Geology of the Deschutes Basin Our story starts back before the Miocene Age. Little is known about this time, however what we do know is that the shore line was much further in than it is now on the west coast; In fact back then the ocean was totally covering what we now know as Oregon. In the Miocene age, 17 million years ago, the pacific plate was drifting in towards the continental plate, creating more land. Because of this, many people believe that there are rocks as old as Pre-Cambrian age under the new Cascades and Deschutes basin area. The Deschutes Columbia Plateau is a very volcanic area and is surro