Eighty million years ago, the mid-continent was covered by a warm, shallow, interior sea extending from the Arctic Ocean to the Gulf of Mexico which was at least 1000 miles wide at the present boundary between Canada and the United States. To the west, newly formed mountains were unstable. Earthquakes occurred frequently as volcanoes were formed. Volcanic ash and fine muds were carried by wind and water currents to accumulate as sediment at the bottom of the sea.

WESTERN INTERIOR SEAWAY
During Cretaceous times Manitoba was largely covered by a warm shallow sea called The Western Interior Seaway. Global temperatures were warmer, sea levels were higher and there was little, if any, permanent ice at the poles. Low-lying areas of the continents the world over were inundated by the sea. In North America, the Seaway stretched from the Gulf of Mexico to the Arctic, effectively dividing the continent into two vast islands and lasted for millions of years.

CLIMATE
The sea, referred to as the "Mid-Continental Seaway", must have provided a fairly stable environment for many aeons. The climate of the time was much different from what it is today. There was little daily or seasonal temperature change. It remained remarkably stable as a tropical or sub-tropical area throughout the Upper Cretaceous Period.

ANIMAL LIFE
The animal life during the Upper Cretaceous period was teeming and varied. Reptiles, including four types of mosasaurs, plesiosaurs and great sea-turtles lived in abundance in this warm salty water. In addition, there were at least two species of birds, Hesperornis and Ichthyornis, as well as squids, sharks, and numerous species of
fish. All of these forms have been found as fossils in southern Manitoba as well as in Saskatchewan and Alberta.