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 Cretaceous also saw the first radiation of the diatoms in the oceans (freshwater diatoms did not appear until the Miocene). The Cretaceous-Tertiary Extinction The most famous, if not the largest, of all mass extinctions marks the end of the Cretaceous Period, 65 million years ago. As everyone knows, this was the great extinction in which the dinosaurs died out.