The extinction of dinosaurs

By Jhoan Gabriel García

We know all about dinosaurs?
The dinosaurs appeared on Earth about 240 million years ago. The word dinosaur comes from the greek "deinos"and "saurd" and it means: terrible lizard.
At first, reptilsaurio was the name used to identify the new species  but Richar Owen changed this name.

We have found a lot of fossils of dinosaurs around the world. We have classified them in many species, we know what they ate, but we don`t know why they became extinct. There are different theories about their extinction.

-The asteroid collision theory:
-In 1980 a group of researchers led by the physicist Luis Alvarez found iridium concentration hundreds of times higher than normal in the layers of the Earth and the asteroids contain iridium.
It has also been discovered a giant crater in the Yucatan Peninsula. Its diameter measures 180 km.
This impact happened 65 million years ago.


-Anther theory is the multiple impact event: It explains the multiple impacts on all the world.

-Climatic change: This theory explains that the earth cooled and the dinosaurs couldn't adapt to the cold and they died. Moreover, this theory isn' t all true because there were polar animals.
-Overpopulation:
The overpopulation of herbivorous dinosaurs could devastate the vegetation and cause death from lack of food, and consequently the extinction of their predators.

-The cosmic irradiation: 
After the explosion of a nearby supernova, the disappearance of ozone or a decrease or reversal of the magnetic field that protects Earth.
Only animals under 25 kg appear to have been able to survive because throughout our history there were many mass extinctions of different intensities but this was the biggest.