Such events estimated frequency is equal to 1 every 10,000 - 100,000 years. Archaeologists and geologists have confirmed their existence. Judging by those events descriptions, they may be the results of the Earth close encounters with large meteorites. Essential part of the Earth's inhabitants may perish from the impact of one of such fragments. Many people surviving with their life hardly can live in the new environment after the collision.
Geological data are evidence of the encounters of the Earth with large cosmic bodies.
It led to extinction of the Earth's inhabitants. The global catastrophes occur once every million or more years. The most powerful of them can cause the change of geological periods and epochs. In our time probability of such changes is still in existence. Our time exceptional peculiarity is the fact that the contemporary civilization has reached a sufficiently high level of technology to discover in good time the threat of the cosmic collision and to prevent the catastrophe.