What is the Western Interior Seaway?
The Western Interior Seaway, also called the Cretaceous Seaway, was a massive waterway that covered much of the interior of North America during the early and mid-Cretaceous period, from about 100 to 70 million years ago. The Western Interior Seaway was among the largest continental seas of all time, stretching from Utah in the west to the western Appalachians in the east, a total of about 1000 km (621 mi) wide. Its deepest point was only about 800 or 900 meters (about half a mile) underwater, relatively shallow for a sea. The Western Interior Seaway also covered most of the shallow southeastern United States, including every state adjacent to the modern-day Gulf of Mexico. The Western Interior Seaway was created during one of the greatest transgression events of all time. In paleogeography, a transgression event is where the world’s sea levels rise. This can be caused by melting of icecaps, but in this case, the icecaps were already melted, and the transgression was caused by seafloor
