The Wanapum Basalt is made up of the Eckler Mountain Member (15.6 million years ago), the Frenchman Springs Member (15.5 million years ago), the Roza Member (14.9 million years ago) and the Priest Rapids Member (14.5 million years ago).
Der Wanapum Basalt besteht aus den Einheiten des Eckler Mountain Member (15,6 Millionen Jahre alt), des Frenchmen Springs Member (15,5 Millionen Jahre alt), des Roza Member (14,9 Millionen Jahre alt) und des Priest Rapids Member (14,5 Millionen Jahre alt).