Дата публикации: 26 октября 2018
Публикатор: Шамолдин Алексей Аркадьевич
Номер публикации: №1540507612

Lake Baikal - the deepest inland body of water in the world-has been in the focus of attention of experts in different fields. In the autumn of 2003 a range of associated problems were on the agenda of national and international meetings of ecologists, biologists, economists, geologists, geophysicists and geographers. Considerable attention was given to an analysis of the Russian legislation "On the Protection of Lake Baikal" as a factor of consistent regional development. The Chairman of the Siberian Branch of the Russian Academy of Sciences, Acad. Nikolai Dobretsov, singled out three closely related sets of problems: the inadequate legal base, the absence of an effective system of federal administration and incomplete studies and monitoring of the unique lake.

In recent time there was a campaign in the mass media here against the problem of mounting pollution of the Baikal, mainly by industrial wastes. But, according to Acad. N. Dobretsov, current studies show the satisfactory conditions of its ecosystems with levels of toxic metals being considerably below the maximum permissible, posing no immediate threat to the local wild-life populations of the omul and seals.

And there must be good reasons for this optimism. But it is fuelled, so to say, by the very large volume of water in the Baikal which means that its chemical composition cannot be changed at a stroke. But say what you may, the problem of local pollutions is there.

Looking at the surrounding area, the greatest damage to the landscapes is done by forest fires. As Acad. N. Dobretsov pounted out: "In recent time this has been turning into a major ecological problem of this region." He also warned that the adoption of the Land Codex of the Russian Federation has paved the way to large-scale privatization of lands of increased natural and social value.

The above assessment of the two "danger points" was shared by another expert- Deputy Director of the Institute of Geography of the Siberian Branch of the Russian Academy, Prof. Alexander Antipov. He said: "Building construction is progressing now all along the: coast of the lake. And this is being done without proper ecological assessments of such new projects. New build-up areas have no clearly defined borders or development plans... In 2003 close upon one mln hectares of forests were destroyed by fires..."

This situation is especially alarming bearing in mind Prof. Antipov's view that "Baikal can feed us all and that... its image and reputation can boost the

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social-economic progress of this region".

Bearing all that in mind, what can and should be done to remedy the situation? This question was on the agenda of a recent international conference (Baikal, 2003) "Economic Development and the Environment: Information, Modeling and Management". The participants discussed prospects for stable economic development of the region on the basis of optimal utilization of its natural resources (minerals, forests and water) and of the associated aesthetical and cultural factors.

The region of Lake Baikal, attractive as it is for tourism and recreation, is also important as a major biospheric natural preserve. This was discussed in an interview by Prof. Semen Sherman, Dr. Sc. (Geol. & Mineral.) of the Institute of the Earth Crust of the RAS Siberian Branch. He described the region as "a unique site for geologists. Local geological outcrops include some of the most ancient rocks of 1.5 bin years and also the youngest ones (sedimentary rocks in troughs) of thousands and tens of thousand years of age. Because of the stretching of the litho-sphere and its upper segment-the earth crust-what is known as the Baikal rift system is developing on the border between two big structures: "Siberian Plate" and "Trans-Baikal Plate". These two platforms are drifting apart, producing a big crust fracture, or rift.

The aforesaid is one of the most popular hypotheses, although there are also assumptions concerning the origin of the unique lake and depressions on its south- eastern and north-western borders. According to one such theory * this is the "birthplace" of a whole new ocean. A similar opinion was voiced by the famous 18th century natural scientist, Acad. Pyotr Pallas. In his view Lake Baikal is located in a vast rift between diverging mountains.

According to other and more recent hypotheses, a major synclinal fold was formed there opposite to a dome-shaped lift of the earth crust. The last assumption, despite its seemingly paradoxal nature, appears to be more preferable because structures of this kind split up at the top, in the linear deformation or extension zone. And many experts now explain the formation of the lake on the basis of global plate tectonics.

The above list of hypotheses attests to the complexity of tectonic structure and geological history of this region. While on the whole there prevail extension phenomena, one can observe intraplate crustal compressions in some areas with many bigger and smaller blocks of the crust shifting in vertical and horizontal directions. Such shifts are very rapid by geological standards with rock being broken up by tremendous stresses which also cause earthquakes.

It was not accidental that this area was chosen as the site of an All-Russia conference "Lithospheric Stresses, Its Deformations and Seismisity". All of these phenomena are clearly expressed there and some of the shocks have catastrophic results, such as the formation of the Proval (cave-in) Bay ** .

In his report at the aforesaid conference Prof. Sherman spoke of some characteristic connections discovered in recent years: "We have demonstrated that the main line of seismic threat passes partially through the Tunkinskaya and South-Baikal depressions and partially outside them. We singled out the line of the Baikal-Charsky rift which has been described as the present-day zone of destruction in the lithosphere. "Superimposed" upon this line have been all the major earthquakes in Pribaikalye (near-Baikal) region. And it has become clear which geological structure "controls" these events. With a team of colleagues we are now trying to clarify the order of occurrence of seismic events within the confines of the aforesaid territory. And this is a significant step forward towards the prognostication of major seismic events."

While the Pribaikalye region is being hit by repeated tremors, the comparatively young volcanoes are located much more to the east-on the Patomskoye highland. How can this fact be explained? This geological problem, which many specialists have tried to explain, remains an intriguing scientific puzzle to this day.

Such theoretical problems, however, have direct practical links as has been proved, among others, by the builders of the Severo-Muysky tunnel on the Baikal-Amur (BAM) railway line. The construction was delayed for several years by some unexpected problems. The builders expected in that region some permafrost like in the nearby zones. It turned out, however, that thermal water was circulating through the numerous cracks in the rock. An unpleasant surprise of this kind is explained by the unusual tectonic activities of this territory.

Summit it up, for earth scientists the Pribaikalye is a most interesting "testing site" for a whole range of studies, such as comprehensive studies of the lithosphere-this rock shell of the planet. And the existence of the large body of water accounts for a range of climatic peculiarities of the region which are of particular interest for meteorologists and climate experts as well as for specialists in many other fields-from landscape experts to geo-morphologists. Incidentally, it was on the basis of his studies in Pribaikalye that Acad. V. Obruchev founded some one hundred years ago the new discipline of neotectonics which investigates current and relatively recent (on the geological time-scale) movements of the earth crust...

In the final analysis, however, one comes to the conclusion that time has come not only to pay serious attention to the protection of Lake Baikal, but also to organize a program of comprehensive studies of the surrounding territories. And it clearly goes without saying that these efforts can produce tangible results of both theoretical and practical value.

Nauka v Sibiri (Science in Siberia), 2003

Prepared by Rudolf BALANDIN

* See: G. Ufimtsev, "Studies Around Baikal", Science in Russia, No. 3, 2001. - Ed.

** See: G. Ufimtsev, "Enigma of the Proval Bay" in this issue. - Ed.

Опубликовано на Порталусе 26 октября 2018 года

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