Part 1 Printing the Circuit Board. 1. Choose a method to use for creating the PCB. Your choice will usually be based on the availability of materials needed by the method, the technical difficulty level of the method or the quality of PCB you desire to obtain.
Permian-Triassic Extinction. In this video segment from Evolution: Extinction!, geologist Peter Ward shows rock layers laid down during the Permian and Triassic periods. The Permian layers contain abundant animal fossils and fossilized traces of animals, while the Triassic layers are almost devoid of fossils, suggesting a mass extinction event occurred 250 million years ago, at the end of the Permian.
The Permian period, which ended in the largest mass extinction the Earth has ever known, began about 299 million years ago.The emerging supercontinent of Pangaea presented severe extremes of climate and environment due to its vast size.The south was cold and arid, with much of the region frozen under ice caps.he Permian, however, represented the last gasp for much early prehistoric life. The period, and the Paleozoic era, came to a calamitous close 251 million years ago, marking a biological dividing line that few animals crossed.