Mesozoic

The Mesozoic Era is an era of Earth's geological history, lasting from about 252 to 66 million years ago. It includes three important periods called the Triassic, Jurassic, and Cretaceous Periods. This era is famous for the rise and fall of the dinosaurs and many other fascinating creatures.

During the Mesozoic, the world looked very different from today. The climate was generally warm and humid, and the supercontinent Pangaea began to break apart into the continents we know now. This era is often called the Age of the Dinosaurs because these huge reptiles were the main land animals for most of this time. They came after a huge event called the Permian–Triassic extinction event, which wiped out many life forms, and they ended with another big event, the Cretaceous–Paleogene extinction event, which marked the end of the dinosaurs.

Many new kinds of life appeared during the Mesozoic. The first mammals showed up, though they stayed very small. The first flowering plants also began to grow, which would later change the world’s forests. Birds evolved from some kinds of dinosaurs, starting with archaic birds and later true toothless birds. The Mesozoic was a time of great change and adventure in Earth’s history.

Naming

The phrase "Age of Reptiles" was introduced by the 19th century paleontologist Gideon Mantell, who thought this time period was mostly ruled by reptiles like Iguanodon, Megalosaurus, Plesiosaurus, and Pterodactylus.

The name "Mesozoic" was suggested in 1840 by the British geologist John Phillips. It means 'middle life', coming from Greek words for 'between' and 'animal, living being'. The Mesozoic is the middle era between the Paleozoic ('old life') and the Tertiary, and it is also similar to the Cenozoic ('new life') and the Proterozoic ('earlier life') times.

Geologic periods

Following the Paleozoic, the Mesozoic Era lasted about 186 million years, from 251.902 to 66 million years ago until the Cenozoic Era began. This time is split into three main parts, called periods: the Triassic Period, the Jurassic Period, and the Cretaceous Period.

The Mesozoic began with the Permian–Triassic extinction event, a time when many plants and animals died out. It ended with the Cretaceous–Paleogene extinction event, which might have been caused by a big space rock hitting Earth. This event led to the end of the dinosaurs, except for birds, which are considered modern dinosaurs.

Paleogeography and tectonics

The Mesozoic Era had gentler movements of Earth's plates compared to the time before it. One big event happened in the Arctic, forming mountain ranges like the Innuitian orogeny and the Brooks Range.

During this time, the huge landmass called Pangaea began to break apart. It split into two smaller continents: Laurasia in the north and Gondwana in the south. This splitting created the edges of continents we see today, like along the Atlantic coast. By the end of the Mesozoic, these continents had moved closer to their current shapes, though not their exact positions. Laurasia became North America and Eurasia, while Gondwana divided into South America, Africa, Australia, Antarctica, and the Indian subcontinent.

Climate

The Triassic period was generally dry and very seasonal, especially in the middle of the huge landmass called Pangaea. Far from the coasts, temperatures changed a lot, and large deserts likely existed. However, there were times with more rain, like during the Carnian Pluvial Event and near the end of the Triassic.

During the Jurassic, sea levels rose because new ocean floor was forming, which pushed water upward and flooded coastal lands. As Pangaea broke apart, it created more shorelines. The weather became more humid, temperatures rose, and then stabilized. Deserts became less common.

The Cretaceous climate is a bit unclear, but many think that there was a lot of carbon dioxide in the air, making temperatures roughly the same everywhere and about 10°C warmer than today. Oxygen levels in the air may have changed during this time, but scientists aren't sure exactly how.

Life

The Mesozoic Era saw many changes in plant and animal life on Earth. On land, gymnosperms like conifers and cycads were the most common plants. One special plant from this time is the Ginkgo, which still exists today as Ginkgo biloba. Later in the Mesozoic, flowering plants began to appear and spread from the tropics toward the poles.

Many new animals appeared after a big event at the end of the Permian Period wiped out many species. Dinosaurs, pterosaurs, and reptiles like ichthyosaurs and plesiosaurs became common. The Jurassic Period was a time of great diversity for these archosaurs, and it was also when the first birds and advanced mammals appeared. Insects also evolved and diversified during this time. In the oceans, tiny plants called plankton changed from being mostly green to types with red-algal-derived plastids, possibly because certain metals became scarce in the water.