Dinosaur extinction. Computer illustration of a Torosaurus dinosaur standing in an icy landscape. Some scientists believe that dinosaurs and many other creatures were made extinct by an increasingly cold and unstable climate at the end of the Cretaceous period (65 million years ago). This climatic change is thought to be partly due to volcanic eruptions and a large meteorite which struck the Earth. These threw large amounts of dust into the upper atmosphere and blocked out the warmth of the Sun.