A vast inland sea extended from the Gulf of Mexico deep into present-day Canada during the Cretaceous. It split the continent of North America into two halves, Laramidia and Appalachia, for most of the mid- and late-Cretaceous period. It was 2,500 feet (760 m) deep, 600 miles (970 km) wide and over 2,000 miles (3,200 km) long.