Rocky Mountains Form (about 55 MYA)
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The Rocky Mountains stretch from Canada to New Mexico. In the south, an older mountain range was formed 300 million years ago, then eroded away. The rocks of that older range were reformed into the Rocky Mountains. The Rocky Mountains took shape during an intense period of plate tectonic activity that resulted in much of the rugged landscape of the western North America.
Himalayas Form (about 35 MYA)
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The Himalayas are known to be youngfold mountains. Young, because these have been formed relatively recently in the earth's history, compared to older mountain ranges like the Aravallis in India, and the Appalachian in the USA. They are known as fold mountains because the mountains extend for 2500 km in length in a series of parallel ridges or folds.