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The Baikal Basin Is Extending

May 17, 2002

For millions of years Lake Baikal has remained a deep-water repository of relic fauna and pure fresh water, although its basin is constantly being filled up with the alluvion brought by violent landslides, slide-rocks, mudflows and rapid tributaries. Obviously, to keep the balance the basin should extend at least by the volume of delivered sedimentary. Doctor Boris Agafonov from the Institute of the Earth`s Crust has made calculations and proved that the volume of the incoming alluvion is four times less than that of the increment of the basin, the latter extending due to the internal earth`s crust processes.
      
Lake Baikal is known to be located in a seismically active area, the geologic age of the area being comparatively young. The elongated basin of Lake Baikal is actually a rift trough. Similar formations can be found on the bottom of all the oceans. The scientists believe that the rift troughs had been expanding for millions of years and ultimately transformed the earth`s crust break-ups into huge oceans which cover three quarters of the Earth. From this point of view the unique lake is a prototype of a prospective ocean. According to the satellite data, the Baikal basin is extending at a speed of approximately 5 mm per year, this being equal to the 20-million cubic meter increase of its volume. However, Doctor Agafonov points out that this is not the only process, which prevents the lake from being filled up by the alluvion. On top of that, the volume of the lake is increasing due to the subsidence of the basin original bed.
      
Seismic profiling of the earth bulk enables the scientists to clearly observe this phenomenon. However, unlike the rift trough enlargement, the earth`s crust is not subsiding constantly, but only in the course of powerful earthquakes. Thus, during the 9-number earthquake in 1959 the Baikal basin got instantly increased by 200 million cubic meters. In 1862, after the disastrous earthquake shocks, a bay was newly formed within the boundaries of the lake (the bay was named Proval which means `Hole`), and consequently the volume of the lake water increased by 1 billion cubic meters.
      
For the comparative analysis purposes, the scientist had to calculate the amount of alluvion coming into the lake as a result of landslides, landslips, mudflows, river floods and due to some other reasons. It has turned out that in total all the above provides no more than 10 million cubic meters of alluvion per year. The lake volume decreases by approximately the same annual amount due to the fact that parts of the bank are submerging under the water. It is worth noting that the major part of the incoming alluvion (approximately 3 million cubic meters per year) is drawn away by the Angara River waters flowing from Baikal.
      
The final calculation proves that due to internal processes in the earth`s crust the hollow has increased almost by 4 billion cubic meters since 1862 (the data for the analysis has been available since that time). The lake volume has reduced only by one fourth of the above value because of the delivered alluvion. The rest of the expansion volume is so big that exceeds by 1.5 times the volume of Lake Balaton, one of the largest European lakes. This significant additional volume was filled up primarily by the river-water, rain-water and ground water. Part of the expanded volume was taken up by potentially precious natural energy resources, i.e. oil products and gas-hydrates. The general conclusion made by Agafonov is that the unique lake basin is expanding, it is not shallowing or silting, consequently, the supply of the pure Baikal water is also growing up.

Informnauka (Informscience) Agency