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.
Kirk Janowiak, Eclectic, educated, and loves to teach. Views. There is only one cause for mass extinctions and that is a major or equally massive change in the environment a large scale. Any wide-scale event or series of events that can alter the regional or global climate and/or environment over a large area can, thus, trigger a mass extinction. Such events might include: