Based on the variation in space and time oi the composition of rift-related volcanic rocks in the Trans-Baikal region, the Cenozoic deep-seated processes are shown to be inherited from the tectonic and magmatic activity during the Mid-Paleozoic to Mesozoic. The Eastern Siberia rift system is divided into three groups of rift basins : the Tunka-Eravna group with associated volcanics formed in the Late Cretaceous to Mid-Cenozoic, and the essentially non-volcanic Baikal-Chara and Khubsugul-Darkhat groups which formed during the Late Cenozoic. Although development oi the Eastern Siberia rift system was contemporaneous with the Indian-Asian collision, the relative rotation of terranes separated by the Baikal-Chara group of rift basins around the pole at its northeastern termination, indicates that extensional forces were local. A hot spot model which proposed to explain the geodynamics within the Eastern Siberia rift system, implies a powerful heat impulse along the southern edge of the Siberian craton from -29 to -12 My (Late Oligocene to Miocene). This was expressed by doming, rifting and vigorous mildly alkaline basaltic volcanism. A migrating sequence of volcanism within the western area of the Khubsugul-Darkhat group might indicate a slow (0.8-0.9 cm/yr) eastward motion of the Eurasian plate overriding a fixed mantle hot plume.