of the resources(b) damaged and destroyed boulders and fragments have been dispersed and havedumped in the sites(c) reservations made by Ordinances and Laws for natural streams (Poddana,Bulutota and Ittakanda GNDs), electrical transmission lines and cemeteries(Ittakanda GND) have been ignored during these exploration(d) after removal of boulders, pits burrows have not been filled properly withcompacted earth(e) trees and vegetative species have been destroyed and growth retarded due tooperations carried out (Bulutota Kadamuduna, Aigbirth Estate and Udahakandavillage(f) vibration during drilling and dynamiting (dynamiting is not presently used) havecreated surface cracks in the area immediately behind the boulders(g) dust from drilling operations ace removed by wind and create environmental andhealth hazards(h) development of gullies and surface erosion is caused by heavy rains after blocksare removed; and(i) closed pits as well as the open pits of the area are able to create gullies by surfaceerosion and can store an extensive volume of water increasing sub-surface erosionIt is evident from detailed field inspections and slope analysis around the sites that illegaland unmethodical quarrying of these boulders in whatever form contributes to slope failureand exerts a negative impact on the environment. The threats to human life and property aswell as the degradation of the environment has contributed to a strong opposition by thepublic to the operation of quarries

Understanding the River Basin Classification of Sri Lanka

The need has arisen to understand the rivers and river basins as a subject for achieving related policy making, development, conservation and management goals. The interpretation of the river basins concept was first attempted by Hunting Survey Corporation Limited, Toronto, Canada, and Surveyor-General of Ceylon (Sri Lanka) in 1962. Consequently, Arumugum in 1969 explained that the island could be divided into 103 components of natural river basins. Unfortunately, in the past six decades, misinterpretation of said river basins with rivers and misunderstanding of river drainage patterns have been identified many research articles and even in the Sri Lankan educational system. Most of the authors and scientists have misinterpreted the number of rivers in Sri Lanka as 103, and they flow radially from the Central Highlands to the sea. The present study is focused on providing clarifications of the river basin concept, rivers and understanding the drainage system of the island. Therefore, river basin maps and digital elevation models were developed to understand the river basins, river origin locations and flow patterns. These data coupled with previous field observations were then used to critically evaluate existing scientific literature. Accordingly, there are 29 rivers (15 perennial and 14 seasonal rivers) that flow directly to the sea. This could be further categorised as drowned river valley, bar-built perennials, bar-built seasonal, perennial delta estuaries, and seasonal delta estuaries. Considering the origin of these 29, only 8 rivers begin from the central highlands and its margins (over 1,200 m contour line), and most rivers/Oya emerge below the 1,200 m contour line. Another 64 rivers/Oya found out to be emptied into lagoons even though traditionally classified as flows directly to the sea. Mahsilawa, Katupila Ara, Pallakutti Ara and Rathmal Oya identified as rivers, but they connect to other rivers or salt marshes while, Bolgoda lake, Madu Ganga, Madampe lake, Telwatte Ganga, Rathgama lake and Koggola lake turned out to be back-barrier coastal lagoons mistakenly identified as rivers in the traditional classification. Also, all these originate from the coastal plain (below 100 m contour line). Hence, it is clear that there are some misreading of river basins and rivers in existing scientific studies. As this information is valuable in many ways to the country, misreading of these subjectmatters must be corrected immediately. Further studies on the river basins concept must be done analytically and the context of the Sri Lankan education system should be updated accordingly.Keywords: River basins, Misunderstanding, Radial drainage, Central highland, Sri Lanka

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Copyright © 2013, by IWMI. All rights reserved. IWMI encourages the use of its material provided that the organization is acknowledged and kept informed in all such instances. Photos: Cover photo by Prof. J. Katupotha showing fishermen engaged in fishing in the Negombo Lagoon. All photos in the text are by Prof. O. Amarasinghe. Please send inquiries and comments to