Basin (geology)
Starting around 16 million years ago in the Miocene, and continuing into the present, a large part of the North American Plate has been stretched by being pulled apart.p611 The result has been the creation of a large and still-growing region of relatively thin crust; the region grew an average of  per year initially and then slowed to  per year in the last 5 million years. Geologists call this region the Basin and Range Province.