Cretaceous Cretaceous The Cretaceous (, ) is a geologic period and system that spans 79 million years from the end of the Jurassic Period million years ago (mya) to the beginning of the Paleogene Period mya. It is the last period of the Mesozoic Era, and the longest period of the Phanerozoic Eon. The Cretaceous Period is usually abbreviated K, for its German translation "Kreide" (chalk, "creta" in Latin). The Cretaceous was a period with a relatively warm climate, resulting in high eustatic sea levels that created numerous shallow inland seas. These oceans and seas were populated with now-extinct marine reptiles,
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