Boreskov

OP‐1developed a theory of the great glaciations. But the very causes of the fall in averagetemperatures by at least 2‐5 °C were not clear.Many authors attribute some of globally recurring events with the motion of the Solarsystem in the Galaxy. During this movement, the Solar system have repeatedly met with thegiant molecular clouds, periodically crossed the galactic plane, passed through the branchesof the spiral structure, i.e. passed through the area of increased density of matter in thegalaxy. During such periods, frequency of close encounters of stars with Solar systemincreased. This caused disturbance of comet orbits of the outer and inner parts of the Oortcloud, which, in turn, could lead to comet showers. Hundreds of comets were transferred tohigher eccentric orbits and penetrated into the central regions of the Solar system, some ofthem collided with the Earth. But the comet's collision with Earth couldn`t lead to globalcatastrophe, it`s a local scale event.Vityazev A.V. [4] proposed a new mechanism of the Galaxy action on events on theEarth. During periods of comet showers stream of comets, moving in the direction of theSun, crosses the asteroid belt. Cross section of collision of comets with numerous asteroids ison orders greater than their cross section of collision with the Earth. Calculations showedthat the collision of a comet with an asteroid even much smaller in size but with higherdensity at an average velocity of comets in the asteroid belt about 30‐40 km/sec leads tocomplete destruction of comet and ejection of dust into interplanetary space. Estimationshave shown that during the periods of cometary showers of a dust can be formed enoughthat reduction of an insolation of the Earth has led to approach of the next glacial age.References[1]. Adushkin V.V., Vityazev A.V., Pechernikova G.V. In the development of the theory of the origin and earlyevolution of the Earth // Problems of the origin and evolution of the biosphere / Ed. E.M. Galimov.Moscow: Librokom, 2008. P. 275‐296 (in Russian).[2]. Vityazev A.V., Pechernikova G.V. Early Earth in close environment of young stars // Problems of origin oflife. Russian Academy of Sciences. Moscow: PIN RAS, 2009. P. 131‐157 (in Russian).[3]. Coryn A.L. Bailer‐Jones The evidence for and against astronomical impacts on climate change and massextinctions: A review. //International Journal of Astrobiology, 8, 213‐239.[4]. Vityazev A.V. Could be caused Great glacial ages by comet showers? // Doklady Earth Sciences, 2011 (inpress).30