Although our title is Extinction of Dinasours, may be it is better to say an Extinction of Non-Avian Dinasours since fossil records indicates that birds evolved from theropod dinasours.
When we compare homos time interval with dinasours'(non-avian dinasours), there is a great difference between two of them. Homos age is estimated to be 2.5 million years while there is a 177 million years between oldest dinasour's fossil and youngest one. If we assume dinasours walked at the earth for just one day then there is only 20 minutes left for homos. The other interesting evidence is difference between two oldest fossil is 16 million years.
How Kingdom of Dinasours collapsed?
There are several theories neverthless most common and supported one is Cretaceous–Paleogene (K-Pg) extinction event which includes impact of astreoid and its effects.
In 1980, a team of researchers consisting of Nobel prize-winning physicist Luis Alvarez, his son geologist Walter Alvarez, and chemists Frank Asaro and Helen Michel discovered that sedimentary layers found all over the world at the Cretaceous–Paleogene boundary contain a concentration of iridium many times greater than normal. Since iridium is rare element in the earth, such a big amount of iridium could only came from space.
It was a good question. How could it came?
There were several ideas, though most powerful one was the differences can be caused by astreoid impact. And in 1990, this idea was supported by the discovery of Chicxulub crater in the Gulf Mexico. (180 km wide approximately half of Turkey's Aegean Region)
Although it was great impact and its inital effects were fatal, it's secondary effects were more disastrous. First of all enormous amount of dust, ash and other materials were ejected into atmosphere and this blocked sunlight and radiation. Rapid temperature decreases had changed climate and environments, this was very bad news for animals and plants which were big and need big amount of sunlight and energy. Evolution began to work and 75% or more amount of all species on Earth vanished but on the other hand a change in environment made new resources available and evolution diversify rapidly into a multitude of new forms.
