END OF DIANOSAURS

THE END OF THE DINOSAURS

           
                Dinosaurs were the largest and the most successful animals on land. Then about 65 million years ago, they became extinct. Scientists have developed many theories to explain their extinction. The two major theories involve : (1) gradual climate changes and (2) the collision of a large asteroid with the earth. According to the first theory, it was a time of great mountain building, so the climate became more varied everywhere around the globe. Winters became too cold and summers too hot for dinosaurs to survive. Thus, death and extinction came as a result of gradual climatic changes.
            The other major extinction theory, which is quite popular today, claims tht a large asteroid hit the earth. The asteroid impact would have thrown billion of tonnes of dust and debris into the atmosphere. Heat from the impact may have caused huge fires worldwide. Together, the clouds of smoke and debris, would have blocked sunlight from reaching the surface of the earth for many months. without light, the plants stopped growing and died. Without plants, the plant-eating dinosaurs would have starved to death. As the plat-eaters died, so did the flesh-eating dinosaurs that fed on them.


            Most scientists, however, feel that no single theory completely explains why dinosaurs suffered extinction.They argue that a combination of causes may have contributed to their extinction. In fact, experts now believe regard birds as living dinosaurs that survived extinction.