The Western Interior Seaway expanded and receded drastically over the course of the Cretaceous period, which spanned 80 million years and ended with the mass extinction of the dinosaurs and ammonoids.

The theme for this month’s geoscience blog carnival, The Accretionary Wedge #9, is to discuss a significant geologic event. What event (or period, or feature) of Earth history has had an effect ...

The Western Interior Seaway formed about 100 million years ago when the mountains that now define western North America lifted up as a result of tectonic forces. Those same forces flexed the land east ...

The study found that average water temperatures in the Western Interior Seaway during the mid-Cretaceous ranged from 28 to 34 degrees Celsius (82 F to 93 F), as warm as modern tropical extremes ...

During the early to middle Cretaceous, ... The area just to the east of the new mountain range flexed downward, creating a shallow North American seaway (known as the Western Interior Seaway) ...

Toward the end of the Cretaceous Period 75 million years ago, sea levels were among the highest in the history of our planet. The Western Interior Seaway extended from the Gulf of Mexico to the ...

The Cretaceous Period lasted for nearly 80 million years. ... In the Late Cretaceous, for example, the Western Interior Seaway split North America into two landmasses. At its largest this sea was more ...

Inoceramus platinus was a large, flat clam that lived on the bottom of the Western Interior Seaway. It was only an inch or two thick; many adults had shells that were 3 feet across, and some ...

The Western Interior Seaway, approximately 75 million years ago. Image from Sampson SD, Loewen MA, Farke AA, Roberts EM, Forster CA, et al. (2010) New Horned Dinosaurs from Utah Provide Evidence ...

Back then, the American Midwest was a swampy rainforest, and an inland sea that has since disappeared – known as the Western Interior Seaway – ran all the way from what’s now the Gulf of ...

Parts of western Colorado were likely swampy during the Late Cretaceous period. The western part of the state was situated along the seaway's western edge, which would have included deltas ...

Hesperornis, discovered by Othniel Charles Marsh, is a near relative of modern birds that still retain teeth. It once dove for prey in the Western Interior Seaway. During the Cretaceous period — when ...