Triassic Period was a time in Earth‘s history that lasted from about 252 million to 201 million years ago. The period’s name comes from the Trias, a formation of three distinct rock layers found in Germany. Geologists first identified rocks from the Triassic Period in the Trias. The Triassic was the first of the three periods that make up the Mesozoic Era, during which the dinosaurs lived.
The Triassic Period followed the Permian extinction, the largest extinction in Earth’s history. During the Permian extinction, as much as 95 percent of all species of living things died off. The Permian extinction changed life on Earth so dramatically that it marked the end of the Paleozoic Era, the earliest era of animal and plant life on Earth.
During the Triassic Period, the plants and animals that survived the Permian extinction spread and developed into many new forms. Reptiles became the dominant animals on land and in the sea. Reptiles of the Triassic Period included the first dinosaurs and early large marine reptiles. Both of these groups would flourish throughout the Mesozoic Era. Also during the Triassic Period, the early ancestors of modern mammals appeared. Plant life during the period included some of the earliest conifers (cone-bearing plants). These plants were primitive ancestors of modern pine and spruce trees. Some early tetrapods (four-legged animals) with an amphibian way of life survived the Permian extinction but died off before the end of the Triassic.
During the Triassic Period, most of Earth’s land was arranged in a giant continent called Pangaea. This arrangement kept much of the land far from the ocean, resulting in a hot, dry inland climate. Global sea levels remained low during the Triassic, and most Triassic Period rocks formed on land. The oceans did flood parts of what is now western and southern Europe, leaving marine fossils in Triassic rocks found there. Toward the end of the Triassic, a series of valleys formed along faults (breaks in the rock layers) between what are now eastern North America and western Africa. This faulting was the beginning of the breakup of Pangaea.
Like many geological time periods, the Triassic ended with a widespread extinction. Although it was smaller than the Permian extinction, it still ranks among the largest extinctions in Earth’s history. No major groups of living things disappeared, but many species died off and were replaced by others.
See also Mammal (The first mammals); Prehistoric animal (The Age of Reptiles).
