Mass extinction is an event in which a very large number of plant/animal species die out. They die out because their population shrinks to a size that the death rate is more than the birth rate. due to asteroid strike and blockage of sunlight for several years can cause reduced heat and chilling effect on Earth causing many plants and animals to go extinct. This is called impact winter. It is also believed that impact would have produced fire storms and complete devastation over 1000 sq kms around it, before impact winter sets in.
