Ripple Marks

Moving water forms ripples in sand, their size and spacing dictated by the flow and depth of the water. The ripples in these two photos are similar in scale and taken within a few hundred yards of one another, but the red ones are a trillion times older than the gray ones.

The red ripples are in sedimentary rocks of the Belt Series, deposited over a billion years ago in a shallow sea in what is now western Montana. They were brought here by the railroad from the Rockies to repair damaged portions of the revetment. The ripples in the wet sand on the beach were also formed under shallow water, but probably less than a couple hours ago.