Cretaceous

The Cretaceous was a major geological period that lasted from about 145 to 66 million years ago. It was the third and final period of the Mesozoic Era, following the Triassic and Jurassic periods. During the Cretaceous, dinosaurs lived on land, oceans were full of marine reptiles, and the first flowering plants began to spread. The period ended with a mass extinction event that caused most dinosaur species to disappear.

The world during the Cretaceous looked very different from today. Continents were still moving apart as part of a long process called continental drift. Large landmasses that would later form North America, South America, Africa, Europe, and Asia were changing shape and position. Because of these movements, climates varied across the planet. Some areas were warm and dry, while others were covered by shallow seas. These environments supported many forms of life, including dinosaurs, early birds, and many types of plants.

Plants changed greatly during the Cretaceous. Before this period, most plants reproduced with spores or cones. But in the Cretaceous, flowering plants, known as angiosperms, began to appear. They spread across many regions and provided new food sources for plant-eating animals. Fossils show leaves, seeds, and pollen from these early flowers. As flowering plants grew more common, animal groups such as insects also changed, because many insects relied on plants for food.

Dinosaurs were widespread during the Cretaceous. Some well-known species, such as Tyrannosaurus rex, Triceratops, and Velociraptor, lived near the end of the period. Many dinosaurs developed new body shapes and ways of living. Feathered dinosaurs became more common, and some early birds appeared. In the seas, large marine reptiles such as mosasaurs and plesiosaurs swam through warm waters. Flying reptiles called pterosaurs lived in the skies.

The Cretaceous also saw changes in ocean life. Coral reefs grew in warm, shallow waters. Many fish groups became more diverse, and new species of shell-forming animals appeared. These changes helped shape ocean food chains that would continue into later periods. Fossil records from Cretaceous rocks show detailed remains of shells, bones, and even impressions of soft-bodied animals.

The period ended about 66 million years ago with a mass extinction event. Many scientists think this event was caused by a large asteroid impact combined with volcanic activity and climate changes. These conditions caused most dinosaur species, along with many marine animals, to become extinct. After the Cretaceous, new groups of animals, including mammals, became more common on Earth. The Cretaceous is studied today to understand ancient climates, life forms, and how major changes shaped Earth’s history.