The continents’ shorelines changed constantly. Tectonic movement formed the first mountain peaks in the western part of North America. A huge inland sea separated these emerging mountains from the Appalachians. As a result, the Arctic Ocean was linked to the Gulf of Mexico through the continent’s interior.

There was much more water available because the polar caps were almost non- existent. Indeed, the forms of animal and plant life alive back then suggest temperatures were warmer and more stable than today.
Canadian Heritage Information Network
Canadian Heritage Information Network, Canadian Museum of Nature, Musée du Séminaire de Sherbrooke, Royal Tyrrell Museum

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