Triassic Triassic The Triassic () is a geologic period and system which spans 50.6 million years from the end of the Permian Period 251.9 million years ago (Mya), to the beginning of the Jurassic Period Mya. The Triassic is the first period of the Mesozoic Era. Both the start and end of the period are marked by major extinction events. The Triassic began in the wake of the Permian–Triassic extinction event, which left the Earth's biosphere impoverished; it would take well into the middle of this period for life to recover its former diversity. Therapsids and archosaurs were the chief terrestrial
Intermontane Islands Intermontane Islands The Intermontane Islands were a giant chain of active volcanic islands somewhere in the Pacific Ocean during the Triassic time beginning around 245 million years ago. They were 600 to long and rode atop a microplate known as the Intermontane Plate. Over early Jurassic time the Intermontane Islands and the Pacific Northwest drew closer together as the continent moved west and the Intermontane Plate subducted. About 180 million years ago in the Mid-Jurassic time the last of the Intermontane Plate subducted and the Intermontane Islands collided with the Pacific Northwest, forming parts of British Columbia, Canada. The Intermontane