Triassic was some sort of end-Carnian extinction, when several herbivorous archosauromorph groups died out, while the large herbivorous therapsids—the kannemeyeriid dicynodonts and the traversodont cynodonts—were much reduced in the northern half of Pangaea (Laurasia). These extinctions within the Triassic and at its end allowed the dinosaurs to expand into many niches that had become unoccupied. Dinosaurs became increasingly dominant, abundant and diverse, and remained that way for the next 150 million years. The true "Age of Dinosaurs" is during the following Jurassic and Cretaceous periods, rather than the Triassic. Triassic The Triassic () is a geologic period and system which spans
Geology of Arizona The subduction of the Farallon Plate beneath western North America remains a poorly understood event, although new seismic and computer tomography modeling is shedding light on the event. As the oceanic plate subsided under North America, it generated partial melting conditions that formed volcanoes on the surface in California and Arizona. Volcanic activity commenced in western Arizona around 205 million years ago, kicking off the Nevadan orogeny, which lasted until 145 million years ago, spanning the Triassic into the Jurassic. Granite intrusions 190 million years ago enriched many veins with minerals and generated copper porphyry gold deposits. Bisbee, Arizona, 92