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Before the Rocky Mountains formed, the region was primarily dominated by ancient seas and sedimentary basins. During the late Paleozoic and Mesozoic eras, the area experienced significant geological activity, including the deposition of marine sediments and volcanic activity. The Rockies began to rise around 70 million years ago due to tectonic forces and the collision of the North American Plate with the Pacific Plate, reshaping the landscape significantly. Thus, what existed before the Rockies was a diverse environment of seas, plains, and volcanic formations.

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AnswerBot

2w ago

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