The sun is the natural source to all life. Without it there cannot be life. But the sun is so powerful that it does create dangerous substances such as the most common ultraviolet rays. Ultraviolet rays create a small amount of radiation which is harmful to all living organisms. It also is known to cause cancer as well, which is fatal. The best way to protect yourself is simply to stay in the shade. Hair and clothes also provide a lot of protection as well. This is where the ozone layer comes into effect to fend off these hazardous and dangerous  rays.

The ozone layer is like a protective shield against these rays. It blocks most of the harmful energy that the sun sends to the surface of the earth. The ozone layer is roughly 1 ½ miles high in the atmosphere and is transparent to the naked eye. This ozone layer can be damaged by pollution and it's common to hear from scientists that automobiles and big industries are causing damage to the ozone layer. Of course there wasn't cars in the Triassic, Jurassic, and Cretaceous period so ozone should've been in perfect condition during these huge reptiles roamed the earth. Actually there is one natural disaster that can damage the ozone layer really bad. Volcano's.

Dinosaur diggers have found that when they dig up dinosaur fossils that are dated from the Cretaceous period they also find a lot of volcano rock in the same area. This is very common, but only for the Cretaceous period. Knowing that, dinosaur researchers were able to assume that during that time they was many outbreaks of volcano's.

When a volcano erupted it not only sprays millions of gallons of hot lava, but also a mass of a certain chemical called  Hydrochloric acid. This poisonous gas can deface the ozone layer. One volcano would do much harm but scientists know that during the Cretaceous period there was not only one, but mass amounts of aggressive behavior by volcano's around the world.

Most Dinosaurs did not have fur, and many were known not to be like crocodiles laying in water all of the time. This is proven by the way that their bodies are shaped. So we know that they ran around land and if the ozone layer broke apart than cancer is free to spread throughout the world. This would be the beginning of dinosaurs dying off. As for other creatures such as mammals, most of them have fur which does provide enough protection that enough could've survived to get through the ozone damage until it repairs.

If you check out other Dinosaur extinction theories you'd realize that many are linked to volcano's because of the proof of that timeline and the loads of volcano rock material found at the same ground level as the latest found dinosaur fossils.