Extinction is one of the important phenomena in the evolution of organisms. Extinction of a species occurs when organisms cannot adapt to sudden changes in the environment. The Earth is a very dynamic planet and resists many external changes leading to the stability of biological conditions. But in some cases environmental changes are very severe. Among the most important factors of environmental changes is the collision of Meteorites to the surface of the Earth. In the early Cretaceous and the Late Eocene, the Earth was exposed to several Meteorites, which resulted in destruction of many creatures. In all Meteorites, the amount of iridium element is much higher than that of land deposits.
Therefore, by finding more than the usual quantities of iridium on the Earth's layers, it can be held as possible that a Meteorite has hit the ground. Of course, it should be noted that in some cases the element of iodine accumulates in some sediments due to diagenetic factors.