Increased volcanic activity brought about the end of the Triassic period.
The most massive extinction in Earth's history occurred at the end of the Permian period and the start of the Triassic period, about 251 million years ago. The end of the Permian ushered in frigid temperatures that killed close to 90 percent of marine life and about 70 percent of land vertebrates. As the Triassic began its reign, warmth once again permeated the land and sea. Plant and animal life changed, in conjunction with the transforming climate and geology, during the course of the Triassic. The late Triassic saw the stirrings of a new time -- the age of the dinosaurs.
Geology
By the end of the Triassic, Pangaea had become Gondwana and Laurasia.
By the middle of the Triassic, the supercontinent of Pangaea had already begun breaking apart. At the end of the Triassic, the new land masses included Gondwana -- comprising Africa, Antarctica, Asia, India and South America -- and Laurasia, made up of Asia, Europe and North America. From Alaska south to Chile, mountain ranges started forming. North Africa spread farther from Europe and drifted apart from North America. The Tethys Sea, which remained at a low level, separated the two land masses.
Climate
Because of the breaking up of Pangaea, lava flows formed at the boundaries of the North American and African plates in an area scientists deem the Central Atlantic Magmatic Province. The increased volcanic activity may have led to an increase in carbon released into the atmosphere. Carbon in the atmosphere rose threefold by the end of the Triassic. The significant increase in the amount of carbon in the air contributed to global warming. With the warming temperatures, the oceans began heating, leading to a decline in the amount of oxygen dissolved in ocean water and affecting marine life.
Flora
Evergreens such as pines thrived during the Triassic and Jurassic.
By the end of the Triassic, seed ferns such as Glossopteris, which looked like modern-day ferns, became extinct. With the decline in the seed ferns, gymnosperms such as the conifers, cone-bearing plants and the cycads, or palms, started taking over the landscape. The cycads made up about 20 percent of all plant life during the transition between the Triassic and Jurassic periods. Bennettitales, extinct plants that resembled the cycads, existed during the Triassic and continued into the Jurassic. Ginkgoes also thrived, but only one species of ginkgo has survived to the present. Angiosperms, plants that produce flowers, did not appear until after the Jurassic period.
Dinosaurs
At the beginning of the Triassic, archosaurs, the ancestors of the dinosaurs, roamed the land. The archosaurs had body types similar to amphibians and lizards, with limbs outstretched instead of placed directly underneath the body. The ornithosuchids, archosaurs that possibly represented the direct ancestors of dinosaurs, walked on two legs and tore meat with pointed teeth. True dinosaurs emerged toward the end of the Triassic, walking on two legs and eating only meat. Skeletal changes in the pelvis, legs and neck allowed the dinosaurs to support their bodies and heads. The first dinosaurs diverged into two types: the meat-eating saurischians and the plant-eating ornithischians.
Mammals
The first mammals were tiny creatures that resembled rodents. Like modern-day mammals, primitive specimens possessed a variety of teeth that were replaced once in their lifetimes. The morganucodon, an ancient mammal type, provided many fossil samples dating from the late Triassic. The early mammals continued to develop in the Jurassic, diverging into other forms.
The End of the Triassic
The tail end of the Triassic ushered in a massive extinction event. Some in the scientific community attribute these extinctions to a steep increase in volcanic activity while other scientists blame a gigantic asteroid colliding with Earth. The decline in the number of seed plants caused the ferns to increase in number. Almost all amphibian life became extinct, along with half of all marine life. Dinosaurs and conifers continued virtually untouched into the Jurassic.
Tags: marine life, volcanic activity, about percent, ancestors dinosaurs, became extinct, during Triassic
