Sedimentary rocks are normally deposited as horizonal layers. Even when folded or tilted by faulting the originally horizontal layering is obvious. Upon closer examination, however, you may see very fine layers (usually 1 to several mm thick) that are at an angle to the main bedding. These tilted layers contained within larger layers are termed cross bedding.

What a mouthful right?  As sandstone is formed, sand is laid down, either by prevailing wind current, or water current.  However, over geologic time, those currents shift, causing sand to be laid down in a different direction.  What you get is cross bedding.  I love all the cross bedding in Zion National Park and thought it would make for a good abstract photo.  To make this, I intentionally underexposed the photo by ~1 stop, to emphasize the shadows, then I converted to black and white in Photoshop and applied a very light tint to the image.

Cross bedding abstract, Zion National Park, January 2010

You can see all of my Zion National Park images here.