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.
During the PermianâTriassic mass extinction event 252 million years ago, most life on Earth perished. Scientists have now obtained evidence that ocean acidification played a key role in the die-off. The new research was published in the journal Science on April 10, 2015. The PermianâTriassic mass extinction event is the largest such event to ever to have occurred on Earth. About 90% of all marine species and 70% of all terrestrial species died off during this time. It was much worse than the mass extinction event that killed off the dinosaurs 65 million years ago.