Planet Earth is always changing. Areas of land (continents) move slowly around on Earth’s surface, changing the map of the world. The climate swings from warm to cold, and the plants and animals change from one era to the next, sometimes dramatically. Scientists divide the age of the dinosaurs into three periods, all of which were very different from today’s world.
251–200 million years ago
In the Triassic period, Earth’s land formed a single continent called Pangaea. The coast and river valleys were green, but much of the interior was desert. There were no flowering plants; instead, tough leaved plants such as cycads (a palmlike tree), ginkgos, horsetails, and conifers flourished (all of which are still with us). Early dinosaurs included Herrerasaurus, Plateosaurus, Chindesaurus, Coelophysis, and Eoraptor.
200–145 million years ago
Pangaea broke into two continents around 200 million years ago, with oceans spreading over what had been land to create enormous shallow seas. The Jurassic saw the emergence of giant, plant-eating sauropods (such as Brachiosaurus and Diplodocus) and large predators (such as Allosaurus). Lush forests spread across the land and the deserts shrank. Common plants included conifers, monkey puzzle trees, and ferns.
145–65 million years ago The continents continued to break up during the Cretaceous. As a result, dinosaurs on different continents evolved in different ways, giving rise to many new species. Tyrannosaurus emerged, as did Triceratops and Iguanodon. Flowering plants appeared; early species included magnolias and passion flowers. Dense forests contained trees we know today, such as oak, maple, walnut, and beech.
Today Earth’s land is divided into seven major areas that we call continents: Europe, Africa, Asia, North America, South America, Antarctica, and Australasia. All the continents are still moving, but very slowly—at about the speed your fingernails grow.