The classic topography question - which way does the river flow?  It’s a simple concept, really.  It’s called “The Rule of V’s” which means that when contour lines form a series of en echelon V’s, they will always point UPstream.  I know it was hard for me to grasp this and remember it when I was in intro Geology, so I figured I might as well make it easier to understand with this nifty animation!  (Not to mention I’ll be teaching the topography and GIS lab for physical geology coming up soon!)

Made from scratch using SketchUp from Trimble (Formerly Google SketchUp) and Adobe Photoshop CS5.

EDIT: Updated to show cross-sectional profile.