At present Lake Baikal cavity morphologically consists of 3 independent cavities: the southern, the middle and the northern ones. The southern one stretches from the southern end of the lake to the Selenga river delta where the bottom of the lake is much higher than the adjacent parts (the Selenginskaya bulkhead). The middle cavity is located between the Selenga river and the Ushkanyi islands archipelago and then north-eastwards. The hills are named the Academicheski range. The northern cavity stretches from the Ushkanyi islands to the northern end of the lake.
The cavity of Lake Baikal is asymmetric. Its western side is steep, whereas the eastern one is more gently sloping. On the western side the shallow water platform (the shelf) is developed very little, on the eastern on it is much more greatly developed. The deep water part of the slopes is also morphologically different. Along the western coast the slope is comparatively little dismembered and there are no large forms of the underwater relief (with the exception of the extreme north-western part). The relief of the eastern shore slope if more complex. There are great underwater valleys like canyons. The bottom of the Baikal in all the three cavities is even, with a little incline westwards where the maximum depths of the lake are recorded.
In 1977 the Limnological Institute in cooperation with the USSR Academy of Sciences Oceanology Institute made visual underwater research of the underwater relief with the help of the Pisces autonomous underwater sinking device. In the southern cavity of the lake 42 dives were performed including 5 dives to the depths of more than 1,000 m. During the research the maximum depth of man’s sinking was reached – 1,410m. As a result of the research performed on the part of the lake from the Listvennichnaya bay as far as the village of Bolshie Koty a number of structures inaccessible for other methods of research were found in the underwater relief. The underwater canyons crossing the slopes cut not only the loose thick of the sediments, but also the crystalline and metamorphosed rocks the formation of which is connected with cross clefts of tectonic origin. On the underwater slopes there are steps inclined to the centre of the hollow. Their formation is probably connected with the Baikal cavity widening, the Primorsky range raising and sinking of the tectonic blocks along the Obruchev fault system breaks along the western board of the lake cavity. It is found that the underwater slopes are corroded with shingle beach material of the abrasion shores rolling down to the depth, as well as with underwater muddied flows. The erosion furrows are up to 3-5 m deep.