The Cretaceous in Montana, US

Paleontology and geology

The Cretaceous was a geologically active time in Montana. The western part of the state experienced mountain building and episodes of violent volcanism. A broad coastal plain extended eastward to meet the Cretaceous Interior Seaway. Periods of high sea level interrupted times of terrestrial deposition. Climates were warm, with wetter conditions near the coast and seasonally arid ones in the shadow of the mountains. Terrestrial ecosystems supported a wide diversity of plants and animals, including the dinosaurs Deinonychus, Maiasaura, and one of the most famous, Tyrannosaurus rex.