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 era began in the wake of the PermianâTriassic extinction event, the largest well-documented mass extinction in Earth's history, and ended with the CretaceousâPaleogene extinction event, another mass extinction which is known for having killed off non-avian dinosaurs, as well as other plant and animal species.