There was a major change in the climate in the Cretaceous Period. During the Cretaceous Period the weather was very warm. It was considered "tropical." At around the ending of the Cretaceous Period, however, the temperature dropped making the climate very cold. The drop in temperature was caused by global cooling which is better known as "glaciation." This killed all the plants which caused the plant-eating animals to die off because there were no plants to eat. Next the meat-eating dinosaurs died because there was no meat to eat. This was a big climatic change and most dinosaurs died because of it.