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.
Clues from the fossil record give us information about what species went extinct and when, but how the extinction happened in the first place has been a puzzling question for scientists. One of the biggest theories involves a series of volcanic eruptions, which took place about 250 million years ago in Siberia. According to Smithsonian's Mass Extinction, these eruptions spewed enough lava to bury the continental US under a layer 1,000 feet deep. Wikimedia Commons Part of the Siberian traps.