Guardian: Volcanoes that spewed out lava and noxious gases for more than half a million years paved the way for dinosaurs to rule the Earth by wiping out their competitors, scientists say. The environmental devastation wrought by relentless volcanic activity at the end of the Triassic period 200m years ago laid waste to animal species that lived alongside the early dinosaurs, giving them the upper hand in the Jurassic period that followed. Before the rise of the dinosaurs, the animal …