Intro: Sixty-five million years ago, some phenomenon triggered mass extinctions on the lands and in the oceans so profound that they define the geological boundary between the older Mesozoic Era, often called the "Age of Reptiles," and the modern Cenozoic Era, the "Age of Mammals." On a finer scale, the extinctions define the boundary between the Cretaceous geological symbol, "K", and Tertiary "T" periods. This mass extinction is usually referred to as the K-T extinctions. The dinosaurs became extinct during the K-T mass extinction. To examine how the K-T extinctions fit into a broader perspective, please see the The cause...
same time and since they took up soo much air it was hard for the dinosaurs to breathe , so they fianlly died.

The evidence is that the fossils found in the ground contain traces of lager traces of Oxygen.

How can humans stop this?

Since mankind is much smarter than the reptiles it is obvious that we can stop these asteroids from colliding with the earth. The only question is how. Now we have nuclear devices which can be put on these asteroids so that they can explode just in time before it"s course is doomed towards earth.