Five to twenty-four million years ago erosion of the eastern front of the Rocky Mountains brought sand, gravel and other sediments to the low lands.
(Five to twenty-four million years ago erosion of the eastern front of the Rocky Mountains; brought; sand, gravel and other sediments; to the low lands)
Five to twenty-four million years ago erosion of the eastern front of the Rocky Mountains
brought
sand, gravel and other sediments to the low lands