The Permian Period was a time of great crisis in Earth's history. The Permian saw the final closure of the Iapetus Ocean that had formed following the breakup of the super continent of Rodinia in the late pre-Cambrian; the closure resulting in the formation of another super-continent, Pangea. It was during the Permian that two of Earth's major mountain chains, the Appalachians and the Urals, were created. The period was one of climatic extremes. By the end of the Permian, Earth had not only experienced its most widespread glaciation but also the formation of deserts the likes of which had never been seen before. In addition to all of the physical events that were to occur during the period, the close of the Permian was the time of fue most severe extinction that has ever occurred in all of Earth's history when more than 95% of all marine life was wiped out. The Permian was indeed, a crisis in the history of Earth.
Renton, John J. and Repine, Thomas, "The Permian Period" (2016). Readings and Notes. 15.