At the time the dinosaurs arose, all of the Earth’s continents were connected together in one land mass, now known as Pangaea, and surrounded by one enormous ocean. Pangaea began to break apart into separate continents during the Early Jurassic Period (around 200 million years ago), and dinosaurs would have seen great changes in the world in which they lived over the course of their existence. Dinosaurs mysteriously disappeared at the end of the Cretaceous Period, around 65 million years ago. Many other types of animals, as well as many species of plants, died out around the same time, and numerous competing theories exist as to what caused this mass extinction. In addition to the great volcanic or tectonic activity that was occurring around that time, scientists have also discovered that a giant asteroid hit Earth about 65.5 million years ago, landing with the force of 180 trillion tons of TNT and spreading an enormous amount of ash all over the Earth’s surface. Deprived of water and sunlight, plants and algae would have died, killing off the planet’s herbivores; after a period of surviving on the carcasses of these herbivores, carnivores would have died out as well.
Despite the fact that dinosaurs no longer walk the Earth as they did during the Mesozoic Era, unmistakable traces of these enormous reptiles can be identified in their modern-day descendants: birds. Dinosaurs also live on in the study of paleontology, and new information about them is constantly being uncovered. Finally, judging from their frequent appearances in the movies and on television, dinosaurs have a firm hold in the popular imagination, one realm in which they show no danger of becoming extinct.